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release_forever is supposed to open the latch. Let's do so
[simgrid.git] / src / simix / smx_synchro.c
index 1932708..e80c9cf 100644 (file)
 
 
 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_synchro, simix,
-                               "Logging specific to SIMIX (synchronization)");
+                                "Logging specific to SIMIX (synchronization)");
 
 
 /****************************** Synchronization *******************************/
 
 /*********************************** Mutex ************************************/
+
+/**
+ * \brief Initialize a mutex.
+ *
+ * Allocs and creates the data for the mutex. It have to be called before the utilisation of the mutex.
+ * \return A mutex
+ */
 smx_mutex_t SIMIX_mutex_init()
 {
-       smx_mutex_t m = xbt_new0(s_smx_mutex_t,1);
-       s_smx_process_t p; /* useful to initialize sleeping swag */
-       /* structures initialization */
-       m->using = 0;
-       m->sleeping = xbt_swag_new(xbt_swag_offset(p, synchro_hookup));
-       return m;
+  smx_mutex_t m = xbt_new0(s_smx_mutex_t, 1);
+  s_smx_process_t p;            /* useful to initialize sleeping swag */
+  /* structures initialization */
+  m->refcount = 0;
+  m->sleeping = xbt_swag_new(xbt_swag_offset(p, synchro_hookup));
+  return m;
 }
 
+/**
+ * \brief Locks a mutex.
+ *
+ * Tries to lock a mutex, if the mutex isn't used yet, the process can continue its execution, else it'll be blocked here. You have to call #SIMIX_mutex_unlock to free the mutex.
+ * \param mutex The mutex
+ */
 void SIMIX_mutex_lock(smx_mutex_t mutex)
 {
-       smx_process_t self = SIMIX_process_self();
-       xbt_assert0((mutex != NULL), "Invalid parameters");
-       
-
-       if (mutex->using) {
-               /* somebody using the mutex, block */
-               xbt_swag_insert(self, mutex->sleeping);
-               self->simdata->mutex = mutex;
-               /* wait for some process make the unlock and wake up me from mutex->sleeping */
-               xbt_context_yield();
-               self->simdata->mutex = NULL;
-
-               /* verify if the process was suspended */
-               while (self->simdata->suspended) {
-                       xbt_context_yield();
-               }
-
-               mutex->using = 1;
-       }
-       else {
-               /* mutex free */
-               mutex->using = 1;
-       }
-       return;
-}
-
-/* return 1 if the process got the mutex, else 0. */
-int SIMIX_mutex_trylock(smx_mutex_t mutex)
+  smx_process_t self = SIMIX_process_self();
+  xbt_assert0((mutex != NULL), "Invalid parameters");
+
+
+  if (mutex->refcount) {
+    /* somebody using the mutex, block */
+    xbt_swag_insert(self, mutex->sleeping);
+    self->mutex = mutex;
+    /* wait for some process make the unlock and wake up me from mutex->sleeping */
+    SIMIX_process_yield();
+    self->mutex = NULL;
+
+    /* verify if the process was suspended */
+    while (self->suspended) {
+      SIMIX_process_yield();
+    }
+
+    mutex->refcount = 1;
+  } else {
+    /* mutex free */
+    mutex->refcount = 1;
+  }
+  return;
+}
+
+/**
+ * \brief Tries to lock a mutex.
+ *
+ * Tries to lock a mutex, return 1 if the mutex is free, 0 else. This function does not block the process if the mutex is used.
+ * \param mutex The mutex
+ * \return 1 - mutex free, 0 - mutex used
+ */
+XBT_INLINE int SIMIX_mutex_trylock(smx_mutex_t mutex)
 {
-       xbt_assert0((mutex != NULL), "Invalid parameters");
-       
-       if (mutex->using) 
-               return 0;
-       else {
-               mutex->using = 1;
-               return 1;
-       }
+  xbt_assert0((mutex != NULL), "Invalid parameters");
+
+  if (mutex->refcount)
+    return 0;
+  else {
+    mutex->refcount = 1;
+    return 1;
+  }
 }
 
+/**
+ * \brief Unlocks a mutex.
+ *
+ * Unlocks the mutex and wakes up a process blocked on it. If there are no process sleeping, only sets the mutex as free.
+ * \param mutex The mutex
+ */
 void SIMIX_mutex_unlock(smx_mutex_t mutex)
 {
-       smx_process_t p;        /*process to wake up */
-       
-       xbt_assert0((mutex != NULL), "Invalid parameters");
-       
-       if (xbt_swag_size(mutex->sleeping) > 0) {
-               p = xbt_swag_extract(mutex->sleeping);
-               mutex->using = 0;
-               xbt_swag_insert(p, simix_global->process_to_run);
-       }
-       else {
-               /* nobody to wake up */
-               mutex->using = 0;
-       }
-       return;
-}
-
-void SIMIX_mutex_destroy(smx_mutex_t mutex)
+  smx_process_t p;              /*process to wake up */
+
+  xbt_assert0((mutex != NULL), "Invalid parameters");
+
+  if (xbt_swag_size(mutex->sleeping) > 0) {
+    p = xbt_swag_extract(mutex->sleeping);
+    mutex->refcount = 0;
+    xbt_swag_insert(p, simix_global->process_to_run);
+  } else {
+    /* nobody to wake up */
+    mutex->refcount = 0;
+  }
+  return;
+}
+
+/**
+ * \brief Destroys a mutex.
+ *
+ * Destroys and frees the mutex's memory. 
+ * \param mutex A mutex
+ */
+XBT_INLINE void SIMIX_mutex_destroy(smx_mutex_t mutex)
 {
-       if ( mutex == NULL )
-               return ;
-       else {
-               xbt_swag_free(mutex->sleeping);
-               xbt_free(mutex);
-               return ;
-       }
+  if (mutex == NULL)
+    return;
+  else {
+    xbt_swag_free(mutex->sleeping);
+    xbt_free(mutex);
+    return;
+  }
 }
 
