* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
*/
#include <linux/ring_buffer.h>
+#include <linux/trace_clock.h>
+#include <linux/ftrace_irq.h>
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
+#include <linux/hardirq.h>
+#include <linux/kmemcheck.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/mutex.h>
-#include <linux/sched.h> /* used for sched_clock() (for now) */
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/list.h>
+#include <linux/cpu.h>
#include <linux/fs.h>
-/* Up this if you want to test the TIME_EXTENTS and normalization */
-#define DEBUG_SHIFT 0
+#include "trace.h"
-/* FIXME!!! */
-u64 ring_buffer_time_stamp(int cpu)
+/*
+ * The ring buffer header is special. We must manually up keep it.
+ */
+int ring_buffer_print_entry_header(struct trace_seq *s)
{
- /* shift to debug/test normalization and TIME_EXTENTS */
- return sched_clock() << DEBUG_SHIFT;
+ int ret;
+
+ ret = trace_seq_printf(s, "# compressed entry header\n");
+ ret = trace_seq_printf(s, "\ttype_len : 5 bits\n");
+ ret = trace_seq_printf(s, "\ttime_delta : 27 bits\n");
+ ret = trace_seq_printf(s, "\tarray : 32 bits\n");
+ ret = trace_seq_printf(s, "\n");
+ ret = trace_seq_printf(s, "\tpadding : type == %d\n",
+ RINGBUF_TYPE_PADDING);
+ ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
+ RINGBUF_TYPE_TIME_EXTEND);
+ ret = trace_seq_printf(s, "\tdata max type_len == %d\n",
+ RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
+
+ return ret;
+}
+
+/*
+ * The ring buffer is made up of a list of pages. A separate list of pages is
+ * allocated for each CPU. A writer may only write to a buffer that is
+ * associated with the CPU it is currently executing on. A reader may read
+ * from any per cpu buffer.
+ *
+ * The reader is special. For each per cpu buffer, the reader has its own
+ * reader page. When a reader has read the entire reader page, this reader
+ * page is swapped with another page in the ring buffer.
+ *
+ * Now, as long as the writer is off the reader page, the reader can do what
+ * ever it wants with that page. The writer will never write to that page
+ * again (as long as it is out of the ring buffer).
+ *
+ * Here's some silly ASCII art.
+ *
+ * +------+
+ * |reader| RING BUFFER
+ * |page |
+ * +------+ +---+ +---+ +---+
+ * | |-->| |-->| |
+ * +---+ +---+ +---+
+ * ^ |
+ * | |
+ * +---------------+
+ *
+ *
+ * +------+
+ * |reader| RING BUFFER
+ * |page |------------------v
+ * +------+ +---+ +---+ +---+
+ * | |-->| |-->| |
+ * +---+ +---+ +---+
+ * ^ |
+ * | |
+ * +---------------+
+ *
+ *
+ * +------+
+ * |reader| RING BUFFER
+ * |page |------------------v
+ * +------+ +---+ +---+ +---+
+ * ^ | |-->| |-->| |
+ * | +---+ +---+ +---+
+ * | |
+ * | |
+ * +------------------------------+
+ *
+ *
+ * +------+
+ * |buffer| RING BUFFER
+ * |page |------------------v
+ * +------+ +---+ +---+ +---+
+ * ^ | | | |-->| |
+ * | New +---+ +---+ +---+
+ * | Reader------^ |
+ * | page |
+ * +------------------------------+
+ *
+ *
+ * After we make this swap, the reader can hand this page off to the splice
+ * code and be done with it. It can even allocate a new page if it needs to
+ * and swap that into the ring buffer.
+ *
+ * We will be using cmpxchg soon to make all this lockless.
+ *
+ */
+
+/*
+ * A fast way to enable or disable all ring buffers is to
+ * call tracing_on or tracing_off. Turning off the ring buffers
+ * prevents all ring buffers from being recorded to.
+ * Turning this switch on, makes it OK to write to the
+ * ring buffer, if the ring buffer is enabled itself.
+ *
+ * There's three layers that must be on in order to write
+ * to the ring buffer.
+ *
+ * 1) This global flag must be set.
+ * 2) The ring buffer must be enabled for recording.
+ * 3) The per cpu buffer must be enabled for recording.
+ *
+ * In case of an anomaly, this global flag has a bit set that
+ * will permantly disable all ring buffers.
+ */
+
+/*
+ * Global flag to disable all recording to ring buffers
+ * This has two bits: ON, DISABLED
+ *
+ * ON DISABLED
+ * ---- ----------
+ * 0 0 : ring buffers are off
+ * 1 0 : ring buffers are on
+ * X 1 : ring buffers are permanently disabled
+ */
+
+enum {
+ RB_BUFFERS_ON_BIT = 0,
+ RB_BUFFERS_DISABLED_BIT = 1,
+};
+
+enum {
+ RB_BUFFERS_ON = 1 << RB_BUFFERS_ON_BIT,
+ RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
+};
+
+static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
+
+#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
+
+/**
+ * tracing_on - enable all tracing buffers
+ *
+ * This function enables all tracing buffers that may have been
+ * disabled with tracing_off.
+ */
+void tracing_on(void)
+{
+ set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
}
+EXPORT_SYMBOL_GPL(tracing_on);
-void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
+/**
+ * tracing_off - turn off all tracing buffers
+ *
+ * This function stops all tracing buffers from recording data.
+ * It does not disable any overhead the tracers themselves may
+ * be causing. This function simply causes all recording to
+ * the ring buffers to fail.
+ */
+void tracing_off(void)
{
- /* Just stupid testing the normalize function and deltas */
- *ts >>= DEBUG_SHIFT;
+ clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
+}
+EXPORT_SYMBOL_GPL(tracing_off);
+
+/**
+ * tracing_off_permanent - permanently disable ring buffers
+ *
+ * This function, once called, will disable all ring buffers
+ * permanently.
+ */
+void tracing_off_permanent(void)
+{
+ set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
+}
+
+/**
+ * tracing_is_on - show state of ring buffers enabled
+ */
+int tracing_is_on(void)
+{
+ return ring_buffer_flags == RB_BUFFERS_ON;
}
+EXPORT_SYMBOL_GPL(tracing_is_on);
+
+#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
+#define RB_ALIGNMENT 4U
+#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
+#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
-#define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event))
-#define RB_ALIGNMENT_SHIFT 2
-#define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT)
-#define RB_MAX_SMALL_DATA 28
+/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
+#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
enum {
RB_LEN_TIME_EXTEND = 8,
RB_LEN_TIME_STAMP = 16,
};
-/* inline for ring buffer fast paths */
-static inline unsigned
-rb_event_length(struct ring_buffer_event *event)
+static inline int rb_null_event(struct ring_buffer_event *event)
+{
+ return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
+}
+
+static void rb_event_set_padding(struct ring_buffer_event *event)
+{
+ /* padding has a NULL time_delta */
+ event->type_len = RINGBUF_TYPE_PADDING;
+ event->time_delta = 0;
+}
+
+static unsigned
+rb_event_data_length(struct ring_buffer_event *event)
{
unsigned length;
- switch (event->type) {
+ if (event->type_len)
+ length = event->type_len * RB_ALIGNMENT;
+ else
+ length = event->array[0];
+ return length + RB_EVNT_HDR_SIZE;
+}
+
+/* inline for ring buffer fast paths */
+static unsigned
+rb_event_length(struct ring_buffer_event *event)
+{
+ switch (event->type_len) {
case RINGBUF_TYPE_PADDING:
- /* undefined */
- return -1;
+ if (rb_null_event(event))
+ /* undefined */
+ return -1;
+ return event->array[0] + RB_EVNT_HDR_SIZE;
case RINGBUF_TYPE_TIME_EXTEND:
return RB_LEN_TIME_EXTEND;
return RB_LEN_TIME_STAMP;
case RINGBUF_TYPE_DATA:
- if (event->len)
- length = event->len << RB_ALIGNMENT_SHIFT;
- else
- length = event->array[0];
- return length + RB_EVNT_HDR_SIZE;
+ return rb_event_data_length(event);
default:
BUG();
}
*/
unsigned ring_buffer_event_length(struct ring_buffer_event *event)
{
- return rb_event_length(event);
+ unsigned length = rb_event_length(event);
+ if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
+ return length;
+ length -= RB_EVNT_HDR_SIZE;
+ if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
+ length -= sizeof(event->array[0]);
+ return length;
}
+EXPORT_SYMBOL_GPL(ring_buffer_event_length);
/* inline for ring buffer fast paths */
-static inline void *
+static void *
rb_event_data(struct ring_buffer_event *event)
{
- BUG_ON(event->type != RINGBUF_TYPE_DATA);
+ BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
/* If length is in len field, then array[0] has the data */
- if (event->len)
+ if (event->type_len)
return (void *)&event->array[0];
/* Otherwise length is in array[0] and array[1] has the data */
return (void *)&event->array[1];
{
return rb_event_data(event);
}
+EXPORT_SYMBOL_GPL(ring_buffer_event_data);
#define for_each_buffer_cpu(buffer, cpu) \
- for_each_cpu_mask(cpu, buffer->cpumask)
+ for_each_cpu(cpu, buffer->cpumask)
#define TS_SHIFT 27
#define TS_MASK ((1ULL << TS_SHIFT) - 1)
#define TS_DELTA_TEST (~TS_MASK)
+struct buffer_data_page {
+ u64 time_stamp; /* page time stamp */
+ local_t commit; /* write committed index */
+ unsigned char data[]; /* data of buffer page */
+};
+
/*
- * This hack stolen from mm/slob.c.
- * We can store per page timing information in the page frame of the page.
- * Thanks to Peter Zijlstra for suggesting this idea.
+ * Note, the buffer_page list must be first. The buffer pages
+ * are allocated in cache lines, which means that each buffer
+ * page will be at the beginning of a cache line, and thus
+ * the least significant bits will be zero. We use this to
+ * add flags in the list struct pointers, to make the ring buffer
+ * lockless.
*/
struct buffer_page {
- union {
- struct {
- unsigned long flags; /* mandatory */
- atomic_t _count; /* mandatory */
- u64 time_stamp; /* page time stamp */
- unsigned size; /* size of page data */
- struct list_head list; /* list of free pages */
- };
- struct page page;
- };
+ struct list_head list; /* list of buffer pages */
+ local_t write; /* index for next write */
+ unsigned read; /* index for next read */
+ local_t entries; /* entries on this page */
+ struct buffer_data_page *page; /* Actual data page */
};
/*
+ * The buffer page counters, write and entries, must be reset
+ * atomically when crossing page boundaries. To synchronize this
+ * update, two counters are inserted into the number. One is
+ * the actual counter for the write position or count on the page.
+ *
+ * The other is a counter of updaters. Before an update happens
+ * the update partition of the counter is incremented. This will
+ * allow the updater to update the counter atomically.
+ *
+ * The counter is 20 bits, and the state data is 12.
+ */
+#define RB_WRITE_MASK 0xfffff
+#define RB_WRITE_INTCNT (1 << 20)
+
+static void rb_init_page(struct buffer_data_page *bpage)
+{
+ local_set(&bpage->commit, 0);
+}
+
+/**
+ * ring_buffer_page_len - the size of data on the page.
+ * @page: The page to read
+ *
+ * Returns the amount of data on the page, including buffer page header.
+ */
+size_t ring_buffer_page_len(void *page)
+{
+ return local_read(&((struct buffer_data_page *)page)->commit)
+ + BUF_PAGE_HDR_SIZE;
+}
+
+/*
* Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
* this issue out.
*/
-static inline void free_buffer_page(struct buffer_page *bpage)
+static void free_buffer_page(struct buffer_page *bpage)
{
- reset_page_mapcount(&bpage->page);
- bpage->page.mapping = NULL;
- __free_page(&bpage->page);
+ free_page((unsigned long)bpage->page);
+ kfree(bpage);
}
/*
return 0;
}
-#define BUF_PAGE_SIZE PAGE_SIZE
+#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
+
+/* Max payload is BUF_PAGE_SIZE - header (8bytes) */
+#define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2))
+
+/* Max number of timestamps that can fit on a page */
+#define RB_TIMESTAMPS_PER_PAGE (BUF_PAGE_SIZE / RB_LEN_TIME_STAMP)
+
+int ring_buffer_print_page_header(struct trace_seq *s)
+{
+ struct buffer_data_page field;
+ int ret;
+
+ ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
+ "offset:0;\tsize:%u;\n",
+ (unsigned int)sizeof(field.time_stamp));
+
+ ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
+ "offset:%u;\tsize:%u;\n",
+ (unsigned int)offsetof(typeof(field), commit),
+ (unsigned int)sizeof(field.commit));
+
+ ret = trace_seq_printf(s, "\tfield: char data;\t"
+ "offset:%u;\tsize:%u;\n",
+ (unsigned int)offsetof(typeof(field), data),
+ (unsigned int)BUF_PAGE_SIZE);
+
+ return ret;
+}
/*
* head_page == tail_page && head == tail then buffer is empty.
struct ring_buffer_per_cpu {
int cpu;
struct ring_buffer *buffer;
- spinlock_t lock;
+ spinlock_t reader_lock; /* serialize readers */
+ raw_spinlock_t lock;
struct lock_class_key lock_key;
- struct list_head pages;
- unsigned long head; /* read from head */
- unsigned long tail; /* write to tail */
- struct buffer_page *head_page;
- struct buffer_page *tail_page;
- unsigned long overrun;
- unsigned long entries;
+ struct list_head *pages;
+ struct buffer_page *head_page; /* read from head */
+ struct buffer_page *tail_page; /* write to tail */
+ struct buffer_page *commit_page; /* committed pages */
+ struct buffer_page *reader_page;
+ local_t commit_overrun;
+ local_t overrun;
+ local_t entries;
+ local_t committing;
+ local_t commits;
+ unsigned long read;
u64 write_stamp;
u64 read_stamp;
atomic_t record_disabled;
};
struct ring_buffer {
- unsigned long size;
unsigned pages;
unsigned flags;
int cpus;
- cpumask_t cpumask;
atomic_t record_disabled;
+ cpumask_var_t cpumask;
+
+ struct lock_class_key *reader_lock_key;
struct mutex mutex;
struct ring_buffer_per_cpu **buffers;
+
+#ifdef CONFIG_HOTPLUG_CPU
+ struct notifier_block cpu_notify;
+#endif
+ u64 (*clock)(void);
};
struct ring_buffer_iter {
u64 read_stamp;
};
-#define RB_WARN_ON(buffer, cond) \
- if (unlikely(cond)) { \
- atomic_inc(&buffer->record_disabled); \
- WARN_ON(1); \
- return -1; \
+/* buffer may be either ring_buffer or ring_buffer_per_cpu */
+#define RB_WARN_ON(b, cond) \
+ ({ \
+ int _____ret = unlikely(cond); \
+ if (_____ret) { \
+ if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
+ struct ring_buffer_per_cpu *__b = \
+ (void *)b; \
+ atomic_inc(&__b->buffer->record_disabled); \
+ } else \
+ atomic_inc(&b->record_disabled); \
+ WARN_ON(1); \
+ } \
+ _____ret; \
+ })
+
+/* Up this if you want to test the TIME_EXTENTS and normalization */
+#define DEBUG_SHIFT 0
+
+static inline u64 rb_time_stamp(struct ring_buffer *buffer, int cpu)
+{
+ /* shift to debug/test normalization and TIME_EXTENTS */
+ return buffer->clock() << DEBUG_SHIFT;
+}
+
+u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
+{
+ u64 time;
+
+ preempt_disable_notrace();
+ time = rb_time_stamp(buffer, cpu);
+ preempt_enable_no_resched_notrace();
+
+ return time;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
+
+void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
+ int cpu, u64 *ts)
+{
+ /* Just stupid testing the normalize function and deltas */
+ *ts >>= DEBUG_SHIFT;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
+
+/*
+ * Making the ring buffer lockless makes things tricky.
