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 EXPORT_SYMBOL_GPL(trace_profile_buf);
  19
  20 char            *trace_profile_buf_nmi;
  21 EXPORT_SYMBOL_GPL(trace_profile_buf_nmi);
  22
  23 /* Count the events in use (per event id, not per instance) */
  24 static int      total_profile_count;
  25
  26 static int ftrace_profile_enable_event(struct ftrace_event_call *event)
  27 {
  28         char *buf;
  29         int ret = -ENOMEM;
  30
  31         if (atomic_inc_return(&event->profile_count))
  32                 return 0;
  33
  34         if (!total_profile_count) {
  35                 buf = (char *)alloc_percpu(profile_buf_t);
  36                 if (!buf)
  37                         goto fail_buf;
  38
  39                 rcu_assign_pointer(trace_profile_buf, buf);
  40
  41                 buf = (char *)alloc_percpu(profile_buf_t);
  42                 if (!buf)
  43                         goto fail_buf_nmi;
  44
  45                 rcu_assign_pointer(trace_profile_buf_nmi, buf);
  46         }
  47
  48         ret = event->profile_enable();
  49         if (!ret) {
  50                 total_profile_count++;
  51                 return 0;
  52         }
  53
  54 fail_buf_nmi:
  55         if (!total_profile_count) {
  56                 free_percpu(trace_profile_buf_nmi);
  57                 free_percpu(trace_profile_buf);
  58                 trace_profile_buf_nmi = NULL;
  59                 trace_profile_buf = NULL;
  60         }
  61 fail_buf:
  62         atomic_dec(&event->profile_count);
  63
  64         return ret;
  65 }
  66
  67 int ftrace_profile_enable(int event_id)
  68 {
  69         struct ftrace_event_call *event;
  70         int ret = -EINVAL;
  71
  72         mutex_lock(&event_mutex);
  73         list_for_each_entry(event, &ftrace_events, list) {
  74                 if (event->id == event_id && event->profile_enable &&
  75                     try_module_get(event->mod)) {
  76                         ret = ftrace_profile_enable_event(event);
  77                         break;
  78                 }
  79         }
  80         mutex_unlock(&event_mutex);
  81
  82         return ret;
  83 }
  84
  85 static void ftrace_profile_disable_event(struct ftrace_event_call *event)
  86 {
  87         char *buf, *nmi_buf;
  88
  89         if (!atomic_add_negative(-1, &event->profile_count))
  90                 return;
  91
  92         event->profile_disable();
  93
  94         if (!--total_profile_count) {
  95                 buf = trace_profile_buf;
  96                 rcu_assign_pointer(trace_profile_buf, NULL);
  97
  98                 nmi_buf = trace_profile_buf_nmi;
  99                 rcu_assign_pointer(trace_profile_buf_nmi, NULL);
 100
 101                 /*
 102                  * Ensure every events in profiling have finished before
 103                  * releasing the buffers
 104                  */
 105                 synchronize_sched();
 106
 107                 free_percpu(buf);
 108                 free_percpu(nmi_buf);
 109         }
 110 }
 111
 112 void ftrace_profile_disable(int event_id)
 113 {
 114         struct ftrace_event_call *event;
 115
 116         mutex_lock(&event_mutex);
 117         list_for_each_entry(event, &ftrace_events, list) {
 118                 if (event->id == event_id) {
 119                         ftrace_profile_disable_event(event);
 120                         module_put(event->mod);
 121                         break;
 122                 }
 123         }
 124         mutex_unlock(&event_mutex);
 125 }