ceph/src/test/gprof-helper.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 -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 #include <sys/time.h>
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <dlfcn.h>
  22 #include <pthread.h>
  23
  24 static void * wrapper_routine(void *);
  25
  26 /* Original pthread function */
  27 static int (*pthread_create_orig)(pthread_t *__restrict,
  28                                   __const pthread_attr_t *__restrict,
  29                                   void *(*)(void *),
  30                                   void *__restrict) = NULL;
  31
  32 /* Library initialization function */
  33 void wooinit(void) __attribute__((constructor));
  34
  35 void wooinit(void)
  36 {
  37     pthread_create_orig = dlsym(RTLD_NEXT, "pthread_create");
  38     fprintf(stderr, "pthreads: using profiling hooks for gprof\n");
  39     if(pthread_create_orig == NULL)
  40     {
  41         char *error = dlerror();
  42         if(error == NULL)
  43         {
  44             error = "pthread_create is NULL";
  45         }
  46         fprintf(stderr, "%s\n", error);
  47         exit(EXIT_FAILURE);
  48     }
  49 }
  50
  51 /* Our data structure passed to the wrapper */
  52 typedef struct wrapper_s
  53 {
  54     void * (*start_routine)(void *);
  55     void * arg;
  56
  57     pthread_mutex_t lock;
  58     pthread_cond_t  wait;
  59
  60     struct itimerval itimer;
  61
  62 } wrapper_t;
  63
  64 /* The wrapper function in charge for setting the itimer value */
  65 static void * wrapper_routine(void * data)
  66 {
  67     /* Put user data in thread-local variables */
  68     void * (*start_routine)(void *) = ((wrapper_t*)data)->start_routine;
  69     void * arg = ((wrapper_t*)data)->arg;
  70
  71     /* Set the profile timer value */
  72     setitimer(ITIMER_PROF, &((wrapper_t*)data)->itimer, NULL);
  73
  74     /* Tell the calling thread that we don't need its data anymore */
  75     pthread_mutex_lock(&((wrapper_t*)data)->lock);
  76     pthread_cond_signal(&((wrapper_t*)data)->wait);
  77     pthread_mutex_unlock(&((wrapper_t*)data)->lock);
  78
  79     /* Call the real function */
  80     return start_routine(arg);
  81 }
  82
  83 /* Our wrapper function for the real pthread_create() */
  84 int pthread_create(pthread_t *__restrict thread,
  85                    __const pthread_attr_t *__restrict attr,
  86                    void * (*start_routine)(void *),
  87                    void *__restrict arg)
  88 {
  89     wrapper_t wrapper_data;
  90     int i_return;
  91
  92     /* Initialize the wrapper structure */
  93     wrapper_data.start_routine = start_routine;
  94     wrapper_data.arg = arg;
  95     getitimer(ITIMER_PROF, &wrapper_data.itimer);
  96     pthread_cond_init(&wrapper_data.wait, NULL);
  97     pthread_mutex_init(&wrapper_data.lock, NULL);
  98     pthread_mutex_lock(&wrapper_data.lock);
  99
 100     /* The real pthread_create call */
 101     i_return = pthread_create_orig(thread,
 102                                    attr,
 103                                    &wrapper_routine,
 104                                    &wrapper_data);
 105
 106     /* If the thread was successfully spawned, wait for the data
 107      * to be released */
 108     if(i_return == 0)
 109     {
 110         pthread_cond_wait(&wrapper_data.wait, &wrapper_data.lock);
 111     }
 112
 113     pthread_mutex_unlock(&wrapper_data.lock);
 114     pthread_mutex_destroy(&wrapper_data.lock);
 115     pthread_cond_destroy(&wrapper_data.wait);
 116
 117     return i_return;
 118 }
 119