+ * Although writes only happen on the CPU that they are on,
+ * and they only need to worry about interrupts. Reads can
+ * happen on any CPU.
+ *
+ * The reader page is always off the ring buffer, but when the
+ * reader finishes with a page, it needs to swap its page with
+ * a new one from the buffer. The reader needs to take from
+ * the head (writes go to the tail). But if a writer is in overwrite
+ * mode and wraps, it must push the head page forward.
+ *
+ * Here lies the problem.
+ *
+ * The reader must be careful to replace only the head page, and
+ * not another one. As described at the top of the file in the
+ * ASCII art, the reader sets its old page to point to the next
+ * page after head. It then sets the page after head to point to
+ * the old reader page. But if the writer moves the head page
+ * during this operation, the reader could end up with the tail.
+ *
+ * We use cmpxchg to help prevent this race. We also do something
+ * special with the page before head. We set the LSB to 1.
+ *
+ * When the writer must push the page forward, it will clear the
+ * bit that points to the head page, move the head, and then set
+ * the bit that points to the new head page.
+ *
+ * We also don't want an interrupt coming in and moving the head
+ * page on another writer. Thus we use the second LSB to catch
+ * that too. Thus:
+ *
+ * head->list->prev->next bit 1 bit 0
+ * ------- -------
+ * Normal page 0 0
+ * Points to head page 0 1
+ * New head page 1 0
+ *
+ * Note we can not trust the prev pointer of the head page, because:
+ *
+ * +----+ +-----+ +-----+
+ * | |------>| T |---X--->| N |
+ * | |<------| | | |
+ * +----+ +-----+ +-----+
+ * ^ ^ |
+ * | +-----+ | |
+ * +----------| R |----------+ |
+ * | |<-----------+
+ * +-----+
+ *
+ * Key: ---X--> HEAD flag set in pointer
+ * T Tail page
+ * R Reader page
+ * N Next page
+ *
+ * (see __rb_reserve_next() to see where this happens)
+ *
+ * What the above shows is that the reader just swapped out
+ * the reader page with a page in the buffer, but before it
+ * could make the new header point back to the new page added
+ * it was preempted by a writer. The writer moved forward onto
+ * the new page added by the reader and is about to move forward
+ * again.
+ *
+ * You can see, it is legitimate for the previous pointer of
+ * the head (or any page) not to point back to itself. But only
+ * temporarially.
+ */
+
+#define RB_PAGE_NORMAL 0UL
+#define RB_PAGE_HEAD 1UL
+#define RB_PAGE_UPDATE 2UL
+
+
+#define RB_FLAG_MASK 3UL
+
+/* PAGE_MOVED is not part of the mask */
+#define RB_PAGE_MOVED 4UL
+
+/*
+ * rb_list_head - remove any bit
+ */
+static struct list_head *rb_list_head(struct list_head *list)
+{
+ unsigned long val = (unsigned long)list;
+
+ return (struct list_head *)(val & ~RB_FLAG_MASK);
+}
+
+/*
+ * rb_is_head_page - test if the give page is the head page
+ *
+ * Because the reader may move the head_page pointer, we can
+ * not trust what the head page is (it may be pointing to
+ * the reader page). But if the next page is a header page,
+ * its flags will be non zero.
+ */
+static int inline
+rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *page, struct list_head *list)
+{
+ unsigned long val;
+
+ val = (unsigned long)list->next;
+
+ if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
+ return RB_PAGE_MOVED;
+
+ return val & RB_FLAG_MASK;
+}
+
+/*
+ * rb_is_reader_page
+ *
+ * The unique thing about the reader page, is that, if the
+ * writer is ever on it, the previous pointer never points
+ * back to the reader page.
+ */
+static int rb_is_reader_page(struct buffer_page *page)
+{
+ struct list_head *list = page->list.prev;
+
+ return rb_list_head(list->next) != &page->list;
+}
+
+/*
+ * rb_set_list_to_head - set a list_head to be pointing to head.
+ */
+static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer,
+ struct list_head *list)
+{
+ unsigned long *ptr;
+
+ ptr = (unsigned long *)&list->next;
+ *ptr |= RB_PAGE_HEAD;
+ *ptr &= ~RB_PAGE_UPDATE;
+}
+
+/*
+ * rb_head_page_activate - sets up head page
+ */
+static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct buffer_page *head;
+
+ head = cpu_buffer->head_page;
+ if (!head)
+ return;
+
+ /*
+ * Set the previous list pointer to have the HEAD flag.
+ */
+ rb_set_list_to_head(cpu_buffer, head->list.prev);
+}
+
+static void rb_list_head_clear(struct list_head *list)
+{
+ unsigned long *ptr = (unsigned long *)&list->next;
+
+ *ptr &= ~RB_FLAG_MASK;
+}
+
+/*
+ * rb_head_page_dactivate - clears head page ptr (for free list)
+ */
+static void
+rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct list_head *hd;
+
+ /* Go through the whole list and clear any pointers found. */
+ rb_list_head_clear(cpu_buffer->pages);
+
+ list_for_each(hd, cpu_buffer->pages)
+ rb_list_head_clear(hd);
+}
+
+static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *head,
+ struct buffer_page *prev,
+ int old_flag, int new_flag)
+{
+ struct list_head *list;
+ unsigned long val = (unsigned long)&head->list;
+ unsigned long ret;
+
+ list = &prev->list;
+
+ val &= ~RB_FLAG_MASK;
+
+ ret = cmpxchg((unsigned long *)&list->next,
+ val | old_flag, val | new_flag);
+
+ /* check if the reader took the page */
+ if ((ret & ~RB_FLAG_MASK) != val)
+ return RB_PAGE_MOVED;
+
+ return ret & RB_FLAG_MASK;
+}
+
+static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *head,
+ struct buffer_page *prev,
+ int old_flag)
+{
+ return rb_head_page_set(cpu_buffer, head, prev,
+ old_flag, RB_PAGE_UPDATE);
+}
+
+static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *head,
+ struct buffer_page *prev,
+ int old_flag)
+{
+ return rb_head_page_set(cpu_buffer, head, prev,
+ old_flag, RB_PAGE_HEAD);
+}
+
+static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *head,
+ struct buffer_page *prev,
+ int old_flag)
+{
+ return rb_head_page_set(cpu_buffer, head, prev,
+ old_flag, RB_PAGE_NORMAL);
+}
+
+static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page **bpage)
+{
+ struct list_head *p = rb_list_head((*bpage)->list.next);
+
+ *bpage = list_entry(p, struct buffer_page, list);
+}
+
+static struct buffer_page *
+rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct buffer_page *head;
+ struct buffer_page *page;
+ struct list_head *list;
+ int i;
+
+ if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
+ return NULL;
+
+ /* sanity check */
+ list = cpu_buffer->pages;
+ if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
+ return NULL;
+
+ page = head = cpu_buffer->head_page;
+ /*
+ * It is possible that the writer moves the header behind
+ * where we started, and we miss in one loop.
+ * A second loop should grab the header, but we'll do
+ * three loops just because I'm paranoid.
+ */
+ for (i = 0; i < 3; i++) {
+ do {
+ if (rb_is_head_page(cpu_buffer, page, page->list.prev)) {
+ cpu_buffer->head_page = page;
+ return page;
+ }
+ rb_inc_page(cpu_buffer, &page);
+ } while (page != head);
+ }
+
+ RB_WARN_ON(cpu_buffer, 1);
+
+ return NULL;
+}
+
+static int rb_head_page_replace(struct buffer_page *old,
+ struct buffer_page *new)
+{
+ unsigned long *ptr = (unsigned long *)&old->list.prev->next;
+ unsigned long val;
+ unsigned long ret;
+
+ val = *ptr & ~RB_FLAG_MASK;
+ val |= RB_PAGE_HEAD;
+
+ ret = cmpxchg(ptr, val, (unsigned long)&new->list);
+
+ return ret == val;
+}
+
+/*
+ * rb_tail_page_update - move the tail page forward
+ *
+ * Returns 1 if moved tail page, 0 if someone else did.
+ */
+static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *tail_page,
+ struct buffer_page *next_page)
+{
+ struct buffer_page *old_tail;
+ unsigned long old_entries;
+ unsigned long old_write;
+ int ret = 0;
+
+ /*
+ * The tail page now needs to be moved forward.
+ *
+ * We need to reset the tail page, but without messing
+ * with possible erasing of data brought in by interrupts
+ * that have moved the tail page and are currently on it.
+ *
+ * We add a counter to the write field to denote this.
+ */
+ old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
+ old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
+
+ /*
+ * Just make sure we have seen our old_write and synchronize
+ * with any interrupts that come in.
+ */
+ barrier();
+
+ /*
+ * If the tail page is still the same as what we think
+ * it is, then it is up to us to update the tail
+ * pointer.
+ */
+ if (tail_page == cpu_buffer->tail_page) {
+ /* Zero the write counter */
+ unsigned long val = old_write & ~RB_WRITE_MASK;
+ unsigned long eval = old_entries & ~RB_WRITE_MASK;
+
+ /*
+ * This will only succeed if an interrupt did
+ * not come in and change it. In which case, we
+ * do not want to modify it.
+ *
+ * We add (void) to let the compiler know that we do not care
+ * about the return value of these functions. We use the
+ * cmpxchg to only update if an interrupt did not already
+ * do it for us. If the cmpxchg fails, we don't care.
+ */
+ (void)local_cmpxchg(&next_page->write, old_write, val);
+ (void)local_cmpxchg(&next_page->entries, old_entries, eval);
+
+ /*
+ * No need to worry about races with clearing out the commit.
+ * it only can increment when a commit takes place. But that
+ * only happens in the outer most nested commit.
+ */
+ local_set(&next_page->page->commit, 0);
+
+ old_tail = cmpxchg(&cpu_buffer->tail_page,
+ tail_page, next_page);
+
+ if (old_tail == tail_page)
+ ret = 1;
}
+ return ret;
+}
+
+static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *bpage)
+{
+ unsigned long val = (unsigned long)bpage;
+
+ if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK))
+ return 1;
+
+ return 0;
+}
+
+/**
+ * rb_check_list - make sure a pointer to a list has the last bits zero
+ */
+static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer,
+ struct list_head *list)
+{
+ if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev))
+ return 1;
+ if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next))
+ return 1;
+ return 0;
+}
+
/**
* check_pages - integrity check of buffer pages
* @cpu_buffer: CPU buffer with pages to test
*
- * As a safty measure we check to make sure the data pages have not
+ * As a safety measure we check to make sure the data pages have not
* been corrupted.
*/
static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
{
- struct list_head *head = &cpu_buffer->pages;
- struct buffer_page *page, *tmp;
+ struct list_head *head = cpu_buffer->pages;
+ struct buffer_page *bpage, *tmp;
+
+ rb_head_page_deactivate(cpu_buffer);
- RB_WARN_ON(cpu_buffer, head->next->prev != head);
- RB_WARN_ON(cpu_buffer, head->prev->next != head);
+ if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
+ return -1;
+ if (RB_WARN_ON(cpu_buffer, head->prev->next != head))
+ return -1;
- list_for_each_entry_safe(page, tmp, head, list) {
- RB_WARN_ON(cpu_buffer, page->list.next->prev != &page->list);
- RB_WARN_ON(cpu_buffer, page->list.prev->next != &page->list);
+ if (rb_check_list(cpu_buffer, head))
+ return -1;
+
+ list_for_each_entry_safe(bpage, tmp, head, list) {
+ if (RB_WARN_ON(cpu_buffer,
+ bpage->list.next->prev != &bpage->list))
+ return -1;
+ if (RB_WARN_ON(cpu_buffer,
+ bpage->list.prev->next != &bpage->list))
+ return -1;
+ if (rb_check_list(cpu_buffer, &bpage->list))
+ return -1;
}
- return 0;
-}
+ rb_head_page_activate(cpu_buffer);
-static unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer)
-{
- return cpu_buffer->head_page->size;
+ return 0;
}
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
unsigned nr_pages)
{
- struct list_head *head = &cpu_buffer->pages;
- struct buffer_page *page, *tmp;
+ struct buffer_page *bpage, *tmp;
unsigned long addr;
LIST_HEAD(pages);
unsigned i;
+ WARN_ON(!nr_pages);
+
for (i = 0; i < nr_pages; i++) {
+ bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
+ GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
+ if (!bpage)
+ goto free_pages;
+
+ rb_check_bpage(cpu_buffer, bpage);
+
+ list_add(&bpage->list, &pages);
+
addr = __get_free_page(GFP_KERNEL);
if (!addr)
goto free_pages;
- page = (struct buffer_page *)virt_to_page(addr);
- list_add(&page->list, &pages);
+ bpage->page = (void *)addr;
+ rb_init_page(bpage->page);
}
- list_splice(&pages, head);
+ /*
+ * The ring buffer page list is a circular list that does not
+ * start and end with a list head. All page list items point to
+ * other pages.
