#include <linux/splice.h>
#include <linux/kdebug.h>
#include <linux/string.h>
+#include <linux/rwsem.h>
#include <linux/ctype.h>
#include <linux/init.h>
#include <linux/poll.h>
static cpumask_var_t __read_mostly tracing_buffer_mask;
-/* Define which cpu buffers are currently read in trace_pipe */
-static cpumask_var_t tracing_reader_cpumask;
-
#define for_each_tracing_cpu(cpu) \
for_each_cpu(cpu, tracing_buffer_mask)
/*
* trace_types_lock is used to protect the trace_types list.
- * This lock is also used to keep user access serialized.
- * Accesses from userspace will grab this lock while userspace
- * activities happen inside the kernel.
*/
static DEFINE_MUTEX(trace_types_lock);
+/*
+ * serialize the access of the ring buffer
+ *
+ * ring buffer serializes readers, but it is low level protection.
+ * The validity of the events (which returns by ring_buffer_peek() ..etc)
+ * are not protected by ring buffer.
+ *
+ * The content of events may become garbage if we allow other process consumes
+ * these events concurrently:
+ * A) the page of the consumed events may become a normal page
+ * (not reader page) in ring buffer, and this page will be rewrited
+ * by events producer.
+ * B) The page of the consumed events may become a page for splice_read,
+ * and this page will be returned to system.
+ *
+ * These primitives allow multi process access to different cpu ring buffer
+ * concurrently.
+ *
+ * These primitives don't distinguish read-only and read-consume access.
+ * Multi read-only access are also serialized.
+ */
+
+#ifdef CONFIG_SMP
+static DECLARE_RWSEM(all_cpu_access_lock);
+static DEFINE_PER_CPU(struct mutex, cpu_access_lock);
+
+static inline void trace_access_lock(int cpu)
+{
+ if (cpu == TRACE_PIPE_ALL_CPU) {
+ /* gain it for accessing the whole ring buffer. */
+ down_write(&all_cpu_access_lock);
+ } else {
+ /* gain it for accessing a cpu ring buffer. */
+
+ /* Firstly block other trace_access_lock(TRACE_PIPE_ALL_CPU). */
+ down_read(&all_cpu_access_lock);
+
+ /* Secondly block other access to this @cpu ring buffer. */
+ mutex_lock(&per_cpu(cpu_access_lock, cpu));
+ }
+}
+
+static inline void trace_access_unlock(int cpu)
+{
+ if (cpu == TRACE_PIPE_ALL_CPU) {
+ up_write(&all_cpu_access_lock);
+ } else {
+ mutex_unlock(&per_cpu(cpu_access_lock, cpu));
+ up_read(&all_cpu_access_lock);
+ }
+}
+
+static inline void trace_access_lock_init(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ mutex_init(&per_cpu(cpu_access_lock, cpu));
+}
+
+#else
+
+static DEFINE_MUTEX(access_lock);
+
+static inline void trace_access_lock(int cpu)
+{
+ (void)cpu;
+ mutex_lock(&access_lock);
+}
+
+static inline void trace_access_unlock(int cpu)
+{
+ (void)cpu;
+ mutex_unlock(&access_lock);
+}
+
+static inline void trace_access_lock_init(void)
+{
+}
+
+#endif
+
/* trace_wait is a waitqueue for tasks blocked on trace_poll */
static DECLARE_WAIT_QUEUE_HEAD(trace_wait);
entry->fmt = fmt;
memcpy(entry->buf, trace_buf, sizeof(u32) * len);
- if (!filter_check_discard(call, entry, buffer, event))
+ if (!filter_check_discard(call, entry, buffer, event)) {
ring_buffer_unlock_commit(buffer, event);
+ ftrace_trace_stack(buffer, flags, 6, pc);
+ }
out_unlock:
arch_spin_unlock(&trace_buf_lock);
memcpy(&entry->buf, trace_buf, len);
entry->buf[len] = '\0';
- if (!filter_check_discard(call, entry, buffer, event))
+ if (!filter_check_discard(call, entry, buffer, event)) {
ring_buffer_unlock_commit(buffer, event);
+ ftrace_trace_stack(buffer, irq_flags, 6, pc);
+ }
out_unlock:
arch_spin_unlock(&trace_buf_lock);
}
/*
- * No necessary locking here. The worst thing which can
- * happen is loosing events consumed at the same time
- * by a trace_pipe reader.
- * Other than that, we don't risk to crash the ring buffer
- * because it serializes the readers.
- *
* The current tracer is copied to avoid a global locking
* all around.
*/
}
trace_event_read_lock();
+ trace_access_lock(cpu_file);
return p;
}
static void s_stop(struct seq_file *m, void *p)
{
+ struct trace_iterator *iter = m->private;
+
atomic_dec(&trace_record_cmdline_disabled);
+ trace_access_unlock(iter->cpu_file);
trace_event_read_unlock();
}
mutex_lock(&trace_types_lock);
- /* We only allow one reader per cpu */
- if (cpu_file == TRACE_PIPE_ALL_CPU) {
- if (!cpumask_empty(tracing_reader_cpumask)) {
- ret = -EBUSY;
- goto out;
- }
- cpumask_setall(tracing_reader_cpumask);
- } else {
- if (!cpumask_test_cpu(cpu_file, tracing_reader_cpumask))
- cpumask_set_cpu(cpu_file, tracing_reader_cpumask);
- else {
- ret = -EBUSY;
- goto out;
- }
- }
-
/* create a buffer to store the information to pass to userspace */
iter = kzalloc(sizeof(*iter), GFP_KERNEL);
if (!iter) {
mutex_lock(&trace_types_lock);
- if (iter->cpu_file == TRACE_PIPE_ALL_CPU)
- cpumask_clear(tracing_reader_cpumask);
- else
- cpumask_clear_cpu(iter->cpu_file, tracing_reader_cpumask);
-
-
if (iter->trace->pipe_close)
iter->trace->pipe_close(iter);
iter->pos = -1;
trace_event_read_lock();
+ trace_access_lock(iter->cpu_file);
while (find_next_entry_inc(iter) != NULL) {
enum print_line_t ret;
int len = iter->seq.len;
if (iter->seq.len >= cnt)
break;
}
+ trace_access_unlock(iter->cpu_file);
trace_event_read_unlock();
/* Now copy what we have to the user */
}
trace_event_read_lock();
+ trace_access_lock(iter->cpu_file);
/* Fill as many pages as possible. */
for (i = 0, rem = len; i < PIPE_BUFFERS && rem; i++) {
trace_seq_init(&iter->seq);
}
+ trace_access_unlock(iter->cpu_file);
trace_event_read_unlock();
mutex_unlock(&iter->mutex);
info->read = 0;
+ trace_access_lock(info->cpu);
ret = ring_buffer_read_page(info->tr->buffer,
&info->spare,
count,
info->cpu, 0);
+ trace_access_unlock(info->cpu);
if (ret < 0)
return 0;
len &= PAGE_MASK;
}
+ trace_access_lock(info->cpu);
entries = ring_buffer_entries_cpu(info->tr->buffer, info->cpu);
for (i = 0; i < PIPE_BUFFERS && len && entries; i++, len -= PAGE_SIZE) {
entries = ring_buffer_entries_cpu(info->tr->buffer, info->cpu);
}
+ trace_access_unlock(info->cpu);
spd.nr_pages = i;
/* did we read anything? */
struct dentry *d_tracer;
int cpu;
+ trace_access_lock_init();
+
d_tracer = tracing_init_dentry();
trace_create_file("tracing_enabled", 0644, d_tracer,
if (!alloc_cpumask_var(&tracing_cpumask, GFP_KERNEL))
goto out_free_buffer_mask;
- if (!zalloc_cpumask_var(&tracing_reader_cpumask, GFP_KERNEL))
- goto out_free_tracing_cpumask;
-
/* To save memory, keep the ring buffer size to its minimum */
if (ring_buffer_expanded)
ring_buf_size = trace_buf_size;
return 0;
out_free_cpumask:
- free_cpumask_var(tracing_reader_cpumask);
-out_free_tracing_cpumask:
free_cpumask_var(tracing_cpumask);
out_free_buffer_mask:
free_cpumask_var(tracing_buffer_mask);
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff