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 }