+ */
+ cpu_buffer->pages = pages.next;
+ list_del(&pages);
rb_check_pages(cpu_buffer);
return 0;
free_pages:
- list_for_each_entry_safe(page, tmp, &pages, list) {
- list_del_init(&page->list);
- free_buffer_page(page);
+ list_for_each_entry_safe(bpage, tmp, &pages, list) {
+ list_del_init(&bpage->list);
+ free_buffer_page(bpage);
}
return -ENOMEM;
}
rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
+ struct buffer_page *bpage;
+ unsigned long addr;
int ret;
cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
cpu_buffer->cpu = cpu;
cpu_buffer->buffer = buffer;
- spin_lock_init(&cpu_buffer->lock);
- INIT_LIST_HEAD(&cpu_buffer->pages);
+ spin_lock_init(&cpu_buffer->reader_lock);
+ lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
+ cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
+
+ bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
+ GFP_KERNEL, cpu_to_node(cpu));
+ if (!bpage)
+ goto fail_free_buffer;
+
+ rb_check_bpage(cpu_buffer, bpage);
+
+ cpu_buffer->reader_page = bpage;
+ addr = __get_free_page(GFP_KERNEL);
+ if (!addr)
+ goto fail_free_reader;
+ bpage->page = (void *)addr;
+ rb_init_page(bpage->page);
+
+ INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
ret = rb_allocate_pages(cpu_buffer, buffer->pages);
if (ret < 0)
- goto fail_free_buffer;
+ goto fail_free_reader;
cpu_buffer->head_page
- = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
- cpu_buffer->tail_page
- = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
+ = list_entry(cpu_buffer->pages, struct buffer_page, list);
+ cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
+
+ rb_head_page_activate(cpu_buffer);
return cpu_buffer;
+ fail_free_reader:
+ free_buffer_page(cpu_buffer->reader_page);
+
fail_free_buffer:
kfree(cpu_buffer);
return NULL;
static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
{
- struct list_head *head = &cpu_buffer->pages;
- struct buffer_page *page, *tmp;
+ struct list_head *head = cpu_buffer->pages;
+ struct buffer_page *bpage, *tmp;
+
+ free_buffer_page(cpu_buffer->reader_page);
- list_for_each_entry_safe(page, tmp, head, list) {
- list_del_init(&page->list);
- free_buffer_page(page);
+ rb_head_page_deactivate(cpu_buffer);
+
+ if (head) {
+ list_for_each_entry_safe(bpage, tmp, head, list) {
+ list_del_init(&bpage->list);
+ free_buffer_page(bpage);
+ }
+ bpage = list_entry(head, struct buffer_page, list);
+ free_buffer_page(bpage);
}
+
kfree(cpu_buffer);
}
-/*
- * Causes compile errors if the struct buffer_page gets bigger
- * than the struct page.
- */
-extern int ring_buffer_page_too_big(void);
+#ifdef CONFIG_HOTPLUG_CPU
+static int rb_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu);
+#endif
/**
* ring_buffer_alloc - allocate a new ring_buffer
- * @size: the size in bytes that is needed.
+ * @size: the size in bytes per cpu that is needed.
* @flags: attributes to set for the ring buffer.
*
* Currently the only flag that is available is the RB_FL_OVERWRITE
* when the buffer wraps. If this flag is not set, the buffer will
* drop data when the tail hits the head.
*/
-struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags)
+struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
+ struct lock_class_key *key)
{
struct ring_buffer *buffer;
int bsize;
int cpu;
- /* Paranoid! Optimizes out when all is well */
- if (sizeof(struct buffer_page) > sizeof(struct page))
- ring_buffer_page_too_big();
-
-
/* keep it in its own cache line */
buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
GFP_KERNEL);
if (!buffer)
return NULL;
+ if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
+ goto fail_free_buffer;
+
buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
buffer->flags = flags;
+ buffer->clock = trace_clock_local;
+ buffer->reader_lock_key = key;
/* need at least two pages */
- if (buffer->pages == 1)
- buffer->pages++;
+ if (buffer->pages < 2)
+ buffer->pages = 2;
- buffer->cpumask = cpu_possible_map;
+ /*
+ * In case of non-hotplug cpu, if the ring-buffer is allocated
+ * in early initcall, it will not be notified of secondary cpus.
+ * In that off case, we need to allocate for all possible cpus.
+ */
+#ifdef CONFIG_HOTPLUG_CPU
+ get_online_cpus();
+ cpumask_copy(buffer->cpumask, cpu_online_mask);
+#else
+ cpumask_copy(buffer->cpumask, cpu_possible_mask);
+#endif
buffer->cpus = nr_cpu_ids;
bsize = sizeof(void *) * nr_cpu_ids;
buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
GFP_KERNEL);
if (!buffer->buffers)
- goto fail_free_buffer;
+ goto fail_free_cpumask;
for_each_buffer_cpu(buffer, cpu) {
buffer->buffers[cpu] =
goto fail_free_buffers;
}
+#ifdef CONFIG_HOTPLUG_CPU
+ buffer->cpu_notify.notifier_call = rb_cpu_notify;
+ buffer->cpu_notify.priority = 0;
+ register_cpu_notifier(&buffer->cpu_notify);
+#endif
+
+ put_online_cpus();
mutex_init(&buffer->mutex);
return buffer;
}
kfree(buffer->buffers);
+ fail_free_cpumask:
+ free_cpumask_var(buffer->cpumask);
+ put_online_cpus();
+
fail_free_buffer:
kfree(buffer);
return NULL;
}
+EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
/**
* ring_buffer_free - free a ring buffer.
{
int cpu;
+ get_online_cpus();
+
+#ifdef CONFIG_HOTPLUG_CPU
+ unregister_cpu_notifier(&buffer->cpu_notify);
+#endif
+
for_each_buffer_cpu(buffer, cpu)
rb_free_cpu_buffer(buffer->buffers[cpu]);
+ put_online_cpus();
+
+ kfree(buffer->buffers);
+ free_cpumask_var(buffer->cpumask);
+
kfree(buffer);
}
+EXPORT_SYMBOL_GPL(ring_buffer_free);
+
+void ring_buffer_set_clock(struct ring_buffer *buffer,
+ u64 (*clock)(void))
+{
+ buffer->clock = clock;
+}
static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
static void
rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
{
- struct buffer_page *page;
+ struct buffer_page *bpage;
struct list_head *p;
unsigned i;
atomic_inc(&cpu_buffer->record_disabled);
synchronize_sched();
+ rb_head_page_deactivate(cpu_buffer);
+
for (i = 0; i < nr_pages; i++) {
- BUG_ON(list_empty(&cpu_buffer->pages));
- p = cpu_buffer->pages.next;
- page = list_entry(p, struct buffer_page, list);
- list_del_init(&page->list);
- free_buffer_page(page);
+ if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)))
+ return;
+ p = cpu_buffer->pages->next;
+ bpage = list_entry(p, struct buffer_page, list);
+ list_del_init(&bpage->list);
+ free_buffer_page(bpage);
}
- BUG_ON(list_empty(&cpu_buffer->pages));
+ if (RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)))
+ return;
rb_reset_cpu(cpu_buffer);
rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
struct list_head *pages, unsigned nr_pages)
{
- struct buffer_page *page;
+ struct buffer_page *bpage;
struct list_head *p;
unsigned i;
atomic_inc(&cpu_buffer->record_disabled);
synchronize_sched();
+ spin_lock_irq(&cpu_buffer->reader_lock);
+ rb_head_page_deactivate(cpu_buffer);
+
for (i = 0; i < nr_pages; i++) {
- BUG_ON(list_empty(pages));
+ if (RB_WARN_ON(cpu_buffer, list_empty(pages)))
+ return;
p = pages->next;
- page = list_entry(p, struct buffer_page, list);
- list_del_init(&page->list);
- list_add_tail(&page->list, &cpu_buffer->pages);
+ bpage = list_entry(p, struct buffer_page, list);
+ list_del_init(&bpage->list);
+ list_add_tail(&bpage->list, cpu_buffer->pages);
}
rb_reset_cpu(cpu_buffer);
+ spin_unlock_irq(&cpu_buffer->reader_lock);
rb_check_pages(cpu_buffer);
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned nr_pages, rm_pages, new_pages;
- struct buffer_page *page, *tmp;
+ struct buffer_page *bpage, *tmp;
unsigned long buffer_size;
unsigned long addr;
LIST_HEAD(pages);
int i, cpu;
+ /*
+ * Always succeed at resizing a non-existent buffer:
+ */
+ if (!buffer)
+ return size;
+
size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
size *= BUF_PAGE_SIZE;
buffer_size = buffer->pages * BUF_PAGE_SIZE;
return size;
mutex_lock(&buffer->mutex);
+ get_online_cpus();
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
if (size < buffer_size) {
/* easy case, just free pages */
- BUG_ON(nr_pages >= buffer->pages);
+ if (RB_WARN_ON(buffer, nr_pages >= buffer->pages))
+ goto out_fail;
rm_pages = buffer->pages - nr_pages;
* add these pages to the cpu_buffers. Otherwise we just free
* them all and return -ENOMEM;
*/
- BUG_ON(nr_pages <= buffer->pages);
+ if (RB_WARN_ON(buffer, nr_pages <= buffer->pages))
+ goto out_fail;
+
new_pages = nr_pages - buffer->pages;
for_each_buffer_cpu(buffer, cpu) {
for (i = 0; i < new_pages; i++) {
+ bpage = kzalloc_node(ALIGN(sizeof(*bpage),
+ cache_line_size()),
+ GFP_KERNEL, cpu_to_node(cpu));
+ if (!bpage)
+ goto free_pages;
+ list_add(&bpage->list, &pages);
addr = __get_free_page(GFP_KERNEL);
if (!addr)
goto free_pages;
- page = (struct buffer_page *)virt_to_page(addr);
- list_add(&page->list, &pages);
+ bpage->page = (void *)addr;
+ rb_init_page(bpage->page);
}
}
rb_insert_pages(cpu_buffer, &pages, new_pages);
}
- BUG_ON(!list_empty(&pages));
+ if (RB_WARN_ON(buffer, !list_empty(&pages)))
+ goto out_fail;
out:
buffer->pages = nr_pages;
+ put_online_cpus();
mutex_unlock(&buffer->mutex);
return size;
free_pages:
- list_for_each_entry_safe(page, tmp, &pages, list) {
- list_del_init(&page->list);
- free_buffer_page(page);
+ list_for_each_entry_safe(bpage, tmp, &pages, list) {
+ list_del_init(&bpage->list);
+ free_buffer_page(bpage);
}
+ put_online_cpus();
+ mutex_unlock(&buffer->mutex);
return -ENOMEM;
-}
-static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
-{
- return cpu_buffer->head_page == cpu_buffer->tail_page &&
- cpu_buffer->head == cpu_buffer->tail;
+ /*
+ * Something went totally wrong, and we are too paranoid
+ * to even clean up the mess.
+ */
+ out_fail:
+ put_online_cpus();
+ mutex_unlock(&buffer->mutex);
+ return -1;
}
+EXPORT_SYMBOL_GPL(ring_buffer_resize);
-static inline int rb_null_event(struct ring_buffer_event *event)
+static inline void *
+__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
{
- return event->type == RINGBUF_TYPE_PADDING;
+ return bpage->data + index;
}
-static inline void *rb_page_index(struct buffer_page *page, unsigned index)
+static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
{
- void *addr = page_address(&page->page);
-
- return addr + index;
+ return bpage->page->data + index;
}
static inline struct ring_buffer_event *
-rb_head_event(struct ring_buffer_per_cpu *cpu_buffer)
+rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
{
- return rb_page_index(cpu_buffer->head_page,
- cpu_buffer->head);
+ return __rb_page_index(cpu_buffer->reader_page,
+ cpu_buffer->reader_page->read);
}
static inline struct ring_buffer_event *
rb_iter_head_event(struct ring_buffer_iter *iter)
{
- return rb_page_index(iter->head_page,
- iter->head);
+ return __rb_page_index(iter->head_page, iter->head);
}
-/*
- * When the tail hits the head and the buffer is in overwrite mode,
- * the head jumps to the next page and all content on the previous
- * page is discarded. But before doing so, we update the overrun
- * variable of the buffer.
