Fixed a race condition in msg for communication between two processes. The

[simgrid.git] / src / msg / msg_mailbox.c

diff --git a/src/msg/msg_mailbox.c b/src/msg/msg_mailbox.c
index 5a12459..a6a4444 100644 (file)
--- a/src/msg/msg_mailbox.c
+++ b/src/msg/msg_mailbox.c
@@ -42,7 +42,7 @@ void MSG_mailbox_free(void *mailbox)
 {
   msg_mailbox_t _mailbox = (msg_mailbox_t) mailbox;
 
-  if (NULL != (_mailbox->hostname))
+  if (_mailbox->hostname)
     free(_mailbox->hostname);
 
   xbt_fifo_free(_mailbox->tasks);
@@ -51,11 +51,6 @@ void MSG_mailbox_free(void *mailbox)
   free(_mailbox);
 }
 
-void MSG_mailbox_put(msg_mailbox_t mailbox, m_task_t task)
-{
-  xbt_fifo_push(mailbox->tasks, task);
-}
-
 smx_cond_t MSG_mailbox_get_cond(msg_mailbox_t mailbox)
 {
   return mailbox->cond;
@@ -80,7 +75,7 @@ m_task_t MSG_mailbox_get_head(msg_mailbox_t mailbox)
 {
   xbt_fifo_item_t item;
 
-  if (NULL == (item = xbt_fifo_get_first_item(mailbox->tasks)))
+  if (!(item = xbt_fifo_get_first_item(mailbox->tasks)))
     return NULL;
 
   return (m_task_t) xbt_fifo_get_item_content(item);
@@ -171,7 +166,7 @@ MSG_mailbox_get_task_ext(msg_mailbox_t mailbox, m_task_t * task,
   m_host_t h = NULL;
   simdata_task_t t_simdata = NULL;
   simdata_host_t h_simdata = NULL;
-  int first_time = 1;
+  double start_time = SIMIX_get_clock();
 
   smx_cond_t cond = NULL;      //conditional wait if the task isn't on the channel yet
 
@@ -206,51 +201,46 @@ MSG_mailbox_get_task_ext(msg_mailbox_t mailbox, m_task_t * task,
        break;
       } else {
        /* get the first task of the host */
-       if (NULL != (t = MSG_mailbox_get_first_host_task(mailbox, host)))
+       if ((t = MSG_mailbox_get_first_host_task(mailbox, host)))
          break;
       }
     }
 
-    if (timeout > 0) {
-      if (!first_time) {
-       SIMIX_mutex_unlock(h->simdata->mutex);
-       /* set the simix condition of the mailbox to NULL */
-       MSG_mailbox_set_cond(mailbox, NULL);
-       SIMIX_cond_destroy(cond);
-       MSG_RETURN(MSG_TRANSFER_FAILURE);
-      }
+    if ((timeout > 0) && (SIMIX_get_clock()-start_time>=timeout)) {
+      SIMIX_mutex_unlock(h->simdata->mutex);
+      MSG_mailbox_set_cond(mailbox, NULL);
+      SIMIX_cond_destroy(cond);
+      MSG_RETURN(MSG_TRANSFER_FAILURE);
     }
 
-    cond = SIMIX_cond_init();
-
-    /* set the condition of the mailbox */
-    MSG_mailbox_set_cond(mailbox, cond);
+    if(!cond) {
+      cond = SIMIX_cond_init();
+      MSG_mailbox_set_cond(mailbox, cond);
+    }
 
     if (timeout > 0)
-      SIMIX_cond_wait_timeout(cond, h->simdata->mutex, timeout);
+      SIMIX_cond_wait_timeout(cond, h->simdata->mutex, timeout-start_time);
     else
       SIMIX_cond_wait(MSG_mailbox_get_cond(mailbox), h->simdata->mutex);
 
-
     if (SIMIX_host_get_state(h_simdata->smx_host) == 0) {
+      SIMIX_mutex_unlock(h->simdata->mutex);
       MSG_mailbox_set_cond(mailbox, NULL);
       SIMIX_cond_destroy(cond);
       MSG_RETURN(MSG_HOST_FAILURE);
     }
-
-    first_time = 0;
   }
 
-  SIMIX_mutex_unlock(h->simdata->mutex);
 
   DEBUG1("OK, got a task (%s)", t->name);
   /* clean conditional */
   if (cond) {
-    SIMIX_cond_destroy(cond);
-
     MSG_mailbox_set_cond(mailbox, NULL);
+    SIMIX_cond_destroy(cond);
   }
 
+  SIMIX_mutex_unlock(h->simdata->mutex);
+
   t_simdata = t->simdata;
   t_simdata->receiver = process;
   *task = t;
@@ -266,6 +256,16 @@ MSG_mailbox_get_task_ext(msg_mailbox_t mailbox, m_task_t * task,
                               t->name, t_simdata->message_size,
                               t_simdata->rate);
 
