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                 return 0;
  51
  52         kfree(trace_profile_buf_nmi);
  53 fail_buf_nmi:
  54         kfree(trace_profile_buf);
  55 fail_buf:
  56         total_profile_count--;
  57         atomic_dec(&event->profile_count);
  58
  59         return ret;
  60 }
  61
  62 int ftrace_profile_enable(int event_id)
  63 {
  64         struct ftrace_event_call *event;
  65         int ret = -EINVAL;
  66
  67         mutex_lock(&event_mutex);
  68         list_for_each_entry(event, &ftrace_events, list) {
  69                 if (event->id == event_id && event->profile_enable &&
  70                     try_module_get(event->mod)) {
  71                         ret = ftrace_profile_enable_event(event);
  72                         break;
  73                 }
  74         }
  75         mutex_unlock(&event_mutex);
  76
  77         return ret;
  78 }
  79
  80 static void ftrace_profile_disable_event(struct ftrace_event_call *event)
  81 {
  82         char *buf, *nmi_buf;
  83
  84         if (!atomic_add_negative(-1, &event->profile_count))
  85                 return;
  86
  87         event->profile_disable();
  88
  89         if (!--total_profile_count) {
  90                 buf = trace_profile_buf;
  91                 rcu_assign_pointer(trace_profile_buf, NULL);
  92
  93                 nmi_buf = trace_profile_buf_nmi;
  94                 rcu_assign_pointer(trace_profile_buf_nmi, NULL);
  95
  96                 /*
  97                  * Ensure every events in profiling have finished before
  98                  * releasing the buffers
  99                  */
 100                 synchronize_sched();
 101
 102                 free_percpu(buf);
 103                 free_percpu(nmi_buf);
 104         }
 105 }
 106
 107 void ftrace_profile_disable(int event_id)
 108 {
 109         struct ftrace_event_call *event;
 110
 111         mutex_lock(&event_mutex);
 112         list_for_each_entry(event, &ftrace_events, list) {
 113                 if (event->id == event_id) {
 114                         ftrace_profile_disable_event(event);
 115                         module_put(event->mod);
 116                         break;
 117                 }
 118         }
 119         mutex_unlock(&event_mutex);
 120 }