- */
-static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
+static inline unsigned long rb_page_write(struct buffer_page *bpage)
{
- struct ring_buffer_event *event;
- unsigned long head;
-
- for (head = 0; head < rb_head_size(cpu_buffer);
- head += rb_event_length(event)) {
-
- event = rb_page_index(cpu_buffer->head_page, head);
- BUG_ON(rb_null_event(event));
- /* Only count data entries */
- if (event->type != RINGBUF_TYPE_DATA)
- continue;
- cpu_buffer->overrun++;
- cpu_buffer->entries--;
- }
+ return local_read(&bpage->write) & RB_WRITE_MASK;
}
-static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
- struct buffer_page **page)
+static inline unsigned rb_page_commit(struct buffer_page *bpage)
{
- struct list_head *p = (*page)->list.next;
+ return local_read(&bpage->page->commit);
+}
- if (p == &cpu_buffer->pages)
- p = p->next;
+static inline unsigned long rb_page_entries(struct buffer_page *bpage)
+{
+ return local_read(&bpage->entries) & RB_WRITE_MASK;
+}
- *page = list_entry(p, struct buffer_page, list);
+/* Size is determined by what has been commited */
+static inline unsigned rb_page_size(struct buffer_page *bpage)
+{
+ return rb_page_commit(bpage);
}
-static inline void
-rb_add_stamp(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts)
+static inline unsigned
+rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ return rb_page_commit(cpu_buffer->commit_page);
+}
+
+static inline unsigned
+rb_event_index(struct ring_buffer_event *event)
{
- cpu_buffer->tail_page->time_stamp = *ts;
- cpu_buffer->write_stamp = *ts;
+ unsigned long addr = (unsigned long)event;
+
+ return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE;
}
-static void rb_reset_read_page(struct ring_buffer_per_cpu *cpu_buffer)
+static inline int
+rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event)
{
- cpu_buffer->read_stamp = cpu_buffer->head_page->time_stamp;
- cpu_buffer->head = 0;
+ unsigned long addr = (unsigned long)event;
+ unsigned long index;
+
+ index = rb_event_index(event);
+ addr &= PAGE_MASK;
+
+ return cpu_buffer->commit_page->page == (void *)addr &&
+ rb_commit_index(cpu_buffer) == index;
}
static void
-rb_reset_iter_read_page(struct ring_buffer_iter *iter)
+rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ unsigned long max_count;
+
+ /*
+ * We only race with interrupts and NMIs on this CPU.
+ * If we own the commit event, then we can commit
+ * all others that interrupted us, since the interruptions
+ * are in stack format (they finish before they come
+ * back to us). This allows us to do a simple loop to
+ * assign the commit to the tail.
+ */
+ again:
+ max_count = cpu_buffer->buffer->pages * 100;
+
+ while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
+ if (RB_WARN_ON(cpu_buffer, !(--max_count)))
+ return;
+ if (RB_WARN_ON(cpu_buffer,
+ rb_is_reader_page(cpu_buffer->tail_page)))
+ return;
+ local_set(&cpu_buffer->commit_page->page->commit,
+ rb_page_write(cpu_buffer->commit_page));
+ rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
+ cpu_buffer->write_stamp =
+ cpu_buffer->commit_page->page->time_stamp;
+ /* add barrier to keep gcc from optimizing too much */
+ barrier();
+ }
+ while (rb_commit_index(cpu_buffer) !=
+ rb_page_write(cpu_buffer->commit_page)) {
+
+ local_set(&cpu_buffer->commit_page->page->commit,
+ rb_page_write(cpu_buffer->commit_page));
+ RB_WARN_ON(cpu_buffer,
+ local_read(&cpu_buffer->commit_page->page->commit) &
+ ~RB_WRITE_MASK);
+ barrier();
+ }
+
+ /* again, keep gcc from optimizing */
+ barrier();
+
+ /*
+ * If an interrupt came in just after the first while loop
+ * and pushed the tail page forward, we will be left with
+ * a dangling commit that will never go forward.
+ */
+ if (unlikely(cpu_buffer->commit_page != cpu_buffer->tail_page))
+ goto again;
+}
+
+static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
+ cpu_buffer->reader_page->read = 0;
+}
+
+static void rb_inc_iter(struct ring_buffer_iter *iter)
{
- iter->read_stamp = iter->head_page->time_stamp;
+ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+
+ /*
+ * The iterator could be on the reader page (it starts there).
+ * But the head could have moved, since the reader was
+ * found. Check for this case and assign the iterator
+ * to the head page instead of next.
+ */
+ if (iter->head_page == cpu_buffer->reader_page)
+ iter->head_page = rb_set_head_page(cpu_buffer);
+ else
+ rb_inc_page(cpu_buffer, &iter->head_page);
+
+ iter->read_stamp = iter->head_page->page->time_stamp;
iter->head = 0;
}
* and with this, we can determine what to place into the
* data field.
*/
-static inline void
+static void
rb_update_event(struct ring_buffer_event *event,
unsigned type, unsigned length)
{
- event->type = type;
+ event->type_len = type;
switch (type) {
case RINGBUF_TYPE_PADDING:
- break;
-
case RINGBUF_TYPE_TIME_EXTEND:
- event->len =
- (RB_LEN_TIME_EXTEND + (RB_ALIGNMENT-1))
- >> RB_ALIGNMENT_SHIFT;
- break;
-
case RINGBUF_TYPE_TIME_STAMP:
- event->len =
- (RB_LEN_TIME_STAMP + (RB_ALIGNMENT-1))
- >> RB_ALIGNMENT_SHIFT;
break;
- case RINGBUF_TYPE_DATA:
+ case 0:
length -= RB_EVNT_HDR_SIZE;
- if (length > RB_MAX_SMALL_DATA) {
- event->len = 0;
+ if (length > RB_MAX_SMALL_DATA)
event->array[0] = length;
- } else
- event->len =
- (length + (RB_ALIGNMENT-1))
- >> RB_ALIGNMENT_SHIFT;
+ else
+ event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
break;
default:
BUG();
}
}
-static inline unsigned rb_calculate_event_length(unsigned length)
+/*
+ * rb_handle_head_page - writer hit the head page
+ *
+ * Returns: +1 to retry page
+ * 0 to continue
+ * -1 on error
+ */
+static int
+rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *tail_page,
+ struct buffer_page *next_page)
+{
+ struct buffer_page *new_head;
+ int entries;
+ int type;
+ int ret;
+
+ entries = rb_page_entries(next_page);
+
+ /*
+ * The hard part is here. We need to move the head
+ * forward, and protect against both readers on
+ * other CPUs and writers coming in via interrupts.
+ */
+ type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
+ RB_PAGE_HEAD);
+
+ /*
+ * type can be one of four:
+ * NORMAL - an interrupt already moved it for us
+ * HEAD - we are the first to get here.
+ * UPDATE - we are the interrupt interrupting
+ * a current move.
+ * MOVED - a reader on another CPU moved the next
+ * pointer to its reader page. Give up
+ * and try again.
+ */
+
+ switch (type) {
+ case RB_PAGE_HEAD:
+ /*
+ * We changed the head to UPDATE, thus
+ * it is our responsibility to update
+ * the counters.
+ */
+ local_add(entries, &cpu_buffer->overrun);
+
+ /*
+ * The entries will be zeroed out when we move the
+ * tail page.
+ */
+
+ /* still more to do */
+ break;
+
+ case RB_PAGE_UPDATE:
+ /*
+ * This is an interrupt that interrupt the
+ * previous update. Still more to do.
+ */
+ break;
+ case RB_PAGE_NORMAL:
+ /*
+ * An interrupt came in before the update
+ * and processed this for us.
+ * Nothing left to do.
+ */
+ return 1;
+ case RB_PAGE_MOVED:
+ /*
+ * The reader is on another CPU and just did
+ * a swap with our next_page.
+ * Try again.
+ */
+ return 1;
+ default:
+ RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
+ return -1;
+ }
+
+ /*
+ * Now that we are here, the old head pointer is
+ * set to UPDATE. This will keep the reader from
+ * swapping the head page with the reader page.
+ * The reader (on another CPU) will spin till
+ * we are finished.
+ *
+ * We just need to protect against interrupts
+ * doing the job. We will set the next pointer
+ * to HEAD. After that, we set the old pointer
+ * to NORMAL, but only if it was HEAD before.
+ * otherwise we are an interrupt, and only
+ * want the outer most commit to reset it.
+ */
+ new_head = next_page;
+ rb_inc_page(cpu_buffer, &new_head);
+
+ ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
+ RB_PAGE_NORMAL);
+
+ /*
+ * Valid returns are:
+ * HEAD - an interrupt came in and already set it.
+ * NORMAL - One of two things:
+ * 1) We really set it.
+ * 2) A bunch of interrupts came in and moved
+ * the page forward again.
+ */
+ switch (ret) {
+ case RB_PAGE_HEAD:
+ case RB_PAGE_NORMAL:
+ /* OK */
+ break;
+ default:
+ RB_WARN_ON(cpu_buffer, 1);
+ return -1;
+ }
+
+ /*
+ * It is possible that an interrupt came in,
+ * set the head up, then more interrupts came in
+ * and moved it again. When we get back here,
+ * the page would have been set to NORMAL but we
+ * just set it back to HEAD.
+ *
+ * How do you detect this? Well, if that happened
+ * the tail page would have moved.
+ */
+ if (ret == RB_PAGE_NORMAL) {
+ /*
+ * If the tail had moved passed next, then we need
+ * to reset the pointer.
+ */
+ if (cpu_buffer->tail_page != tail_page &&
+ cpu_buffer->tail_page != next_page)
+ rb_head_page_set_normal(cpu_buffer, new_head,
+ next_page,
+ RB_PAGE_HEAD);
+ }
+
+ /*
+ * If this was the outer most commit (the one that
+ * changed the original pointer from HEAD to UPDATE),
+ * then it is up to us to reset it to NORMAL.
+ */
+ if (type == RB_PAGE_HEAD) {
+ ret = rb_head_page_set_normal(cpu_buffer, next_page,
+ tail_page,
+ RB_PAGE_UPDATE);
+ if (RB_WARN_ON(cpu_buffer,
+ ret != RB_PAGE_UPDATE))
+ return -1;
+ }
+
+ return 0;
+}
+
+static unsigned rb_calculate_event_length(unsigned length)
{
struct ring_buffer_event event; /* Used only for sizeof array */
return length;
}
-static struct ring_buffer_event *
-__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
- unsigned type, unsigned long length, u64 *ts)
+static inline void
+rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
+ struct buffer_page *tail_page,
+ unsigned long tail, unsigned long length)
{
- struct buffer_page *head_page, *tail_page;
- unsigned long tail;
- struct ring_buffer *buffer = cpu_buffer->buffer;
struct ring_buffer_event *event;
- tail_page = cpu_buffer->tail_page;
- head_page = cpu_buffer->head_page;
- tail = cpu_buffer->tail;
+ /*
+ * Only the event that crossed the page boundary
+ * must fill the old tail_page with padding.
+ */
+ if (tail >= BUF_PAGE_SIZE) {
+ local_sub(length, &tail_page->write);
+ return;
+ }
- if (tail + length > BUF_PAGE_SIZE) {
- struct buffer_page *next_page = tail_page;
+ event = __rb_page_index(tail_page, tail);
+ kmemcheck_annotate_bitfield(event, bitfield);
- rb_inc_page(cpu_buffer, &next_page);
+ /*
+ * If this event is bigger than the minimum size, then
+ * we need to be careful that we don't subtract the
+ * write counter enough to allow another writer to slip
+ * in on this page.
+ * We put in a discarded commit instead, to make sure
+ * that this space is not used again.
+ *
+ * If we are less than the minimum size, we don't need to
+ * worry about it.
+ */
+ if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) {
+ /* No room for any events */
- if (next_page == head_page) {
- if (!(buffer->flags & RB_FL_OVERWRITE))
- return NULL;
+ /* Mark the rest of the page with padding */
+ rb_event_set_padding(event);
+
+ /* Set the write back to the previous setting */
+ local_sub(length, &tail_page->write);
+ return;
+ }
- /* count overflows */
- rb_update_overflow(cpu_buffer);
+ /* Put in a discarded event */
+ event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE;
+ event->type_len = RINGBUF_TYPE_PADDING;
+ /* time delta must be non zero */
+ event->time_delta = 1;
- rb_inc_page(cpu_buffer, &head_page);
- cpu_buffer->head_page = head_page;
- rb_reset_read_page(cpu_buffer);
- }
+ /* Set write to end of buffer */
+ length = (tail + length) - BUF_PAGE_SIZE;
+ local_sub(length, &tail_page->write);
+}
+
+static struct ring_buffer_event *
+rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
+ unsigned long length, unsigned long tail,
+ struct buffer_page *commit_page,
+ struct buffer_page *tail_page, u64 *ts)
+{
+ struct ring_buffer *buffer = cpu_buffer->buffer;
+ struct buffer_page *next_page;
+ int ret;
+
+ next_page = tail_page;
+
+ rb_inc_page(cpu_buffer, &next_page);
+
+ /*
+ * If for some reason, we had an interrupt storm that made
+ * it all the way around the buffer, bail, and warn
+ * about it.
+ */
+ if (unlikely(next_page == commit_page)) {
+ local_inc(&cpu_buffer->commit_overrun);
+ goto out_reset;
+ }
+
+ /*
+ * This is where the fun begins!
+ *
+ * We are fighting against races between a reader that
+ * could be on another CPU trying to swap its reader
+ * page with the buffer head.
+ *
+ * We are also fighting against interrupts coming in and
+ * moving the head or tail on us as well.
+ *
+ * If the next page is the head page then we have filled
+ * the buffer, unless the commit page is still on the
+ * reader page.
+ */
+ if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) {
+
+ /*
+ * If the commit is not on the reader page, then
+ * move the header page.
+ */
+ if (!rb_is_reader_page(cpu_buffer->commit_page)) {
+ /*
+ * If we are not in overwrite mode,
+ * this is easy, just stop here.
+ */
+ if (!(buffer->flags & RB_FL_OVERWRITE))
+ goto out_reset;
- if (tail != BUF_PAGE_SIZE) {
- event = rb_page_index(tail_page, tail);
- /* page padding */
- event->type = RINGBUF_TYPE_PADDING;
+ ret = rb_handle_head_page(cpu_buffer,
+ tail_page,
+ next_page);
+ if (ret < 0)
+ goto out_reset;
+ if (ret)
+ goto out_again;
+ } else {
+ /*
+ * We need to be careful here too. The
+ * commit page could still be on the reader
+ * page. We could have a small buffer, and
+ * have filled up the buffer with events
+ * from interrupts and such, and wrapped.
+ *
+ * Note, if the tail page is also the on the
+ * reader_page, we let it move out.
