![Linus Torvalds](/assets/img/avatar_default.png)
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
308 lines
6.5 KiB
C
308 lines
6.5 KiB
C
/**
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* @file cpu_buffer.c
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*
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* @remark Copyright 2002 OProfile authors
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* @remark Read the file COPYING
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*
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* @author John Levon <levon@movementarian.org>
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*
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* Each CPU has a local buffer that stores PC value/event
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* pairs. We also log context switches when we notice them.
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* Eventually each CPU's buffer is processed into the global
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* event buffer by sync_buffer().
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*
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* We use a local buffer for two reasons: an NMI or similar
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* interrupt cannot synchronise, and high sampling rates
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* would lead to catastrophic global synchronisation if
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* a global buffer was used.
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*/
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#include <linux/sched.h>
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#include <linux/oprofile.h>
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#include <linux/vmalloc.h>
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#include <linux/errno.h>
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#include "event_buffer.h"
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#include "cpu_buffer.h"
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#include "buffer_sync.h"
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#include "oprof.h"
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struct oprofile_cpu_buffer cpu_buffer[NR_CPUS] __cacheline_aligned;
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static void wq_sync_buffer(void *);
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#define DEFAULT_TIMER_EXPIRE (HZ / 10)
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static int work_enabled;
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void free_cpu_buffers(void)
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{
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int i;
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for_each_online_cpu(i) {
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vfree(cpu_buffer[i].buffer);
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}
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}
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int alloc_cpu_buffers(void)
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{
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int i;
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unsigned long buffer_size = fs_cpu_buffer_size;
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for_each_online_cpu(i) {
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struct oprofile_cpu_buffer * b = &cpu_buffer[i];
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b->buffer = vmalloc(sizeof(struct op_sample) * buffer_size);
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if (!b->buffer)
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goto fail;
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b->last_task = NULL;
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b->last_is_kernel = -1;
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b->tracing = 0;
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b->buffer_size = buffer_size;
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b->tail_pos = 0;
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b->head_pos = 0;
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b->sample_received = 0;
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b->sample_lost_overflow = 0;
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b->cpu = i;
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INIT_WORK(&b->work, wq_sync_buffer, b);
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}
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return 0;
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fail:
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free_cpu_buffers();
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return -ENOMEM;
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}
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void start_cpu_work(void)
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{
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int i;
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work_enabled = 1;
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for_each_online_cpu(i) {
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struct oprofile_cpu_buffer * b = &cpu_buffer[i];
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/*
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* Spread the work by 1 jiffy per cpu so they dont all
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* fire at once.
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*/
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schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i);
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}
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}
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void end_cpu_work(void)
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{
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int i;
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work_enabled = 0;
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for_each_online_cpu(i) {
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struct oprofile_cpu_buffer * b = &cpu_buffer[i];
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cancel_delayed_work(&b->work);
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}
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flush_scheduled_work();
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}
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/* Resets the cpu buffer to a sane state. */
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void cpu_buffer_reset(struct oprofile_cpu_buffer * cpu_buf)
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{
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/* reset these to invalid values; the next sample
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* collected will populate the buffer with proper
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* values to initialize the buffer
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*/
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cpu_buf->last_is_kernel = -1;
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cpu_buf->last_task = NULL;
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}
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/* compute number of available slots in cpu_buffer queue */
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static unsigned long nr_available_slots(struct oprofile_cpu_buffer const * b)
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{
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unsigned long head = b->head_pos;
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unsigned long tail = b->tail_pos;
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if (tail > head)
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return (tail - head) - 1;
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return tail + (b->buffer_size - head) - 1;
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}
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static void increment_head(struct oprofile_cpu_buffer * b)
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{
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unsigned long new_head = b->head_pos + 1;
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/* Ensure anything written to the slot before we
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* increment is visible */
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wmb();
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if (new_head < b->buffer_size)
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b->head_pos = new_head;
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else
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b->head_pos = 0;
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}
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inline static void
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add_sample(struct oprofile_cpu_buffer * cpu_buf,
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unsigned long pc, unsigned long event)
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{
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struct op_sample * entry = &cpu_buf->buffer[cpu_buf->head_pos];
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entry->eip = pc;
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entry->event = event;
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increment_head(cpu_buf);
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}
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inline static void
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add_code(struct oprofile_cpu_buffer * buffer, unsigned long value)
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{
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add_sample(buffer, ESCAPE_CODE, value);
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}
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/* This must be safe from any context. It's safe writing here
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* because of the head/tail separation of the writer and reader
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* of the CPU buffer.
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*
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* is_kernel is needed because on some architectures you cannot
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* tell if you are in kernel or user space simply by looking at
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* pc. We tag this in the buffer by generating kernel enter/exit
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* events whenever is_kernel changes
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*/
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static int log_sample(struct oprofile_cpu_buffer * cpu_buf, unsigned long pc,
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int is_kernel, unsigned long event)
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{
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struct task_struct * task;
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cpu_buf->sample_received++;
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if (nr_available_slots(cpu_buf) < 3) {
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cpu_buf->sample_lost_overflow++;
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return 0;
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}
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is_kernel = !!is_kernel;
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task = current;
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/* notice a switch from user->kernel or vice versa */
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if (cpu_buf->last_is_kernel != is_kernel) {
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cpu_buf->last_is_kernel = is_kernel;
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add_code(cpu_buf, is_kernel);
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}
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/* notice a task switch */
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if (cpu_buf->last_task != task) {
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cpu_buf->last_task = task;
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add_code(cpu_buf, (unsigned long)task);
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}
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add_sample(cpu_buf, pc, event);
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return 1;
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}
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static int oprofile_begin_trace(struct oprofile_cpu_buffer * cpu_buf)
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{
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if (nr_available_slots(cpu_buf) < 4) {
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cpu_buf->sample_lost_overflow++;
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return 0;
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}
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add_code(cpu_buf, CPU_TRACE_BEGIN);
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cpu_buf->tracing = 1;
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return 1;
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}
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static void oprofile_end_trace(struct oprofile_cpu_buffer * cpu_buf)
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{
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cpu_buf->tracing = 0;
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}
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void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
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{
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struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()];
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unsigned long pc = profile_pc(regs);
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int is_kernel = !user_mode(regs);
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if (!backtrace_depth) {
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log_sample(cpu_buf, pc, is_kernel, event);
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return;
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}
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if (!oprofile_begin_trace(cpu_buf))
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return;
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/* if log_sample() fail we can't backtrace since we lost the source
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* of this event */
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if (log_sample(cpu_buf, pc, is_kernel, event))
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oprofile_ops.backtrace(regs, backtrace_depth);
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oprofile_end_trace(cpu_buf);
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}
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void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event)
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{
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struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()];
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log_sample(cpu_buf, pc, is_kernel, event);
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}
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void oprofile_add_trace(unsigned long pc)
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{
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struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()];
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if (!cpu_buf->tracing)
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return;
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if (nr_available_slots(cpu_buf) < 1) {
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cpu_buf->tracing = 0;
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cpu_buf->sample_lost_overflow++;
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return;
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}
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/* broken frame can give an eip with the same value as an escape code,
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* abort the trace if we get it */
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if (pc == ESCAPE_CODE) {
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cpu_buf->tracing = 0;
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cpu_buf->backtrace_aborted++;
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return;
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}
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add_sample(cpu_buf, pc, 0);
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}
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/*
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* This serves to avoid cpu buffer overflow, and makes sure
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* the task mortuary progresses
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*
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* By using schedule_delayed_work_on and then schedule_delayed_work
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* we guarantee this will stay on the correct cpu
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*/
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static void wq_sync_buffer(void * data)
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{
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struct oprofile_cpu_buffer * b = data;
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if (b->cpu != smp_processor_id()) {
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printk("WQ on CPU%d, prefer CPU%d\n",
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smp_processor_id(), b->cpu);
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}
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sync_buffer(b->cpu);
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/* don't re-add the work if we're shutting down */
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if (work_enabled)
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schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
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}
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