 /******************************** Conditional *********************************/
+
+/**
+ * \brief Initialize a condition.
+ *
+ * Allocates and creates the data for the condition.
+ * It have to be called before the use of the condition.
+ * \return A condition
+ */
 smx_cond_t SIMIX_cond_init()
 {
-       smx_cond_t cond = xbt_new0(s_smx_cond_t,1);
-       s_smx_process_t p;
-       
-       cond->sleeping = xbt_swag_new(xbt_swag_offset(p,synchro_hookup));
-       cond->actions = xbt_fifo_new();
-       cond->mutex = NULL;
-       return cond;
+  smx_cond_t cond = xbt_new0(s_smx_cond_t, 1);
+  s_smx_process_t p;
+
+  cond->sleeping = xbt_swag_new(xbt_swag_offset(p, synchro_hookup));
+  cond->actions = xbt_fifo_new();
+  cond->mutex = NULL;
+  return cond;
 }
 
+/**
+ * \brief Signalizes a condition.
+ *
+ * Signalizes a condition and wakes up a sleeping process. If there are no process sleeping, no action is done.
+ * \param cond A condition
+ */
 void SIMIX_cond_signal(smx_cond_t cond)
 {
-       xbt_assert0((cond != NULL), "Invalid parameters");
-       smx_process_t proc = NULL;
+  smx_process_t proc = NULL;
+  DEBUG1("Signal condition %p", cond);
+  xbt_assert0((cond != NULL), "Invalid parameters");
 
-       if (xbt_swag_size(cond->sleeping) >= 1) {
-               proc = xbt_swag_extract(cond->sleeping);
-               xbt_swag_insert(proc, simix_global->process_to_run);
-       }
 
-       return;
+  if (xbt_swag_size(cond->sleeping) >= 1) {
+    proc = xbt_swag_extract(cond->sleeping);
+    xbt_swag_insert(proc, simix_global->process_to_run);
+  }
+
+  return;
 }
 
-void SIMIX_cond_wait(smx_cond_t cond,smx_mutex_t mutex)
+/**
+ * \brief Waits on a condition.
+ *
+ * Blocks a process until the signal is called. This functions frees the mutex associated and locks it after its execution.
+ * \param cond A condition
+ * \param mutex A mutex
+ */
+void SIMIX_cond_wait(smx_cond_t cond, smx_mutex_t mutex)
 {
-       smx_action_t act_sleep;
-       xbt_assert0((mutex != NULL), "Invalid parameters");
-       
-       cond->mutex = mutex;
-
-       SIMIX_mutex_unlock(mutex);
-       /* create an action null only if there are no actions already on the condition, usefull if the host crashs */
-       if (xbt_fifo_size(cond->actions) ==0 ) {
-               act_sleep = SIMIX_action_sleep(SIMIX_host_self(), -1);
-               SIMIX_register_action_to_condition(act_sleep,cond);
-               SIMIX_register_condition_to_action(act_sleep,cond);
-               __SIMIX_cond_wait(cond);
-               xbt_fifo_pop(act_sleep->cond_list);
-               SIMIX_action_destroy(act_sleep);
-       }
-       else {
-               __SIMIX_cond_wait(cond);
-       }
-       /* get the mutex again */
-       SIMIX_mutex_lock(cond->mutex);
-
-       return;
+  smx_action_t act_sleep;
+
+  DEBUG1("Wait condition %p", cond);
+
+  /* If there is a mutex unlock it */
+  if(mutex != NULL){
+    cond->mutex = mutex;
+    SIMIX_mutex_unlock(mutex);
+  }
+  
+  /* Always create an action null in case there is a host failure */
+  act_sleep = SIMIX_action_sleep(SIMIX_host_self(), -1);
+  SIMIX_action_set_name(act_sleep,bprintf("Wait condition %p", cond));
+  SIMIX_process_self()->waiting_action = act_sleep;
+  SIMIX_register_action_to_condition(act_sleep, cond);
+  __SIMIX_cond_wait(cond);
+  SIMIX_process_self()->waiting_action = NULL;
+  SIMIX_unregister_action_to_condition(act_sleep, cond);
+  SIMIX_action_destroy(act_sleep);
+
+  /* get the mutex again if necessary */
+  if(mutex != NULL)
+    SIMIX_mutex_lock(cond->mutex);
+
+  return;
 }
 