+ */
+ if (unlikely((cpu_buffer->commit_page !=
+ cpu_buffer->tail_page) &&
+ (cpu_buffer->commit_page ==
+ cpu_buffer->reader_page))) {
+ local_inc(&cpu_buffer->commit_overrun);
+ goto out_reset;
+ }
}
+ }
- tail_page->size = tail;
- tail_page = next_page;
- tail_page->size = 0;
- tail = 0;
- cpu_buffer->tail_page = tail_page;
- cpu_buffer->tail = tail;
- rb_add_stamp(cpu_buffer, ts);
+ ret = rb_tail_page_update(cpu_buffer, tail_page, next_page);
+ if (ret) {
+ /*
+ * Nested commits always have zero deltas, so
+ * just reread the time stamp
+ */
+ *ts = rb_time_stamp(buffer, cpu_buffer->cpu);
+ next_page->page->time_stamp = *ts;
}
- BUG_ON(tail + length > BUF_PAGE_SIZE);
+ out_again:
+
+ rb_reset_tail(cpu_buffer, tail_page, tail, length);
+
+ /* fail and let the caller try again */
+ return ERR_PTR(-EAGAIN);
+
+ out_reset:
+ /* reset write */
+ rb_reset_tail(cpu_buffer, tail_page, tail, length);
- event = rb_page_index(tail_page, tail);
+ return NULL;
+}
+
+static struct ring_buffer_event *
+__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
+ unsigned type, unsigned long length, u64 *ts)
+{
+ struct buffer_page *tail_page, *commit_page;
+ struct ring_buffer_event *event;
+ unsigned long tail, write;
+
+ commit_page = cpu_buffer->commit_page;
+ /* we just need to protect against interrupts */
+ barrier();
+ tail_page = cpu_buffer->tail_page;
+ write = local_add_return(length, &tail_page->write);
+
+ /* set write to only the index of the write */
+ write &= RB_WRITE_MASK;
+ tail = write - length;
+
+ /* See if we shot pass the end of this buffer page */
+ if (write > BUF_PAGE_SIZE)
+ return rb_move_tail(cpu_buffer, length, tail,
+ commit_page, tail_page, ts);
+
+ /* We reserved something on the buffer */
+
+ event = __rb_page_index(tail_page, tail);
+ kmemcheck_annotate_bitfield(event, bitfield);
rb_update_event(event, type, length);
+ /* The passed in type is zero for DATA */
+ if (likely(!type))
+ local_inc(&tail_page->entries);
+
+ /*
+ * If this is the first commit on the page, then update
+ * its timestamp.
+ */
+ if (!tail)
+ tail_page->page->time_stamp = *ts;
+
return event;
}
+static inline int
+rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event)
+{
+ unsigned long new_index, old_index;
+ struct buffer_page *bpage;
+ unsigned long index;
+ unsigned long addr;
+
+ new_index = rb_event_index(event);
+ old_index = new_index + rb_event_length(event);
+ addr = (unsigned long)event;
+ addr &= PAGE_MASK;
+
+ bpage = cpu_buffer->tail_page;
+
+ if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
+ unsigned long write_mask =
+ local_read(&bpage->write) & ~RB_WRITE_MASK;
+ /*
+ * This is on the tail page. It is possible that
+ * a write could come in and move the tail page
+ * and write to the next page. That is fine
+ * because we just shorten what is on this page.
+ */
+ old_index += write_mask;
+ new_index += write_mask;
+ index = local_cmpxchg(&bpage->write, old_index, new_index);
+ if (index == old_index)
+ return 1;
+ }
+
+ /* could not discard */
+ return 0;
+}
+
static int
rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
u64 *ts, u64 *delta)
{
struct ring_buffer_event *event;
static int once;
+ int ret;
if (unlikely(*delta > (1ULL << 59) && !once++)) {
printk(KERN_WARNING "Delta way too big! %llu"
" ts=%llu write stamp = %llu\n",
- *delta, *ts, cpu_buffer->write_stamp);
+ (unsigned long long)*delta,
+ (unsigned long long)*ts,
+ (unsigned long long)cpu_buffer->write_stamp);
WARN_ON(1);
}
/*
- * The delta is too big, we to add a
- * new timestamp.
+ * The delta is too big, we to add a
+ * new timestamp.
+ */
+ event = __rb_reserve_next(cpu_buffer,
+ RINGBUF_TYPE_TIME_EXTEND,
+ RB_LEN_TIME_EXTEND,
+ ts);
+ if (!event)
+ return -EBUSY;
+
+ if (PTR_ERR(event) == -EAGAIN)
+ return -EAGAIN;
+
+ /* Only a commited time event can update the write stamp */
+ if (rb_event_is_commit(cpu_buffer, event)) {
+ /*
+ * If this is the first on the page, then it was
+ * updated with the page itself. Try to discard it
+ * and if we can't just make it zero.
+ */
+ if (rb_event_index(event)) {
+ event->time_delta = *delta & TS_MASK;
+ event->array[0] = *delta >> TS_SHIFT;
+ } else {
+ /* try to discard, since we do not need this */
+ if (!rb_try_to_discard(cpu_buffer, event)) {
+ /* nope, just zero it */
+ event->time_delta = 0;
+ event->array[0] = 0;
+ }
+ }
+ cpu_buffer->write_stamp = *ts;
+ /* let the caller know this was the commit */
+ ret = 1;
+ } else {
+ /* Try to discard the event */
+ if (!rb_try_to_discard(cpu_buffer, event)) {
+ /* Darn, this is just wasted space */
+ event->time_delta = 0;
+ event->array[0] = 0;
+ }
+ ret = 0;
+ }
+
+ *delta = 0;
+
+ return ret;
+}
+
+static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ local_inc(&cpu_buffer->committing);
+ local_inc(&cpu_buffer->commits);
+}
+
+static void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ unsigned long commits;
+
+ if (RB_WARN_ON(cpu_buffer,
+ !local_read(&cpu_buffer->committing)))
+ return;
+
+ again:
+ commits = local_read(&cpu_buffer->commits);
+ /* synchronize with interrupts */
+ barrier();
+ if (local_read(&cpu_buffer->committing) == 1)
+ rb_set_commit_to_write(cpu_buffer);
+
+ local_dec(&cpu_buffer->committing);
+
+ /* synchronize with interrupts */
+ barrier();
+
+ /*
+ * Need to account for interrupts coming in between the
+ * updating of the commit page and the clearing of the
+ * committing counter.
+ */
+ if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
+ !local_read(&cpu_buffer->committing)) {
+ local_inc(&cpu_buffer->committing);
+ goto again;
+ }
+}
+
+static struct ring_buffer_event *
+rb_reserve_next_event(struct ring_buffer *buffer,
+ struct ring_buffer_per_cpu *cpu_buffer,
+ unsigned long length)
+{
+ struct ring_buffer_event *event;
+ u64 ts, delta = 0;
+ int commit = 0;
+ int nr_loops = 0;
+
+ rb_start_commit(cpu_buffer);
+
+#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
+ /*
+ * Due to the ability to swap a cpu buffer from a buffer
+ * it is possible it was swapped before we committed.
+ * (committing stops a swap). We check for it here and
+ * if it happened, we have to fail the write.
+ */
+ barrier();
+ if (unlikely(ACCESS_ONCE(cpu_buffer->buffer) != buffer)) {
+ local_dec(&cpu_buffer->committing);
+ local_dec(&cpu_buffer->commits);
+ return NULL;
+ }
+#endif
+
+ length = rb_calculate_event_length(length);
+ again:
+ /*
+ * We allow for interrupts to reenter here and do a trace.
+ * If one does, it will cause this original code to loop
+ * back here. Even with heavy interrupts happening, this
+ * should only happen a few times in a row. If this happens
+ * 1000 times in a row, there must be either an interrupt
+ * storm or we have something buggy.
+ * Bail!
+ */
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
+ goto out_fail;
+
+ ts = rb_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu);
+
+ /*
+ * Only the first commit can update the timestamp.
+ * Yes there is a race here. If an interrupt comes in
+ * just after the conditional and it traces too, then it
+ * will also check the deltas. More than one timestamp may
+ * also be made. But only the entry that did the actual
+ * commit will be something other than zero.
*/
- event = __rb_reserve_next(cpu_buffer,
- RINGBUF_TYPE_TIME_EXTEND,
- RB_LEN_TIME_EXTEND,
- ts);
- if (!event)
- return -1;
+ if (likely(cpu_buffer->tail_page == cpu_buffer->commit_page &&
+ rb_page_write(cpu_buffer->tail_page) ==
+ rb_commit_index(cpu_buffer))) {
+ u64 diff;
- /* check to see if we went to the next page */
- if (cpu_buffer->tail) {
- /* Still on same page, update timestamp */
- event->time_delta = *delta & TS_MASK;
- event->array[0] = *delta >> TS_SHIFT;
- /* commit the time event */
- cpu_buffer->tail +=
- rb_event_length(event);
- cpu_buffer->write_stamp = *ts;
- *delta = 0;
- }
+ diff = ts - cpu_buffer->write_stamp;
- return 0;
-}
+ /* make sure this diff is calculated here */
+ barrier();
-static struct ring_buffer_event *
-rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
- unsigned type, unsigned long length)
-{
- struct ring_buffer_event *event;
- u64 ts, delta;
+ /* Did the write stamp get updated already? */
+ if (unlikely(ts < cpu_buffer->write_stamp))
+ goto get_event;
- ts = ring_buffer_time_stamp(cpu_buffer->cpu);
+ delta = diff;
+ if (unlikely(test_time_stamp(delta))) {
- if (cpu_buffer->tail) {
- delta = ts - cpu_buffer->write_stamp;
+ commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);
+ if (commit == -EBUSY)
+ goto out_fail;
- if (test_time_stamp(delta)) {
- int ret;
+ if (commit == -EAGAIN)
+ goto again;
- ret = rb_add_time_stamp(cpu_buffer, &ts, &delta);
- if (ret < 0)
- return NULL;
+ RB_WARN_ON(cpu_buffer, commit < 0);
}
- } else {
- rb_add_stamp(cpu_buffer, &ts);
- delta = 0;
}
- event = __rb_reserve_next(cpu_buffer, type, length, &ts);
+ get_event:
+ event = __rb_reserve_next(cpu_buffer, 0, length, &ts);
+ if (unlikely(PTR_ERR(event) == -EAGAIN))
+ goto again;
+
if (!event)
- return NULL;
+ goto out_fail;
- /* If the reserve went to the next page, our delta is zero */
- if (!cpu_buffer->tail)
+ if (!rb_event_is_commit(cpu_buffer, event))
delta = 0;
event->time_delta = delta;
return event;
+
+ out_fail:
+ rb_end_commit(cpu_buffer);
+ return NULL;
+}
+
+#ifdef CONFIG_TRACING
+
+#define TRACE_RECURSIVE_DEPTH 16
+
+static int trace_recursive_lock(void)
+{
+ current->trace_recursion++;
+
+ if (likely(current->trace_recursion < TRACE_RECURSIVE_DEPTH))
+ return 0;
+
+ /* Disable all tracing before we do anything else */
+ tracing_off_permanent();
+
+ printk_once(KERN_WARNING "Tracing recursion: depth[%ld]:"
+ "HC[%lu]:SC[%lu]:NMI[%lu]\n",
+ current->trace_recursion,
+ hardirq_count() >> HARDIRQ_SHIFT,
+ softirq_count() >> SOFTIRQ_SHIFT,
+ in_nmi());
+
+ WARN_ON_ONCE(1);
+ return -1;
+}
+
+static void trace_recursive_unlock(void)
+{
+ WARN_ON_ONCE(!current->trace_recursion);
+
+ current->trace_recursion--;
}
+#else
+
+#define trace_recursive_lock() (0)
+#define trace_recursive_unlock() do { } while (0)
+
+#endif
+
+static DEFINE_PER_CPU(int, rb_need_resched);
+
/**
* ring_buffer_lock_reserve - reserve a part of the buffer
* @buffer: the ring buffer to reserve from
* @length: the length of the data to reserve (excluding event header)
- * @flags: a pointer to save the interrupt flags
*
* Returns a reseverd event on the ring buffer to copy directly to.
* The user of this interface will need to get the body to write into
* If NULL is returned, then nothing has been allocated or locked.
*/
struct ring_buffer_event *
-ring_buffer_lock_reserve(struct ring_buffer *buffer,
- unsigned long length,
- unsigned long *flags)
+ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
- int cpu;
+ int cpu, resched;
+
+ if (ring_buffer_flags != RB_BUFFERS_ON)
+ return NULL;
if (atomic_read(&buffer->record_disabled))
return NULL;
- raw_local_irq_save(*flags);
+ /* If we are tracing schedule, we don't want to recurse */
+ resched = ftrace_preempt_disable();
+
+ if (trace_recursive_lock())
+ goto out_nocheck;
+
cpu = raw_smp_processor_id();
- if (!cpu_isset(cpu, buffer->cpumask))
- goto out_irq;
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ goto out;
cpu_buffer = buffer->buffers[cpu];
- spin_lock(&cpu_buffer->lock);
if (atomic_read(&cpu_buffer->record_disabled))
- goto no_record;
+ goto out;
- length = rb_calculate_event_length(length);
- if (length > BUF_PAGE_SIZE)
- return NULL;
+ if (length > BUF_MAX_DATA_SIZE)
+ goto out;
- event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, length);
+ event = rb_reserve_next_event(buffer, cpu_buffer, length);
if (!event)
- goto no_record;
+ goto out;
+
+ /*
+ * Need to store resched state on this cpu.
+ * Only the first needs to.
+ */
+
+ if (preempt_count() == 1)
+ per_cpu(rb_need_resched, cpu) = resched;
return event;
- no_record:
- spin_unlock(&cpu_buffer->lock);
- out_irq:
- local_irq_restore(*flags);
+ out:
+ trace_recursive_unlock();
+
+ out_nocheck:
+ ftrace_preempt_enable(resched);
return NULL;
}
+EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
+
+static void
+rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event)
+{
+ /*
+ * The event first in the commit queue updates the
+ * time stamp.
