gdb/testsuite/gdb.threads/infcall-thread-announce.c

   1 /* This testcase is part of GDB, the GNU debugger.
   2
   3    Copyright 2023-2024 Free Software Foundation, Inc.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #include <assert.h>
  19 #include <pthread.h>
  20
  21 /* Test can create at most this number of extra threads.  */
  22 #define MAX_THREADS 3
  23
  24 /* For convenience.  */
  25 #define FALSE 0
  26 #define TRUE (!FALSE)
  27
  28 /* Controls a thread created by this test.  */
  29 struct thread_descriptor
  30 {
  31   /* The pthread handle.  Not valid unless STARTED is true.  */
  32   pthread_t thr;
  33
  34   /* This field is set to TRUE when a thread has been created, otherwise,
  35      is false.  */
  36   int started;
  37
  38   /* A condition variable and mutex, used for synchronising between the
  39      worker thread and the main thread.  */
  40   pthread_cond_t cond;
  41   pthread_mutex_t mutex;
  42 };
  43
  44 /* Keep track of worker threads.  */
  45 struct thread_descriptor threads[MAX_THREADS];
  46
  47 /* Worker thread function.  Doesn't do much.  Synchronise with the main
  48    thread, mark the thread as started, and then block waiting for the main
  49    thread.  Once the main thread wakes us, this thread exits.
  50
  51    ARG is a thread_descriptor shared with the main thread.  */
  52
  53 void *
  54 thread_function (void *arg)
  55 {
  56   int res;
  57   struct thread_descriptor *thread = (struct thread_descriptor *) arg;
  58
  59   /* Acquire the thread's lock.  Initially the main thread holds this lock,
  60      but releases it when the main thread enters a pthread_cond_wait.  */
  61   res = pthread_mutex_lock (&thread->mutex);
  62   assert (res == 0);
  63
  64   /* Mark the thread as started.  */
  65   thread->started = TRUE;
  66
  67   /* Signal the main thread to tell it we are started.  The main thread
  68      will still be blocked though as we hold the thread's lock.  */
  69   res = pthread_cond_signal (&thread->cond);
  70   assert (res == 0);
  71
  72   /* Now wait until the main thread tells us to exit.  By entering this
  73      pthread_cond_wait we release the lock, which allows the main thread to
  74      resume.  */
  75   res = pthread_cond_wait (&thread->cond, &thread->mutex);
  76   assert (res == 0);
  77
  78   /* The main thread woke us up.  We reacquired the thread lock as we left
  79      the pthread_cond_wait, so release the lock now.  */
  80   res = pthread_mutex_unlock (&thread->mutex);
  81   assert (res == 0);
  82
  83   return NULL;
  84 }
  85
  86 /* Start a new thread within the global THREADS array.  Return true if a
  87    new thread was started, otherwise return false.  */
  88
  89 int
  90 start_thread ()
  91 {
  92   int idx, res;
  93
  94   for (idx = 0; idx < MAX_THREADS; ++idx)
  95     if (!threads[idx].started)
  96       break;
  97
  98   if (idx == MAX_THREADS)
  99     return FALSE;
 100
 101   /* Acquire the thread lock before starting the new thread.  */
 102   res = pthread_mutex_lock (&threads[idx].mutex);
 103   assert (res == 0);
 104
 105   /* Start the new thread.  */
 106   res = pthread_create (&threads[idx].thr, NULL,
 107                         thread_function, &threads[idx]);
 108   assert (res == 0);
 109
 110   /* Unlock and wait.  The thread signals us once it is ready.  */
 111   res = pthread_cond_wait (&threads[idx].cond, &threads[idx].mutex);
 112   assert (res == 0);
 113
 114   /* The worker thread is now blocked in a pthread_cond_wait and we
 115      reacquired the lock as we left our own pthread_cond_wait above.  */
 116   res = pthread_mutex_unlock (&threads[idx].mutex);
 117   assert (res == 0);
 118
 119   return TRUE;
 120 }
 121
 122 /* Stop a thread from within the global THREADS array.  Return true if a
 123    thread was stopped, otherwise return false.  */
 124 int
 125 stop_thread ()
 126 {
 127   /* Look for a thread that is started.  */
 128   for (int idx = 0; idx < MAX_THREADS; ++idx)
 129     if (threads[idx].started)
 130       {
 131         int res;
 132
 133         /* Grab the thread lock.  */
 134         res = pthread_mutex_lock (&threads[idx].mutex);
 135         assert (res == 0);
 136
 137         /* Signal the worker thread, this wakes it up, but it can't exit
 138            until it acquires the thread lock, which we currently hold.  */
 139         res = pthread_cond_signal (&threads[idx].cond);
 140         assert (res == 0);
 141
 142         /* Release the thread lock, this allows the worker thread to exit.  */
 143         res = pthread_mutex_unlock (&threads[idx].mutex);
 144         assert (res == 0);
 145
 146         /* Now wait for the thread to exit.  */
 147         void *retval;
 148         res = pthread_join (threads[idx].thr, &retval);
 149         assert (res == 0);
 150         assert (retval == NULL);
 151
 152         /* Now the thread has exited, mark it as no longer started.  */
 153         assert (threads[idx].started);
 154         threads[idx].started = FALSE;
 155
 156         return TRUE;
 157       }
 158
 159   return FALSE;
 160 }
 161
 162 void
 163 init_descriptor_array ()
 164 {
 165   for (int i = 0; i < MAX_THREADS; ++i)
 166     {
 167       int res;
 168
 169       threads[i].started = FALSE;
 170       res = pthread_cond_init (&threads[i].cond, NULL);
 171       assert (res == 0);
 172       res = pthread_mutex_init (&threads[i].mutex, NULL);
 173       assert (res == 0);
 174     }
 175 }
 176
 177 void
 178 breakpt ()
 179 {
 180   /* Nothing.  */
 181 }
 182
 183 int
 184 main ()
 185 {
 186   init_descriptor_array ();
 187   breakpt ();
 188   start_thread ();
 189   stop_thread ();
 190   breakpt ();
 191   return 0;
 192 }