gtk2_ardour/gprofhelper.c

   1 /* gprof-helper.c -- preload library to profile pthread-enabled programs
   2  *
   3  * Authors: Sam Hocevar <sam at zoy dot org>
   4  *          Daniel Jönsson <danieljo at fagotten dot org>
   5  *
   6  *  This program is free software; you can redistribute it and/or
   7  *  modify it under the terms of the Do What The Fuck You Want To
   8  *  Public License as published by Banlu Kemiyatorn. See
   9  *  http://sam.zoy.org/projects/COPYING.WTFPL for more details.
  10  *
  11  * Compilation example:
  12  * gcc -shared -nostdlib -fPIC gprof-helper.c -o gprof-helper.so -lpthread -ldl
  13  *
  14  * Usage example:
  15  * LD_PRELOAD=./gprof-helper.so your_program
  16  */
  17
  18 #define _GNU_SOURCE
  19 #include <sys/time.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <dlfcn.h>
  23 #include <pthread.h>
  24
  25 static void * wrapper_routine(void *);
  26
  27 /* Original pthread function */
  28 static int (*pthread_create_orig)(pthread_t *__restrict,
  29                                   __const pthread_attr_t *__restrict,
  30                                   void *(*)(void *),
  31                                   void *__restrict) = NULL;
  32
  33 /* Library initialization function */
  34 void _init(void)
  35 {
  36         pthread_create_orig = dlsym(RTLD_NEXT, "pthread_create");
  37         fprintf(stderr, "pthreads: using profiling hooks for gprof\n");
  38         if(pthread_create_orig == NULL)
  39         {
  40                 char *error = dlerror();
  41                 if(error == NULL)
  42                 {
  43                         error = "pthread_create is NULL";
  44                 }
  45                 fprintf(stderr, "%s", error);
  46                 exit(EXIT_FAILURE);
  47         }
  48 }
  49
  50 /* Our data structure passed to the wrapper */
  51 typedef struct wrapper_s
  52 {
  53         void * (*start_routine)(void *);
  54         void * arg;
  55
  56         pthread_mutex_t lock;
  57         pthread_cond_t  wait;
  58
  59         struct itimerval itimer;
  60
  61 } wrapper_t;
  62
  63 /* The wrapper function in charge for setting the itimer value */
  64 static void * wrapper_routine(void * data)
  65 {
  66         /* Put user data in thread-local variables */
  67         void * (*start_routine)(void *) = ((wrapper_t*)data)->start_routine;
  68         void * arg = ((wrapper_t*)data)->arg;
  69
  70         /* Set the profile timer value */
  71         setitimer(ITIMER_PROF, &((wrapper_t*)data)->itimer, NULL);
  72
  73         /* Tell the calling thread that we don't need its data anymore */
  74         pthread_mutex_lock(&((wrapper_t*)data)->lock);
  75         pthread_cond_signal(&((wrapper_t*)data)->wait);
  76         pthread_mutex_unlock(&((wrapper_t*)data)->lock);
  77
  78         /* Call the real function */
  79         return start_routine(arg);
  80 }
  81
  82 /* Our wrapper function for the real pthread_create() */
  83 int pthread_create(pthread_t *__restrict thread,
  84                    __const pthread_attr_t *__restrict attr,
  85                    void * (*start_routine)(void *),
  86                    void *__restrict arg)
  87 {
  88         wrapper_t wrapper_data;
  89         int i_return;
  90
  91         /* Initialize the wrapper structure */
  92         wrapper_data.start_routine = start_routine;
  93         wrapper_data.arg = arg;
  94         getitimer(ITIMER_PROF, &wrapper_data.itimer);
  95         pthread_cond_init(&wrapper_data.wait, NULL);
  96         pthread_mutex_init(&wrapper_data.lock, NULL);
  97         pthread_mutex_lock(&wrapper_data.lock);
  98
  99         /* The real pthread_create call */
 100         i_return = pthread_create_orig(thread,
 101                                    attr,
 102                                    &wrapper_routine,
 103                                    &wrapper_data);
 104
 105         /* If the thread was successfully spawned, wait for the data
 106          * to be released */
 107         if(i_return == 0)
 108         {
 109                 pthread_cond_wait(&wrapper_data.wait, &wrapper_data.lock);
 110         }
 111
 112         pthread_mutex_unlock(&wrapper_data.lock);
 113         pthread_mutex_destroy(&wrapper_data.lock);
 114         pthread_cond_destroy(&wrapper_data.wait);
 115
 116         return i_return;
 117 }