+  /* This is a hack. We know that both the receiver and the sender will
+     need to look at the content of t_simdata->comm. And it needs to be
+     destroyed. However, we don't known whether the receiver or the sender
+     will get to it first. So by setting whit refcount to 2 we can enforce
+     that things happen correctly. An alternative would be to only do ++ and
+     -- on this refcount and to sprinkle them judiciously throughout the code,
+     which appears perhaps worse? Or perhaps the refcount field of
+     task->simdata can be used for this? At any rate, this will do for now */
+  t_simdata->comm->refcount = 2;
+
   /* if the process is suspend, create the action but stop its execution, it will be restart when the sender process resume */
   if (MSG_process_is_suspended(t_simdata->sender)) {
     DEBUG1("Process sender (%s) suspended", t_simdata->sender->name);
@@ -296,19 +296,31 @@ MSG_mailbox_get_task_ext(msg_mailbox_t mailbox, m_task_t * task,
 
 
   if (SIMIX_action_get_state(t_simdata->comm) == SURF_ACTION_DONE) {
-    SIMIX_action_destroy(t_simdata->comm);
-    t_simdata->comm = NULL;
-    t_simdata->using--;
+    if (t_simdata->comm->refcount == 1) {
+      SIMIX_action_destroy(t_simdata->comm);
+      t_simdata->comm = NULL;
+    } else {
+      t_simdata->comm->refcount --;
+    }
+    t_simdata->refcount --;
     MSG_RETURN(MSG_OK);
   } else if (SIMIX_host_get_state(h_simdata->smx_host) == 0) {
-    SIMIX_action_destroy(t_simdata->comm);
-    t_simdata->comm = NULL;
-    t_simdata->using--;
+    if (t_simdata->comm->refcount == 1) {
+      SIMIX_action_destroy(t_simdata->comm);
+      t_simdata->comm = NULL;
+    } else {
+      t_simdata->comm->refcount --;
+    }
+    t_simdata->refcount --;
     MSG_RETURN(MSG_HOST_FAILURE);
   } else {
-    SIMIX_action_destroy(t_simdata->comm);
-    t_simdata->comm = NULL;
-    t_simdata->using--;
+    if (t_simdata->comm->refcount ==1 ) {
+      SIMIX_action_destroy(t_simdata->comm);
+      t_simdata->comm = NULL;
+    } else {
+      t_simdata->comm->refcount --;
+    }
+    t_simdata->refcount --;
     MSG_RETURN(MSG_TRANSFER_FAILURE);
   }
 }
@@ -319,54 +331,53 @@ MSG_mailbox_put_with_timeout(msg_mailbox_t mailbox, m_task_t task,
 {
   m_process_t process = MSG_process_self();
   const char *hostname;
-  simdata_task_t task_simdata = NULL;
+  simdata_task_t t_simdata = NULL;
   m_host_t local_host = NULL;
   m_host_t remote_host = NULL;
   smx_cond_t cond = NULL;
 
   CHECK_HOST();
 
-  task_simdata = task->simdata;
-  task_simdata->sender = process;
-  task_simdata->source = MSG_process_get_host(process);
+  t_simdata = task->simdata;
+  t_simdata->sender = process;
+  t_simdata->source = MSG_process_get_host(process);
 
-  xbt_assert0(task_simdata->using == 1,
+  xbt_assert0(t_simdata->refcount  == 1,
              "This task is still being used somewhere else. You cannot send it now. Go fix your code!");
 
-  task_simdata->comm = NULL;
+  t_simdata->comm = NULL;
 
-  task_simdata->using++;
+  t_simdata->refcount ++;
   local_host = ((simdata_process_t) process->simdata)->m_host;
+  msg_global->sent_msg++;
 
   /* get the host name containing the mailbox */
   hostname = MSG_mailbox_get_hostname(mailbox);
 
   remote_host = MSG_get_host_by_name(hostname);
 
-  if (NULL == remote_host)
+  if (!remote_host)
     THROW1(not_found_error, 0, "Host %s not fount", hostname);
 
 
   DEBUG4
       ("Trying to send a task (%g kB) from %s to %s on the channel aliased by the alias %s",
-       task->simdata->message_size / 1000, local_host->name,
+       t_simdata->message_size / 1000, local_host->name,
        remote_host->name, MSG_mailbox_get_alias(mailbox));
 
   SIMIX_mutex_lock(remote_host->simdata->mutex);
 
   /* put the task in the mailbox */
-  MSG_mailbox_put(mailbox, task);
+  xbt_fifo_push(mailbox->tasks, task);
 