+ */
+ if (rb_event_is_commit(cpu_buffer, event))
+ cpu_buffer->write_stamp += event->time_delta;
+}
static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
- cpu_buffer->tail += rb_event_length(event);
- cpu_buffer->tail_page->size = cpu_buffer->tail;
- cpu_buffer->write_stamp += event->time_delta;
- cpu_buffer->entries++;
+ local_inc(&cpu_buffer->entries);
+ rb_update_write_stamp(cpu_buffer, event);
+ rb_end_commit(cpu_buffer);
}
/**
* ring_buffer_unlock_commit - commit a reserved
* @buffer: The buffer to commit to
* @event: The event pointer to commit.
- * @flags: the interrupt flags received from ring_buffer_lock_reserve.
*
* This commits the data to the ring buffer, and releases any locks held.
*
* Must be paired with ring_buffer_lock_reserve.
*/
int ring_buffer_unlock_commit(struct ring_buffer *buffer,
- struct ring_buffer_event *event,
- unsigned long flags)
+ struct ring_buffer_event *event)
{
struct ring_buffer_per_cpu *cpu_buffer;
int cpu = raw_smp_processor_id();
cpu_buffer = buffer->buffers[cpu];
- assert_spin_locked(&cpu_buffer->lock);
-
rb_commit(cpu_buffer, event);
- spin_unlock(&cpu_buffer->lock);
- raw_local_irq_restore(flags);
+ trace_recursive_unlock();
+
+ /*
+ * Only the last preempt count needs to restore preemption.
+ */
+ if (preempt_count() == 1)
+ ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
+ else
+ preempt_enable_no_resched_notrace();
return 0;
}
+EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
+
+static inline void rb_event_discard(struct ring_buffer_event *event)
+{
+ /* array[0] holds the actual length for the discarded event */
+ event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
+ event->type_len = RINGBUF_TYPE_PADDING;
+ /* time delta must be non zero */
+ if (!event->time_delta)
+ event->time_delta = 1;
+}
+
+/*
+ * Decrement the entries to the page that an event is on.
+ * The event does not even need to exist, only the pointer
+ * to the page it is on. This may only be called before the commit
+ * takes place.
+ */
+static inline void
+rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
+ struct ring_buffer_event *event)
+{
+ unsigned long addr = (unsigned long)event;
+ struct buffer_page *bpage = cpu_buffer->commit_page;
+ struct buffer_page *start;
+
+ addr &= PAGE_MASK;
+
+ /* Do the likely case first */
+ if (likely(bpage->page == (void *)addr)) {
+ local_dec(&bpage->entries);
+ return;
+ }
+
+ /*
+ * Because the commit page may be on the reader page we
+ * start with the next page and check the end loop there.
+ */
+ rb_inc_page(cpu_buffer, &bpage);
+ start = bpage;
+ do {
+ if (bpage->page == (void *)addr) {
+ local_dec(&bpage->entries);
+ return;
+ }
+ rb_inc_page(cpu_buffer, &bpage);
+ } while (bpage != start);
+
+ /* commit not part of this buffer?? */
+ RB_WARN_ON(cpu_buffer, 1);
+}
+
+/**
+ * ring_buffer_commit_discard - discard an event that has not been committed
+ * @buffer: the ring buffer
+ * @event: non committed event to discard
+ *
+ * Sometimes an event that is in the ring buffer needs to be ignored.
+ * This function lets the user discard an event in the ring buffer
+ * and then that event will not be read later.
+ *
+ * This function only works if it is called before the the item has been
+ * committed. It will try to free the event from the ring buffer
+ * if another event has not been added behind it.
+ *
+ * If another event has been added behind it, it will set the event
+ * up as discarded, and perform the commit.
+ *
+ * If this function is called, do not call ring_buffer_unlock_commit on
+ * the event.
+ */
+void ring_buffer_discard_commit(struct ring_buffer *buffer,
+ struct ring_buffer_event *event)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ int cpu;
+
+ /* The event is discarded regardless */
+ rb_event_discard(event);
+
+ cpu = smp_processor_id();
+ cpu_buffer = buffer->buffers[cpu];
+
+ /*
+ * This must only be called if the event has not been
+ * committed yet. Thus we can assume that preemption
+ * is still disabled.
+ */
+ RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
+
+ rb_decrement_entry(cpu_buffer, event);
+ if (rb_try_to_discard(cpu_buffer, event))
+ goto out;
+
+ /*
+ * The commit is still visible by the reader, so we
+ * must still update the timestamp.
+ */
+ rb_update_write_stamp(cpu_buffer, event);
+ out:
+ rb_end_commit(cpu_buffer);
+
+ trace_recursive_unlock();
+
+ /*
+ * Only the last preempt count needs to restore preemption.
+ */
+ if (preempt_count() == 1)
+ ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
+ else
+ preempt_enable_no_resched_notrace();
+
+}
+EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
/**
* ring_buffer_write - write data to the buffer without reserving
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
- unsigned long event_length, flags;
void *body;
int ret = -EBUSY;
- int cpu;
+ int cpu, resched;
+
+ if (ring_buffer_flags != RB_BUFFERS_ON)
+ return -EBUSY;
if (atomic_read(&buffer->record_disabled))
return -EBUSY;
- local_irq_save(flags);
+ resched = ftrace_preempt_disable();
+
cpu = raw_smp_processor_id();
- if (!cpu_isset(cpu, buffer->cpumask))
- goto out_irq;
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ goto out;
cpu_buffer = buffer->buffers[cpu];
- spin_lock(&cpu_buffer->lock);
if (atomic_read(&cpu_buffer->record_disabled))
goto out;
- event_length = rb_calculate_event_length(length);
- event = rb_reserve_next_event(cpu_buffer,
- RINGBUF_TYPE_DATA, event_length);
+ if (length > BUF_MAX_DATA_SIZE)
+ goto out;
+
+ event = rb_reserve_next_event(buffer, cpu_buffer, length);
if (!event)
goto out;
ret = 0;
out:
- spin_unlock(&cpu_buffer->lock);
- out_irq:
- local_irq_restore(flags);
+ ftrace_preempt_enable(resched);
return ret;
}
+EXPORT_SYMBOL_GPL(ring_buffer_write);
-/**
- * ring_buffer_lock - lock the ring buffer
- * @buffer: The ring buffer to lock
- * @flags: The place to store the interrupt flags
- *
- * This locks all the per CPU buffers.
- *
- * Must be unlocked by ring_buffer_unlock.
- */
-void ring_buffer_lock(struct ring_buffer *buffer, unsigned long *flags)
-{
- struct ring_buffer_per_cpu *cpu_buffer;
- int cpu;
-
- local_irq_save(*flags);
-
- for_each_buffer_cpu(buffer, cpu) {
- cpu_buffer = buffer->buffers[cpu];
- spin_lock(&cpu_buffer->lock);
- }
-}
-
-/**
- * ring_buffer_unlock - unlock a locked buffer
- * @buffer: The locked buffer to unlock
- * @flags: The interrupt flags received by ring_buffer_lock
- */
-void ring_buffer_unlock(struct ring_buffer *buffer, unsigned long flags)
+static int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
{
- struct ring_buffer_per_cpu *cpu_buffer;
- int cpu;
+ struct buffer_page *reader = cpu_buffer->reader_page;
+ struct buffer_page *head = rb_set_head_page(cpu_buffer);
+ struct buffer_page *commit = cpu_buffer->commit_page;
- for (cpu = buffer->cpus - 1; cpu >= 0; cpu--) {
- if (!cpu_isset(cpu, buffer->cpumask))
- continue;
- cpu_buffer = buffer->buffers[cpu];
- spin_unlock(&cpu_buffer->lock);
- }
+ /* In case of error, head will be NULL */
+ if (unlikely(!head))
+ return 1;
- local_irq_restore(flags);
+ return reader->read == rb_page_commit(reader) &&
+ (commit == reader ||
+ (commit == head &&
+ head->read == rb_page_commit(commit)));
}
/**
{
atomic_inc(&buffer->record_disabled);
}
+EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
/**
* ring_buffer_record_enable - enable writes to the buffer
{
atomic_dec(&buffer->record_disabled);
}
+EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
/**
* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
{
struct ring_buffer_per_cpu *cpu_buffer;
- if (!cpu_isset(cpu, buffer->cpumask))
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
return;
cpu_buffer = buffer->buffers[cpu];
atomic_inc(&cpu_buffer->record_disabled);
}
+EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
/**
* ring_buffer_record_enable_cpu - enable writes to the buffer
{
struct ring_buffer_per_cpu *cpu_buffer;
- if (!cpu_isset(cpu, buffer->cpumask))
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
return;
cpu_buffer = buffer->buffers[cpu];
atomic_dec(&cpu_buffer->record_disabled);
}
+EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
/**
* ring_buffer_entries_cpu - get the number of entries in a cpu buffer
unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long ret;
- if (!cpu_isset(cpu, buffer->cpumask))
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
- return cpu_buffer->entries;
+ ret = (local_read(&cpu_buffer->entries) - local_read(&cpu_buffer->overrun))
+ - cpu_buffer->read;
+
+ return ret;
}
+EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
/**
* ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long ret;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return 0;
+
+ cpu_buffer = buffer->buffers[cpu];
+ ret = local_read(&cpu_buffer->overrun);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
+
+/**
+ * ring_buffer_commit_overrun_cpu - get the number of overruns caused by commits
+ * @buffer: The ring buffer
+ * @cpu: The per CPU buffer to get the number of overruns from
+ */
+unsigned long
+ring_buffer_commit_overrun_cpu(struct ring_buffer *buffer, int cpu)
+{
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long ret;
- if (!cpu_isset(cpu, buffer->cpumask))
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
- return cpu_buffer->overrun;
+ ret = local_read(&cpu_buffer->commit_overrun);
+
+ return ret;
}
+EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
/**
* ring_buffer_entries - get the number of entries in a buffer
/* if you care about this being correct, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
- entries += cpu_buffer->entries;
+ entries += (local_read(&cpu_buffer->entries) -
+ local_read(&cpu_buffer->overrun)) - cpu_buffer->read;
}
return entries;
}
+EXPORT_SYMBOL_GPL(ring_buffer_entries);
/**
* ring_buffer_overrun_cpu - get the number of overruns in buffer
/* if you care about this being correct, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
- overruns += cpu_buffer->overrun;
+ overruns += local_read(&cpu_buffer->overrun);
}
return overruns;
}
+EXPORT_SYMBOL_GPL(ring_buffer_overruns);
+
+static void rb_iter_reset(struct ring_buffer_iter *iter)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+
+ /* Iterator usage is expected to have record disabled */
+ if (list_empty(&cpu_buffer->reader_page->list)) {
+ iter->head_page = rb_set_head_page(cpu_buffer);
+ if (unlikely(!iter->head_page))
+ return;
+ iter->head = iter->head_page->read;
+ } else {
+ iter->head_page = cpu_buffer->reader_page;
+ iter->head = cpu_buffer->reader_page->read;
+ }
+ if (iter->head)
+ iter->read_stamp = cpu_buffer->read_stamp;
+ else
+ iter->read_stamp = iter->head_page->page->time_stamp;
+}
/**
* ring_buffer_iter_reset - reset an iterator
*/
void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
{
- struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+ struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long flags;
+
+ if (!iter)
+ return;
+
+ cpu_buffer = iter->cpu_buffer;
- iter->head_page = cpu_buffer->head_page;
- iter->head = cpu_buffer->head;
- rb_reset_iter_read_page(iter);
+ spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+ rb_iter_reset(iter);
+ spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
}
+EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
/**
* ring_buffer_iter_empty - check if an iterator has no more to read
cpu_buffer = iter->cpu_buffer;
- return iter->head_page == cpu_buffer->tail_page &&
- iter->head == cpu_buffer->tail;
+ return iter->head_page == cpu_buffer->commit_page &&
+ iter->head == rb_commit_index(cpu_buffer);
}
+EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
static void
rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
{
u64 delta;
- switch (event->type) {
+ switch (event->type_len) {
case RINGBUF_TYPE_PADDING:
return;
{
u64 delta;
- switch (event->type) {
+ switch (event->type_len) {
case RINGBUF_TYPE_PADDING:
return;
return;
}
-static void rb_advance_head(struct ring_buffer_per_cpu *cpu_buffer)
+static struct buffer_page *
+rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
{
- struct ring_buffer_event *event;
- unsigned length;
+ struct buffer_page *reader = NULL;
+ unsigned long flags;
+ int nr_loops = 0;
+ int ret;
+ local_irq_save(flags);
+ __raw_spin_lock(&cpu_buffer->lock);
+
+ again:
/*
- * Check if we are at the end of the buffer.
+ * This should normally only loop twice. But because the
+ * start of the reader inserts an empty page, it causes
+ * a case where we will loop three times. There should be no
+ * reason to loop four times (that I know of).
*/
- if (cpu_buffer->head >= cpu_buffer->head_page->size) {
- BUG_ON(cpu_buffer->head_page == cpu_buffer->tail_page);
- rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
- rb_reset_read_page(cpu_buffer);
- return;
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
+ reader = NULL;
+ goto out;
}
- event = rb_head_event(cpu_buffer);
+ reader = cpu_buffer->reader_page;
- if (event->type == RINGBUF_TYPE_DATA)
- cpu_buffer->entries--;
+ /* If there's more to read, return this page */
+ if (cpu_buffer->reader_page->read < rb_page_size(reader))
+ goto out;
- length = rb_event_length(event);
+ /* Never should we have an index greater than the size */
+ if (RB_WARN_ON(cpu_buffer,
+ cpu_buffer->reader_page->read > rb_page_size(reader)))
+ goto out;
+
+ /* check if we caught up to the tail */
+ reader = NULL;
+ if (cpu_buffer->commit_page == cpu_buffer->reader_page)
+ goto out;
/*
- * This should not be called to advance the header if we are
- * at the tail of the buffer.
