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 char *perf_trace_buf;
  13 EXPORT_SYMBOL_GPL(perf_trace_buf);
  14
  15 char *perf_trace_buf_nmi;
  16 EXPORT_SYMBOL_GPL(perf_trace_buf_nmi);
  17
  18 typedef typeof(char [FTRACE_MAX_PROFILE_SIZE]) perf_trace_t ;
  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(perf_trace_t);
  33                 if (!buf)
  34                         goto fail_buf;
  35
  36                 rcu_assign_pointer(perf_trace_buf, buf);
  37
  38                 buf = (char *)alloc_percpu(perf_trace_t);
  39                 if (!buf)
  40                         goto fail_buf_nmi;
  41
  42                 rcu_assign_pointer(perf_trace_buf_nmi, buf);
  43         }
  44
  45         ret = event->profile_enable(event);
  46         if (!ret) {
  47                 total_profile_count++;
  48                 return 0;
  49         }
  50
  51 fail_buf_nmi:
  52         if (!total_profile_count) {
  53                 free_percpu(perf_trace_buf_nmi);
  54                 free_percpu(perf_trace_buf);
  55                 perf_trace_buf_nmi = NULL;
  56                 perf_trace_buf = NULL;
  57         }
  58 fail_buf:
  59         atomic_dec(&event->profile_count);
  60
  61         return ret;
  62 }
  63
  64 int ftrace_profile_enable(int event_id)
  65 {
  66         struct ftrace_event_call *event;
  67         int ret = -EINVAL;
  68
  69         mutex_lock(&event_mutex);
  70         list_for_each_entry(event, &ftrace_events, list) {
  71                 if (event->id == event_id && event->profile_enable &&
  72                     try_module_get(event->mod)) {
  73                         ret = ftrace_profile_enable_event(event);
  74                         break;
  75                 }
  76         }
  77         mutex_unlock(&event_mutex);
  78
  79         return ret;
  80 }
  81
  82 static void ftrace_profile_disable_event(struct ftrace_event_call *event)
  83 {
  84         char *buf, *nmi_buf;
  85
  86         if (!atomic_add_negative(-1, &event->profile_count))
  87                 return;
  88
  89         event->profile_disable(event);
  90
  91         if (!--total_profile_count) {
  92                 buf = perf_trace_buf;
  93                 rcu_assign_pointer(perf_trace_buf, NULL);
  94
  95                 nmi_buf = perf_trace_buf_nmi;
  96                 rcu_assign_pointer(perf_trace_buf_nmi, NULL);
  97
  98                 /*
  99                  * Ensure every events in profiling have finished before
 100                  * releasing the buffers
 101                  */
 102                 synchronize_sched();
 103
 104                 free_percpu(buf);
 105                 free_percpu(nmi_buf);
 106         }
 107 }
 108
 109 void ftrace_profile_disable(int event_id)
 110 {
 111         struct ftrace_event_call *event;
 112
 113         mutex_lock(&event_mutex);
 114         list_for_each_entry(event, &ftrace_events, list) {
 115                 if (event->id == event_id) {
 116                         ftrace_profile_disable_event(event);
 117                         module_put(event->mod);
 118                         break;
 119                 }
 120         }
 121         mutex_unlock(&event_mutex);
 122 }