-  if (NULL != (cond = MSG_mailbox_get_cond(mailbox))) {
+  if ((cond = MSG_mailbox_get_cond(mailbox))) {
     DEBUG0("Somebody is listening. Let's wake him up!");
     SIMIX_cond_signal(cond);
   }
 
-
-
   SIMIX_mutex_unlock(remote_host->simdata->mutex);
 
-  SIMIX_mutex_lock(task->simdata->mutex);
+  SIMIX_mutex_lock(t_simdata->mutex);
 
   process->simdata->waiting_task = task;
 
@@ -380,11 +391,11 @@ MSG_mailbox_put_with_timeout(msg_mailbox_t mailbox, m_task_t task,
       /*verify if the action that ends is the correct. Call the wait_timeout with the new time. If the timeout occurs, an exception is raised */
       while (1) {
        time_elapsed = SIMIX_get_clock() - time;
-       SIMIX_cond_wait_timeout(task->simdata->cond, task->simdata->mutex,
+       SIMIX_cond_wait_timeout(t_simdata->cond, t_simdata->mutex,
                                timeout - time_elapsed);
 
-       if ((task->simdata->comm != NULL)
-           && (SIMIX_action_get_state(task->simdata->comm) !=
+       if ((t_simdata->comm != NULL)
+           && (SIMIX_action_get_state(t_simdata->comm) !=
                SURF_ACTION_RUNNING))
          break;
       }
@@ -393,19 +404,19 @@ MSG_mailbox_put_with_timeout(msg_mailbox_t mailbox, m_task_t task,
       if (e.category == timeout_error) {
        xbt_ex_free(e);
        /* verify if the timeout happened and the communication didn't started yet */
-       if (task->simdata->comm == NULL) {
+       if (t_simdata->comm == NULL) {
          process->simdata->waiting_task = NULL;
 
          /* remove the task from the mailbox */
          MSG_mailbox_remove(mailbox, task);
 
-         if (task->simdata->receiver) {
-           task->simdata->receiver->simdata->waiting_task = NULL;
+         if (t_simdata->receiver) {
+           t_simdata->receiver->simdata->waiting_task = NULL;
          }
 
-         task->simdata->sender = NULL;
+         t_simdata->sender = NULL;
 
-         SIMIX_mutex_unlock(task->simdata->mutex);
+         SIMIX_mutex_unlock(t_simdata->mutex);
          MSG_RETURN(MSG_TRANSFER_FAILURE);
        }
       } else {
@@ -414,9 +425,9 @@ MSG_mailbox_put_with_timeout(msg_mailbox_t mailbox, m_task_t task,
     }
   } else {
     while (1) {
-      SIMIX_cond_wait(task->simdata->cond, task->simdata->mutex);
+      SIMIX_cond_wait(t_simdata->cond, t_simdata->mutex);
 
-      if (SIMIX_action_get_state(task->simdata->comm) !=
+      if (SIMIX_action_get_state(t_simdata->comm) !=
          SURF_ACTION_RUNNING)
        break;
     }
@@ -426,19 +437,36 @@ MSG_mailbox_put_with_timeout(msg_mailbox_t mailbox, m_task_t task,
   process->simdata->waiting_task = NULL;
 
   /* the task has already finished and the pointer must be null */
-  if (task->simdata->receiver) {
-    task->simdata->receiver->simdata->waiting_task = NULL;
+  if (t_simdata->receiver) {
+    t_simdata->receiver->simdata->waiting_task = NULL;
   }
 
-  task->simdata->sender = NULL;
+  t_simdata->sender = NULL;
   SIMIX_mutex_unlock(task->simdata->mutex);
 
-
-  if (SIMIX_action_get_state(task->simdata->comm) == SURF_ACTION_DONE) {
+  if (SIMIX_action_get_state(t_simdata->comm) == SURF_ACTION_DONE) {
+    if (t_simdata->comm->refcount == 1) {
+      SIMIX_action_destroy(t_simdata->comm);
+      t_simdata->comm = NULL;
+    } else {
+      t_simdata->comm->refcount --;
+    }
     MSG_RETURN(MSG_OK);
   } else if (SIMIX_host_get_state(local_host->simdata->smx_host) == 0) {
+    if (t_simdata->comm->refcount == 1) {
+      SIMIX_action_destroy(t_simdata->comm);
+      t_simdata->comm = NULL;
+    } else {
+      t_simdata->comm->refcount --;
+    }
     MSG_RETURN(MSG_HOST_FAILURE);
   } else {
+    if (t_simdata->comm->refcount == 1) {
+      SIMIX_action_destroy(t_simdata->comm);
+      t_simdata->comm = NULL;
+    } else {
+      t_simdata->comm->refcount --;
+    }
     MSG_RETURN(MSG_TRANSFER_FAILURE);
   }
 }