+ * Reset the reader page to size zero.
*/
- BUG_ON((cpu_buffer->head_page == cpu_buffer->tail_page) &&
- (cpu_buffer->head + length > cpu_buffer->tail));
+ local_set(&cpu_buffer->reader_page->write, 0);
+ local_set(&cpu_buffer->reader_page->entries, 0);
+ local_set(&cpu_buffer->reader_page->page->commit, 0);
- rb_update_read_stamp(cpu_buffer, event);
+ spin:
+ /*
+ * Splice the empty reader page into the list around the head.
+ */
+ reader = rb_set_head_page(cpu_buffer);
+ cpu_buffer->reader_page->list.next = reader->list.next;
+ cpu_buffer->reader_page->list.prev = reader->list.prev;
+
+ /*
+ * cpu_buffer->pages just needs to point to the buffer, it
+ * has no specific buffer page to point to. Lets move it out
+ * of our way so we don't accidently swap it.
+ */
+ cpu_buffer->pages = reader->list.prev;
+
+ /* The reader page will be pointing to the new head */
+ rb_set_list_to_head(cpu_buffer, &cpu_buffer->reader_page->list);
+
+ /*
+ * Here's the tricky part.
+ *
+ * We need to move the pointer past the header page.
+ * But we can only do that if a writer is not currently
+ * moving it. The page before the header page has the
+ * flag bit '1' set if it is pointing to the page we want.
+ * but if the writer is in the process of moving it
+ * than it will be '2' or already moved '0'.
+ */
+
+ ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
+
+ /*
+ * If we did not convert it, then we must try again.
+ */
+ if (!ret)
+ goto spin;
+
+ /*
+ * Yeah! We succeeded in replacing the page.
+ *
+ * Now make the new head point back to the reader page.
+ */
+ reader->list.next->prev = &cpu_buffer->reader_page->list;
+ rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
+
+ /* Finally update the reader page to the new head */
+ cpu_buffer->reader_page = reader;
+ rb_reset_reader_page(cpu_buffer);
+
+ goto again;
+
+ out:
+ __raw_spin_unlock(&cpu_buffer->lock);
+ local_irq_restore(flags);
+
+ return reader;
+}
+
+static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
+{
+ struct ring_buffer_event *event;
+ struct buffer_page *reader;
+ unsigned length;
+
+ reader = rb_get_reader_page(cpu_buffer);
+
+ /* This function should not be called when buffer is empty */
+ if (RB_WARN_ON(cpu_buffer, !reader))
+ return;
- cpu_buffer->head += length;
+ event = rb_reader_event(cpu_buffer);
- /* check for end of page */
- if ((cpu_buffer->head >= cpu_buffer->head_page->size) &&
- (cpu_buffer->head_page != cpu_buffer->tail_page))
- rb_advance_head(cpu_buffer);
+ if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
+ cpu_buffer->read++;
+
+ rb_update_read_stamp(cpu_buffer, event);
+
+ length = rb_event_length(event);
+ cpu_buffer->reader_page->read += length;
}
static void rb_advance_iter(struct ring_buffer_iter *iter)
/*
* Check if we are at the end of the buffer.
*/
- if (iter->head >= iter->head_page->size) {
- BUG_ON(iter->head_page == cpu_buffer->tail_page);
- rb_inc_page(cpu_buffer, &iter->head_page);
- rb_reset_iter_read_page(iter);
+ if (iter->head >= rb_page_size(iter->head_page)) {
+ /* discarded commits can make the page empty */
+ if (iter->head_page == cpu_buffer->commit_page)
+ return;
+ rb_inc_iter(iter);
return;
}
* This should not be called to advance the header if we are
* at the tail of the buffer.
*/
- BUG_ON((iter->head_page == cpu_buffer->tail_page) &&
- (iter->head + length > cpu_buffer->tail));
+ if (RB_WARN_ON(cpu_buffer,
+ (iter->head_page == cpu_buffer->commit_page) &&
+ (iter->head + length > rb_commit_index(cpu_buffer))))
+ return;
rb_update_iter_read_stamp(iter, event);
iter->head += length;
/* check for end of page padding */
- if ((iter->head >= iter->head_page->size) &&
- (iter->head_page != cpu_buffer->tail_page))
+ if ((iter->head >= rb_page_size(iter->head_page)) &&
+ (iter->head_page != cpu_buffer->commit_page))
rb_advance_iter(iter);
}
-/**
- * ring_buffer_peek - peek at the next event to be read
- * @buffer: The ring buffer to read
- * @cpu: The cpu to peak at
- * @ts: The timestamp counter of this event.
- *
- * This will return the event that will be read next, but does
- * not consume the data.
- */
-struct ring_buffer_event *
-ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
+static struct ring_buffer_event *
+rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts)
{
- struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
+ struct buffer_page *reader;
+ int nr_loops = 0;
- if (!cpu_isset(cpu, buffer->cpumask))
+ again:
+ /*
+ * We repeat when a timestamp is encountered. It is possible
+ * to get multiple timestamps from an interrupt entering just
+ * as one timestamp is about to be written, or from discarded
+ * commits. The most that we can have is the number on a single page.
+ */
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
return NULL;
- cpu_buffer = buffer->buffers[cpu];
-
- again:
- if (rb_per_cpu_empty(cpu_buffer))
+ reader = rb_get_reader_page(cpu_buffer);
+ if (!reader)
return NULL;
- event = rb_head_event(cpu_buffer);
+ event = rb_reader_event(cpu_buffer);
- switch (event->type) {
+ switch (event->type_len) {
case RINGBUF_TYPE_PADDING:
- rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
- rb_reset_read_page(cpu_buffer);
- goto again;
+ if (rb_null_event(event))
+ RB_WARN_ON(cpu_buffer, 1);
+ /*
+ * Because the writer could be discarding every
+ * event it creates (which would probably be bad)
+ * if we were to go back to "again" then we may never
+ * catch up, and will trigger the warn on, or lock
+ * the box. Return the padding, and we will release
+ * the current locks, and try again.
+ */
+ return event;
case RINGBUF_TYPE_TIME_EXTEND:
/* Internal data, OK to advance */
- rb_advance_head(cpu_buffer);
+ rb_advance_reader(cpu_buffer);
goto again;
case RINGBUF_TYPE_TIME_STAMP:
/* FIXME: not implemented */
- rb_advance_head(cpu_buffer);
+ rb_advance_reader(cpu_buffer);
goto again;
case RINGBUF_TYPE_DATA:
if (ts) {
*ts = cpu_buffer->read_stamp + event->time_delta;
- ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
+ ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
+ cpu_buffer->cpu, ts);
}
return event;
return NULL;
}
+EXPORT_SYMBOL_GPL(ring_buffer_peek);
-/**
- * ring_buffer_iter_peek - peek at the next event to be read
- * @iter: The ring buffer iterator
- * @ts: The timestamp counter of this event.
- *
- * This will return the event that will be read next, but does
- * not increment the iterator.
- */
-struct ring_buffer_event *
-ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
+static struct ring_buffer_event *
+rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
{
struct ring_buffer *buffer;
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
+ int nr_loops = 0;
if (ring_buffer_iter_empty(iter))
return NULL;
buffer = cpu_buffer->buffer;
again:
+ /*
+ * We repeat when a timestamp is encountered.
+ * We can get multiple timestamps by nested interrupts or also
+ * if filtering is on (discarding commits). Since discarding
+ * commits can be frequent we can get a lot of timestamps.
+ * But we limit them by not adding timestamps if they begin
+ * at the start of a page.
+ */
+ if (RB_WARN_ON(cpu_buffer, ++nr_loops > RB_TIMESTAMPS_PER_PAGE))
+ return NULL;
+
if (rb_per_cpu_empty(cpu_buffer))
return NULL;
event = rb_iter_head_event(iter);
- switch (event->type) {
+ switch (event->type_len) {
case RINGBUF_TYPE_PADDING:
- rb_inc_page(cpu_buffer, &iter->head_page);
- rb_reset_iter_read_page(iter);
- goto again;
+ if (rb_null_event(event)) {
+ rb_inc_iter(iter);
+ goto again;
+ }
+ rb_advance_iter(iter);
+ return event;
case RINGBUF_TYPE_TIME_EXTEND:
/* Internal data, OK to advance */
case RINGBUF_TYPE_DATA:
if (ts) {
*ts = iter->read_stamp + event->time_delta;
- ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
+ ring_buffer_normalize_time_stamp(buffer,
+ cpu_buffer->cpu, ts);
}
return event;
return NULL;
}
+EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
+
+static inline int rb_ok_to_lock(void)
+{
+ /*
+ * If an NMI die dumps out the content of the ring buffer
+ * do not grab locks. We also permanently disable the ring
+ * buffer too. A one time deal is all you get from reading
+ * the ring buffer from an NMI.
+ */
+ if (likely(!in_nmi()))
+ return 1;
+
+ tracing_off_permanent();
+ return 0;
+}
+
+/**
+ * ring_buffer_peek - peek at the next event to be read
+ * @buffer: The ring buffer to read
+ * @cpu: The cpu to peak at
+ * @ts: The timestamp counter of this event.
+ *
+ * This will return the event that will be read next, but does
+ * not consume the data.
+ */
+struct ring_buffer_event *
+ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
+ struct ring_buffer_event *event;
+ unsigned long flags;
+ int dolock;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return NULL;
+
+ dolock = rb_ok_to_lock();
+ again:
+ local_irq_save(flags);
+ if (dolock)
+ spin_lock(&cpu_buffer->reader_lock);
+ event = rb_buffer_peek(cpu_buffer, ts);
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
+ rb_advance_reader(cpu_buffer);
+ if (dolock)
+ spin_unlock(&cpu_buffer->reader_lock);
+ local_irq_restore(flags);
+
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
+ goto again;
+
+ return event;
+}
+
+/**
+ * ring_buffer_iter_peek - peek at the next event to be read
+ * @iter: The ring buffer iterator
+ * @ts: The timestamp counter of this event.
+ *
+ * This will return the event that will be read next, but does
+ * not increment the iterator.
+ */
+struct ring_buffer_event *
+ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+ struct ring_buffer_event *event;
+ unsigned long flags;
+
+ again:
+ spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+ event = rb_iter_peek(iter, ts);
+ spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
+ goto again;
+
+ return event;
+}
/**
* ring_buffer_consume - return an event and consume it
ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
{
struct ring_buffer_per_cpu *cpu_buffer;
- struct ring_buffer_event *event;
+ struct ring_buffer_event *event = NULL;
+ unsigned long flags;
+ int dolock;
- if (!cpu_isset(cpu, buffer->cpumask))
- return NULL;
+ dolock = rb_ok_to_lock();
- event = ring_buffer_peek(buffer, cpu, ts);
- if (!event)
- return NULL;
+ again:
+ /* might be called in atomic */
+ preempt_disable();
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ goto out;
cpu_buffer = buffer->buffers[cpu];
- rb_advance_head(cpu_buffer);
+ local_irq_save(flags);
+ if (dolock)
+ spin_lock(&cpu_buffer->reader_lock);
+
+ event = rb_buffer_peek(cpu_buffer, ts);
+ if (event)
+ rb_advance_reader(cpu_buffer);
+
+ if (dolock)
+ spin_unlock(&cpu_buffer->reader_lock);
+ local_irq_restore(flags);
+
+ out:
+ preempt_enable();
+
+ if (event && event->type_len == RINGBUF_TYPE_PADDING)
+ goto again;
return event;
}
+EXPORT_SYMBOL_GPL(ring_buffer_consume);
/**
* ring_buffer_read_start - start a non consuming read of the buffer
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_iter *iter;
+ unsigned long flags;
- if (!cpu_isset(cpu, buffer->cpumask))
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
return NULL;
iter = kmalloc(sizeof(*iter), GFP_KERNEL);
atomic_inc(&cpu_buffer->record_disabled);
synchronize_sched();
- spin_lock(&cpu_buffer->lock);
- iter->head = cpu_buffer->head;
- iter->head_page = cpu_buffer->head_page;
- rb_reset_iter_read_page(iter);
- spin_unlock(&cpu_buffer->lock);
+ spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+ __raw_spin_lock(&cpu_buffer->lock);
+ rb_iter_reset(iter);
+ __raw_spin_unlock(&cpu_buffer->lock);
+ spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
return iter;
}
+EXPORT_SYMBOL_GPL(ring_buffer_read_start);
/**
* ring_buffer_finish - finish reading the iterator of the buffer
atomic_dec(&cpu_buffer->record_disabled);
kfree(iter);
}
+EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
/**
* ring_buffer_read - read the next item in the ring buffer by the iterator
ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
{
struct ring_buffer_event *event;
+ struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+ unsigned long flags;
- event = ring_buffer_iter_peek(iter, ts);
+ spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+ again:
+ event = rb_iter_peek(iter, ts);
if (!event)
- return NULL;
+ goto out;
+
+ if (event->type_len == RINGBUF_TYPE_PADDING)
+ goto again;
rb_advance_iter(iter);
+ out:
+ spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
return event;
}
+EXPORT_SYMBOL_GPL(ring_buffer_read);
/**
* ring_buffer_size - return the size of the ring buffer (in bytes)
{
return BUF_PAGE_SIZE * buffer->pages;
}
+EXPORT_SYMBOL_GPL(ring_buffer_size);
static void
rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
{
+ rb_head_page_deactivate(cpu_buffer);
+
cpu_buffer->head_page
- = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
- cpu_buffer->tail_page
- = list_entry(cpu_buffer->pages.next, struct buffer_page, list);
+ = list_entry(cpu_buffer->pages, struct buffer_page, list);
+ local_set(&cpu_buffer->head_page->write, 0);
+ local_set(&cpu_buffer->head_page->entries, 0);
+ local_set(&cpu_buffer->head_page->page->commit, 0);
+
+ cpu_buffer->head_page->read = 0;
- cpu_buffer->head = cpu_buffer->tail = 0;
- cpu_buffer->overrun = 0;
- cpu_buffer->entries = 0;
+ cpu_buffer->tail_page = cpu_buffer->head_page;
+ cpu_buffer->commit_page = cpu_buffer->head_page;
+
+ INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
+ local_set(&cpu_buffer->reader_page->write, 0);
+ local_set(&cpu_buffer->reader_page->entries, 0);
+ local_set(&cpu_buffer->reader_page->page->commit, 0);
+ cpu_buffer->reader_page->read = 0;
+
+ local_set(&cpu_buffer->commit_overrun, 0);
+ local_set(&cpu_buffer->overrun, 0);
+ local_set(&cpu_buffer->entries, 0);
+ local_set(&cpu_buffer->committing, 0);
+ local_set(&cpu_buffer->commits, 0);
+ cpu_buffer->read = 0;
+
+ cpu_buffer->write_stamp = 0;
+ cpu_buffer->read_stamp = 0;
+
+ rb_head_page_activate(cpu_buffer);
}
/**
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
unsigned long flags;
- if (!cpu_isset(cpu, buffer->cpumask))
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
return;
- raw_local_irq_save(flags);
- spin_lock(&cpu_buffer->lock);
+ atomic_inc(&cpu_buffer->record_disabled);
+
+ spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+
+ if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
+ goto out;
+
+ __raw_spin_lock(&cpu_buffer->lock);
rb_reset_cpu(cpu_buffer);
- spin_unlock(&cpu_buffer->lock);
- raw_local_irq_restore(flags);
+ __raw_spin_unlock(&cpu_buffer->lock);
+
+ out:
+ spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+ atomic_dec(&cpu_buffer->record_disabled);
}
+EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
/**
* ring_buffer_reset - reset a ring buffer
*/
void ring_buffer_reset(struct ring_buffer *buffer)
{
- unsigned long flags;
int cpu;
- ring_buffer_lock(buffer, &flags);
-
for_each_buffer_cpu(buffer, cpu)
- rb_reset_cpu(buffer->buffers[cpu]);
-
- ring_buffer_unlock(buffer, flags);
+ ring_buffer_reset_cpu(buffer, cpu);
}
+EXPORT_SYMBOL_GPL(ring_buffer_reset);
/**
* rind_buffer_empty - is the ring buffer empty?
int ring_buffer_empty(struct ring_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long flags;
+ int dolock;
int cpu;
+ int ret;
+
+ dolock = rb_ok_to_lock();
/* yes this is racy, but if you don't like the race, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
- if (!rb_per_cpu_empty(cpu_buffer))
+ local_irq_save(flags);
+ if (dolock)
+ spin_lock(&cpu_buffer->reader_lock);
+ ret = rb_per_cpu_empty(cpu_buffer);
+ if (dolock)
+ spin_unlock(&cpu_buffer->reader_lock);
+ local_irq_restore(flags);
+
+ if (!ret)
return 0;
}
+
return 1;
}
+EXPORT_SYMBOL_GPL(ring_buffer_empty);
/**
* ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long flags;
+ int dolock;
+ int ret;
- if (!cpu_isset(cpu, buffer->cpumask))
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 1;
+ dolock = rb_ok_to_lock();
+
cpu_buffer = buffer->buffers[cpu];
- return rb_per_cpu_empty(cpu_buffer);
+ local_irq_save(flags);
+ if (dolock)
+ spin_lock(&cpu_buffer->reader_lock);
+ ret = rb_per_cpu_empty(cpu_buffer);
+ if (dolock)
+ spin_unlock(&cpu_buffer->reader_lock);
+ local_irq_restore(flags);
+
+ return ret;
}
+EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
+#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
/**
* ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
* @buffer_a: One buffer to swap with
{
struct ring_buffer_per_cpu *cpu_buffer_a;
struct ring_buffer_per_cpu *cpu_buffer_b;
+ int ret = -EINVAL;
- if (!cpu_isset(cpu, buffer_a->cpumask) ||
- !cpu_isset(cpu, buffer_b->cpumask))
- return -EINVAL;
+ if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
+ !cpumask_test_cpu(cpu, buffer_b->cpumask))
+ goto out;
/* At least make sure the two buffers are somewhat the same */
- if (buffer_a->size != buffer_b->size ||
- buffer_a->pages != buffer_b->pages)
- return -EINVAL;
+ if (buffer_a->pages != buffer_b->pages)
+ goto out;
+
+ ret = -EAGAIN;
+
+ if (ring_buffer_flags != RB_BUFFERS_ON)
+ goto out;
+
+ if (atomic_read(&buffer_a->record_disabled))
+ goto out;
+
+ if (atomic_read(&buffer_b->record_disabled))
+ goto out;
cpu_buffer_a = buffer_a->buffers[cpu];
cpu_buffer_b = buffer_b->buffers[cpu];
+ if (atomic_read(&cpu_buffer_a->record_disabled))
+ goto out;
+
+ if (atomic_read(&cpu_buffer_b->record_disabled))
+ goto out;
+
/*
* We can't do a synchronize_sched here because this
* function can be called in atomic context.
atomic_inc(&cpu_buffer_a->record_disabled);
atomic_inc(&cpu_buffer_b->record_disabled);
+ ret = -EBUSY;
+ if (local_read(&cpu_buffer_a->committing))
+ goto out_dec;
+ if (local_read(&cpu_buffer_b->committing))
+ goto out_dec;
+
buffer_a->buffers[cpu] = cpu_buffer_b;
buffer_b->buffers[cpu] = cpu_buffer_a;
cpu_buffer_b->buffer = buffer_a;
cpu_buffer_a->buffer = buffer_b;
+ ret = 0;
+
+out_dec:
atomic_dec(&cpu_buffer_a->record_disabled);
atomic_dec(&cpu_buffer_b->record_disabled);
+out:
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
+#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
+
+/**
+ * ring_buffer_alloc_read_page - allocate a page to read from buffer
+ * @buffer: the buffer to allocate for.
+ *
+ * This function is used in conjunction with ring_buffer_read_page.
+ * When reading a full page from the ring buffer, these functions
+ * can be used to speed up the process. The calling function should
+ * allocate a few pages first with this function. Then when it
+ * needs to get pages from the ring buffer, it passes the result
+ * of this function into ring_buffer_read_page, which will swap
+ * the page that was allocated, with the read page of the buffer.
+ *
+ * Returns:
+ * The page allocated, or NULL on error.
+ */
+void *ring_buffer_alloc_read_page(struct ring_buffer *buffer)
+{
+ struct buffer_data_page *bpage;
+ unsigned long addr;
+
+ addr = __get_free_page(GFP_KERNEL);
+ if (!addr)
+ return NULL;
+
+ bpage = (void *)addr;
+
+ rb_init_page(bpage);
+
+ return bpage;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
+
+/**
+ * ring_buffer_free_read_page - free an allocated read page
+ * @buffer: the buffer the page was allocate for
+ * @data: the page to free
+ *
+ * Free a page allocated from ring_buffer_alloc_read_page.
+ */
+void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
+{
+ free_page((unsigned long)data);
+}
+EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
+
+/**
+ * ring_buffer_read_page - extract a page from the ring buffer
+ * @buffer: buffer to extract from
+ * @data_page: the page to use allocated from ring_buffer_alloc_read_page
+ * @len: amount to extract
+ * @cpu: the cpu of the buffer to extract
+ * @full: should the extraction only happen when the page is full.
+ *
+ * This function will pull out a page from the ring buffer and consume it.
+ * @data_page must be the address of the variable that was returned
+ * from ring_buffer_alloc_read_page. This is because the page might be used
+ * to swap with a page in the ring buffer.
+ *
+ * for example:
+ * rpage = ring_buffer_alloc_read_page(buffer);
+ * if (!rpage)
+ * return error;
+ * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
+ * if (ret >= 0)
+ * process_page(rpage, ret);
+ *
+ * When @full is set, the function will not return true unless
+ * the writer is off the reader page.
+ *
+ * Note: it is up to the calling functions to handle sleeps and wakeups.
+ * The ring buffer can be used anywhere in the kernel and can not
+ * blindly call wake_up. The layer that uses the ring buffer must be
+ * responsible for that.
+ *
+ * Returns:
+ * >=0 if data has been transferred, returns the offset of consumed data.
+ * <0 if no data has been transferred.
+ */
+int ring_buffer_read_page(struct ring_buffer *buffer,
+ void **data_page, size_t len, int cpu, int full)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
+ struct ring_buffer_event *event;
+ struct buffer_data_page *bpage;
+ struct buffer_page *reader;
+ unsigned long flags;
+ unsigned int commit;
+ unsigned int read;
+ u64 save_timestamp;
+ int ret = -1;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ goto out;
+
+ /*
+ * If len is not big enough to hold the page header, then
+ * we can not copy anything.
+ */
+ if (len <= BUF_PAGE_HDR_SIZE)
+ goto out;
+
+ len -= BUF_PAGE_HDR_SIZE;
+
+ if (!data_page)
+ goto out;
+
+ bpage = *data_page;
+ if (!bpage)
+ goto out;
+
+ spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
+
+ reader = rb_get_reader_page(cpu_buffer);
+ if (!reader)
+ goto out_unlock;
+
+ event = rb_reader_event(cpu_buffer);
+
+ read = reader->read;
+ commit = rb_page_commit(reader);
+
+ /*
+ * If this page has been partially read or
+ * if len is not big enough to read the rest of the page or
+ * a writer is still on the page, then
+ * we must copy the data from the page to the buffer.
+ * Otherwise, we can simply swap the page with the one passed in.
+ */
+ if (read || (len < (commit - read)) ||
+ cpu_buffer->reader_page == cpu_buffer->commit_page) {
+ struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
+ unsigned int rpos = read;
+ unsigned int pos = 0;
+ unsigned int size;
+
+ if (full)
+ goto out_unlock;
+
+ if (len > (commit - read))
+ len = (commit - read);
+
+ size = rb_event_length(event);
+
+ if (len < size)
+ goto out_unlock;
+
+ /* save the current timestamp, since the user will need it */
+ save_timestamp = cpu_buffer->read_stamp;
+
+ /* Need to copy one event at a time */
+ do {
+ memcpy(bpage->data + pos, rpage->data + rpos, size);
+
+ len -= size;
+
+ rb_advance_reader(cpu_buffer);
+ rpos = reader->read;
+ pos += size;
+
+ event = rb_reader_event(cpu_buffer);
+ size = rb_event_length(event);
+ } while (len > size);
+
+ /* update bpage */
+ local_set(&bpage->commit, pos);
+ bpage->time_stamp = save_timestamp;
+
+ /* we copied everything to the beginning */
+ read = 0;
+ } else {
+ /* update the entry counter */
+ cpu_buffer->read += rb_page_entries(reader);
+
+ /* swap the pages */
+ rb_init_page(bpage);
+ bpage = reader->page;
+ reader->page = *data_page;
+ local_set(&reader->write, 0);
+ local_set(&reader->entries, 0);
+ reader->read = 0;
+ *data_page = bpage;
+ }
+ ret = read;
+
+ out_unlock:
+ spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+
+ out:
+ return ret;
+}
+EXPORT_SYMBOL_GPL(ring_buffer_read_page);
+
+#ifdef CONFIG_TRACING
+static ssize_t
+rb_simple_read(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ unsigned long *p = filp->private_data;
+ char buf[64];
+ int r;
+
+ if (test_bit(RB_BUFFERS_DISABLED_BIT, p))
+ r = sprintf(buf, "permanently disabled\n");
+ else
+ r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, p));
+
+ return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+static ssize_t
+rb_simple_write(struct file *filp, const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ unsigned long *p = filp->private_data;
+ char buf[64];
+ unsigned long val;
+ int ret;
+
+ if (cnt >= sizeof(buf))
+ return -EINVAL;
+
+ if (copy_from_user(&buf, ubuf, cnt))
+ return -EFAULT;
+
+ buf[cnt] = 0;
+
+ ret = strict_strtoul(buf, 10, &val);
+ if (ret < 0)
+ return ret;
+
+ if (val)
+ set_bit(RB_BUFFERS_ON_BIT, p);
+ else
+ clear_bit(RB_BUFFERS_ON_BIT, p);
+
+ (*ppos)++;
+
+ return cnt;
+}
+
+static const struct file_operations rb_simple_fops = {
+ .open = tracing_open_generic,
+ .read = rb_simple_read,
+ .write = rb_simple_write,
+};
+
+
+static __init int rb_init_debugfs(void)
+{
+ struct dentry *d_tracer;
+
+ d_tracer = tracing_init_dentry();
+
+ trace_create_file("tracing_on", 0644, d_tracer,
+ &ring_buffer_flags, &rb_simple_fops);
return 0;
}
+fs_initcall(rb_init_debugfs);
+#endif
+
+#ifdef CONFIG_HOTPLUG_CPU
+static int rb_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ struct ring_buffer *buffer =
+ container_of(self, struct ring_buffer, cpu_notify);
+ long cpu = (long)hcpu;
+
+ switch (action) {
+ case CPU_UP_PREPARE:
+ case CPU_UP_PREPARE_FROZEN:
+ if (cpumask_test_cpu(cpu, buffer->cpumask))
+ return NOTIFY_OK;
+
+ buffer->buffers[cpu] =
+ rb_allocate_cpu_buffer(buffer, cpu);
+ if (!buffer->buffers[cpu]) {
+ WARN(1, "failed to allocate ring buffer on CPU %ld\n",
+ cpu);
+ return NOTIFY_OK;
+ }
+ smp_wmb();
+ cpumask_set_cpu(cpu, buffer->cpumask);
+ break;
+ case CPU_DOWN_PREPARE:
+ case CPU_DOWN_PREPARE_FROZEN:
+ /*
+ * Do nothing.
+ * If we were to free the buffer, then the user would
+ * lose any trace that was in the buffer.
+ */
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+#endif
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff