/** * @file cpu_buffer.c * * @remark Copyright 2002 OProfile authors * @remark Read the file COPYING * * @author John Levon * @author Barry Kasindorf * * Each CPU has a local buffer that stores PC value/event * pairs. We also log context switches when we notice them. * Eventually each CPU's buffer is processed into the global * event buffer by sync_buffer(). * * We use a local buffer for two reasons: an NMI or similar * interrupt cannot synchronise, and high sampling rates * would lead to catastrophic global synchronisation if * a global buffer was used. */ #include #include #include #include #include "event_buffer.h" #include "cpu_buffer.h" #include "buffer_sync.h" #include "oprof.h" #define OP_BUFFER_FLAGS 0 /* * Read and write access is using spin locking. Thus, writing to the * buffer by NMI handler (x86) could occur also during critical * sections when reading the buffer. To avoid this, there are 2 * buffers for independent read and write access. Read access is in * process context only, write access only in the NMI handler. If the * read buffer runs empty, both buffers are swapped atomically. There * is potentially a small window during swapping where the buffers are * disabled and samples could be lost. * * Using 2 buffers is a little bit overhead, but the solution is clear * and does not require changes in the ring buffer implementation. It * can be changed to a single buffer solution when the ring buffer * access is implemented as non-locking atomic code. */ static struct ring_buffer *op_ring_buffer_read; static struct ring_buffer *op_ring_buffer_write; DEFINE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer); static void wq_sync_buffer(struct work_struct *work); #define DEFAULT_TIMER_EXPIRE (HZ / 10) static int work_enabled; unsigned long oprofile_get_cpu_buffer_size(void) { return oprofile_cpu_buffer_size; } void oprofile_cpu_buffer_inc_smpl_lost(void) { struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer); cpu_buf->sample_lost_overflow++; } void free_cpu_buffers(void) { if (op_ring_buffer_read) ring_buffer_free(op_ring_buffer_read); op_ring_buffer_read = NULL; if (op_ring_buffer_write) ring_buffer_free(op_ring_buffer_write); op_ring_buffer_write = NULL; } int alloc_cpu_buffers(void) { int i; unsigned long buffer_size = oprofile_cpu_buffer_size; op_ring_buffer_read = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS); if (!op_ring_buffer_read) goto fail; op_ring_buffer_write = ring_buffer_alloc(buffer_size, OP_BUFFER_FLAGS); if (!op_ring_buffer_write) goto fail; for_each_possible_cpu(i) { struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i); b->last_task = NULL; b->last_is_kernel = -1; b->tracing = 0; b->buffer_size = buffer_size; b->tail_pos = 0; b->head_pos = 0; b->sample_received = 0; b->sample_lost_overflow = 0; b->backtrace_aborted = 0; b->sample_invalid_eip = 0; b->cpu = i; INIT_DELAYED_WORK(&b->work, wq_sync_buffer); } return 0; fail: free_cpu_buffers(); return -ENOMEM; } void start_cpu_work(void) { int i; work_enabled = 1; for_each_online_cpu(i) { struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i); /* * Spread the work by 1 jiffy per cpu so they dont all * fire at once. */ schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i); } } void end_cpu_work(void) { int i; work_enabled = 0; for_each_online_cpu(i) { struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i); cancel_delayed_work(&b->work); } flush_scheduled_work(); } int op_cpu_buffer_write_entry(struct op_entry *entry) { entry->event = ring_buffer_lock_reserve(op_ring_buffer_write, sizeof(struct op_sample), &entry->irq_flags); if (entry->event) entry->sample = ring_buffer_event_data(entry->event); else entry->sample = NULL; if (!entry->sample) return -ENOMEM; return 0; } int op_cpu_buffer_write_commit(struct op_entry *entry) { return ring_buffer_unlock_commit(op_ring_buffer_write, entry->event, entry->irq_flags); } struct op_sample *op_cpu_buffer_read_entry(int cpu) { struct ring_buffer_event *e; e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL); if (e) return ring_buffer_event_data(e); if (ring_buffer_swap_cpu(op_ring_buffer_read, op_ring_buffer_write, cpu)) return NULL; e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL); if (e) return ring_buffer_event_data(e); return NULL; } unsigned long op_cpu_buffer_entries(int cpu) { return ring_buffer_entries_cpu(op_ring_buffer_read, cpu) + ring_buffer_entries_cpu(op_ring_buffer_write, cpu); } static inline int add_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc, unsigned long event) { struct op_entry entry; int ret; ret = op_cpu_buffer_write_entry(&entry); if (ret) return ret; entry.sample->eip = pc; entry.sample->event = event; ret = op_cpu_buffer_write_commit(&entry); if (ret) return ret; return 0; } static inline int add_code(struct oprofile_cpu_buffer *buffer, unsigned long value) { return add_sample(buffer, ESCAPE_CODE, value); } /* This must be safe from any context. It's safe writing here * because of the head/tail separation of the writer and reader * of the CPU buffer. * * is_kernel is needed because on some architectures you cannot * tell if you are in kernel or user space simply by looking at * pc. We tag this in the buffer by generating kernel enter/exit * events whenever is_kernel changes */ static int log_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc, int is_kernel, unsigned long event) { struct task_struct *task; cpu_buf->sample_received++; if (pc == ESCAPE_CODE) { cpu_buf->sample_invalid_eip++; return 0; } is_kernel = !!is_kernel; task = current; /* notice a switch from user->kernel or vice versa */ if (cpu_buf->last_is_kernel != is_kernel) { cpu_buf->last_is_kernel = is_kernel; if (add_code(cpu_buf, is_kernel)) goto fail; } /* notice a task switch */ if (cpu_buf->last_task != task) { cpu_buf->last_task = task; if (add_code(cpu_buf, (unsigned long)task)) goto fail; } if (add_sample(cpu_buf, pc, event)) goto fail; return 1; fail: cpu_buf->sample_lost_overflow++; return 0; } static int oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf) { add_code(cpu_buf, CPU_TRACE_BEGIN); cpu_buf->tracing = 1; return 1; } static void oprofile_end_trace(struct oprofile_cpu_buffer *cpu_buf) { cpu_buf->tracing = 0; } static inline void __oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs, unsigned long event, int is_kernel) { struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer); if (!oprofile_backtrace_depth) { log_sample(cpu_buf, pc, is_kernel, event); return; } if (!oprofile_begin_trace(cpu_buf)) return; /* * if log_sample() fail we can't backtrace since we lost the * source of this event */ if (log_sample(cpu_buf, pc, is_kernel, event)) oprofile_ops.backtrace(regs, oprofile_backtrace_depth); oprofile_end_trace(cpu_buf); } void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs, unsigned long event, int is_kernel) { __oprofile_add_ext_sample(pc, regs, event, is_kernel); } void oprofile_add_sample(struct pt_regs * const regs, unsigned long event) { int is_kernel = !user_mode(regs); unsigned long pc = profile_pc(regs); __oprofile_add_ext_sample(pc, regs, event, is_kernel); } #ifdef CONFIG_OPROFILE_IBS #define MAX_IBS_SAMPLE_SIZE 14 void oprofile_add_ibs_sample(struct pt_regs * const regs, unsigned int * const ibs_sample, int ibs_code) { int is_kernel = !user_mode(regs); struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer); struct task_struct *task; int fail = 0; cpu_buf->sample_received++; /* notice a switch from user->kernel or vice versa */ if (cpu_buf->last_is_kernel != is_kernel) { if (add_code(cpu_buf, is_kernel)) goto fail; cpu_buf->last_is_kernel = is_kernel; } /* notice a task switch */ if (!is_kernel) { task = current; if (cpu_buf->last_task != task) { if (add_code(cpu_buf, (unsigned long)task)) goto fail; cpu_buf->last_task = task; } } fail = fail || add_code(cpu_buf, ibs_code); fail = fail || add_sample(cpu_buf, ibs_sample[0], ibs_sample[1]); fail = fail || add_sample(cpu_buf, ibs_sample[2], ibs_sample[3]); fail = fail || add_sample(cpu_buf, ibs_sample[4], ibs_sample[5]); if (ibs_code == IBS_OP_BEGIN) { fail = fail || add_sample(cpu_buf, ibs_sample[6], ibs_sample[7]); fail = fail || add_sample(cpu_buf, ibs_sample[8], ibs_sample[9]); fail = fail || add_sample(cpu_buf, ibs_sample[10], ibs_sample[11]); } if (fail) goto fail; if (oprofile_backtrace_depth) oprofile_ops.backtrace(regs, oprofile_backtrace_depth); return; fail: cpu_buf->sample_lost_overflow++; return; } #endif void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event) { struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer); log_sample(cpu_buf, pc, is_kernel, event); } void oprofile_add_trace(unsigned long pc) { struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer); if (!cpu_buf->tracing) return; /* * broken frame can give an eip with the same value as an * escape code, abort the trace if we get it */ if (pc == ESCAPE_CODE) goto fail; if (add_sample(cpu_buf, pc, 0)) goto fail; return; fail: cpu_buf->tracing = 0; cpu_buf->backtrace_aborted++; return; } /* * This serves to avoid cpu buffer overflow, and makes sure * the task mortuary progresses * * By using schedule_delayed_work_on and then schedule_delayed_work * we guarantee this will stay on the correct cpu */ static void wq_sync_buffer(struct work_struct *work) { struct oprofile_cpu_buffer *b = container_of(work, struct oprofile_cpu_buffer, work.work); if (b->cpu != smp_processor_id()) { printk(KERN_DEBUG "WQ on CPU%d, prefer CPU%d\n", smp_processor_id(), b->cpu); if (!cpu_online(b->cpu)) { cancel_delayed_work(&b->work); return; } } sync_buffer(b->cpu); /* don't re-add the work if we're shutting down */ if (work_enabled) schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE); }