Pileus Git - ~andy/linux/blob - kernel/trace/trace_event_profile.c

   1 /*
   2  * trace event based perf counter profiling
   3  *
   4  * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com>
   5  *
   6  */
   7
   8 #include <linux/module.h>
   9 #include "trace.h"
  10
  11 /*
  12  * We can't use a size but a type in alloc_percpu()
  13  * So let's create a dummy type that matches the desired size
  14  */
  15 typedef struct {char buf[FTRACE_MAX_PROFILE_SIZE];} profile_buf_t;
  16
  17 char            *trace_profile_buf;
  18 char            *trace_profile_buf_nmi;
  19
  20 /* Count the events in use (per event id, not per instance) */
  21 static int      total_profile_count;
  22
  23 static int ftrace_profile_enable_event(struct ftrace_event_call *event)
  24 {
  25         char *buf;
  26         int ret = -ENOMEM;
  27
  28         if (atomic_inc_return(&event->profile_count))
  29                 return 0;
  30
  31         if (!total_profile_count++) {
  32                 buf = (char *)alloc_percpu(profile_buf_t);
  33                 if (!buf)
  34                         goto fail_buf;
  35
  36                 rcu_assign_pointer(trace_profile_buf, buf);
  37
  38                 buf = (char *)alloc_percpu(profile_buf_t);
  39                 if (!buf)
  40                         goto fail_buf_nmi;
  41
  42                 rcu_assign_pointer(trace_profile_buf_nmi, buf);
  43         }
  44
  45         ret = event->profile_enable();
  46         if (!ret)
  47                 return 0;
  48
  49         kfree(trace_profile_buf_nmi);
  50 fail_buf_nmi:
  51         kfree(trace_profile_buf);
  52 fail_buf:
  53         total_profile_count--;
  54         atomic_dec(&event->profile_count);
  55
  56         return ret;
  57 }
  58
  59 int ftrace_profile_enable(int event_id)
  60 {
  61         struct ftrace_event_call *event;
  62         int ret = -EINVAL;
  63
  64         mutex_lock(&event_mutex);
  65         list_for_each_entry(event, &ftrace_events, list) {
  66                 if (event->id == event_id && event->profile_enable &&
  67                     try_module_get(event->mod)) {
  68                         ret = ftrace_profile_enable_event(event);
  69                         break;
  70                 }
  71         }
  72         mutex_unlock(&event_mutex);
  73
  74         return ret;
  75 }
  76
  77 static void ftrace_profile_disable_event(struct ftrace_event_call *event)
  78 {
  79         char *buf, *nmi_buf;
  80
  81         if (!atomic_add_negative(-1, &event->profile_count))
  82                 return;
  83
  84         event->profile_disable();
  85
  86         if (!--total_profile_count) {
  87                 buf = trace_profile_buf;
  88                 rcu_assign_pointer(trace_profile_buf, NULL);
  89
  90                 nmi_buf = trace_profile_buf_nmi;
  91                 rcu_assign_pointer(trace_profile_buf_nmi, NULL);
  92
  93                 /*
  94                  * Ensure every events in profiling have finished before
  95                  * releasing the buffers
  96                  */
  97                 synchronize_sched();
  98
  99                 free_percpu(buf);
 100                 free_percpu(nmi_buf);
 101         }
 102 }
 103
 104 void ftrace_profile_disable(int event_id)
 105 {
 106         struct ftrace_event_call *event;
 107
 108         mutex_lock(&event_mutex);
 109         list_for_each_entry(event, &ftrace_events, list) {
 110                 if (event->id == event_id) {
 111                         ftrace_profile_disable_event(event);
 112                         module_put(event->mod);
 113                         break;
 114                 }
 115         }
 116         mutex_unlock(&event_mutex);
 117 }