-void __SIMIX_cond_wait(smx_cond_t cond)
+XBT_INLINE xbt_fifo_t SIMIX_cond_get_actions(smx_cond_t cond)
 {
-       smx_process_t self = SIMIX_process_self();
-       xbt_assert0((cond != NULL), "Invalid parameters");
-       
-       /* process status */    
-
-       self->simdata->cond = cond;
-       xbt_swag_insert(self, cond->sleeping);
-       xbt_context_yield();
-       self->simdata->cond = NULL;
-       while (self->simdata->suspended) {
-               xbt_context_yield();
-       }
-       return;
-
+  xbt_assert0((cond != NULL), "Invalid parameters");
+  return cond->actions;
 }
 
-void SIMIX_cond_wait_timeout(smx_cond_t cond,smx_mutex_t mutex, double max_duration)
+void __SIMIX_cond_wait(smx_cond_t cond)
 {
-       xbt_assert0((mutex != NULL), "Invalid parameters");
-       smx_action_t act_sleep;
-
-       cond->mutex = mutex;
-
-       SIMIX_mutex_unlock(mutex);
-       if (max_duration >=0) {
-               act_sleep = SIMIX_action_sleep(SIMIX_host_self(), max_duration);
-               SIMIX_register_action_to_condition(act_sleep,cond);
-               SIMIX_register_condition_to_action(act_sleep,cond);
-       }
-       __SIMIX_cond_wait(cond);
-
-       /* get the mutex again */
-       SIMIX_mutex_lock(cond->mutex);
+  smx_process_t self = SIMIX_process_self();
+  xbt_assert0((cond != NULL), "Invalid parameters");
+
+  /* process status */
+
+  self->cond = cond;
+  xbt_swag_insert(self, cond->sleeping);
+  SIMIX_process_yield();
+  self->cond = NULL;
+  while (self->suspended) {
+    SIMIX_process_yield();
+  }
+  return;
+}
 
-       return;
+/**
+ * \brief Waits on a condition with timeout.
+ *
+ * Same behavior of #SIMIX_cond_wait, but waits a maximum time and throws an timeout_error if it happens.
+ * \param cond A condition
+ * \param mutex A mutex
+ * \param max_duration Timeout time
+ */
+void SIMIX_cond_wait_timeout(smx_cond_t cond, smx_mutex_t mutex,
+                             double max_duration)
+{
+  smx_action_t act_sleep;
+
+  DEBUG1("Timed wait condition %p", cond);
+
+  /* If there is a mutex unlock it */
+  if(mutex != NULL){
+    cond->mutex = mutex;
+    SIMIX_mutex_unlock(mutex);
+  }
+
+  if (max_duration >= 0) {
+    act_sleep = SIMIX_action_sleep(SIMIX_host_self(), max_duration);
+    SIMIX_action_set_name(act_sleep,bprintf("Timed wait condition %p (max_duration:%f)", cond,max_duration));
+    SIMIX_register_action_to_condition(act_sleep, cond);
+    SIMIX_process_self()->waiting_action = act_sleep;
+    __SIMIX_cond_wait(cond);
+    SIMIX_process_self()->waiting_action = NULL;
+    SIMIX_unregister_action_to_condition(act_sleep, cond);
+    if (SIMIX_action_get_state(act_sleep) == SURF_ACTION_DONE) {
+      SIMIX_action_destroy(act_sleep);
+      THROW1(timeout_error, 0, "Condition timeout after %f",max_duration);
+    } else {
+      SIMIX_action_destroy(act_sleep);
+    }
+
+  } else
+    SIMIX_cond_wait(cond,NULL);
+
+  /* get the mutex again if necessary */
+  if(mutex != NULL)
+    SIMIX_mutex_lock(cond->mutex);
 }
 
+/**
+ * \brief Broadcasts a condition.
+ *
+ * Signalizes a condition and wakes up ALL sleping process. If there are no process sleeping, no action is done.
+ * \param cond A condition
+ */
 void SIMIX_cond_broadcast(smx_cond_t cond)
 {
-       xbt_assert0((cond != NULL), "Invalid parameters");
-       smx_process_t proc = NULL;
-       smx_process_t proc_next = NULL;
+  smx_process_t proc = NULL;
+  smx_process_t proc_next = NULL;
 
-       xbt_swag_foreach_safe(proc,proc_next,cond->sleeping) {
-               xbt_swag_remove(proc,cond->sleeping);
-               xbt_swag_insert(proc, simix_global->process_to_run);
-       }
+  xbt_assert0((cond != NULL), "Invalid parameters");
 
-       return;
+  DEBUG1("Broadcast condition %p", cond);
+  xbt_swag_foreach_safe(proc, proc_next, cond->sleeping) {
+    xbt_swag_remove(proc, cond->sleeping);
+    xbt_swag_insert(proc, simix_global->process_to_run);
+  }
 }
 
+/**
+ * \brief Destroys a contidion.
+ *
+ * Destroys and frees the condition's memory. 
+ * \param cond A condition
+ */
 void SIMIX_cond_destroy(smx_cond_t cond)
 {
-       if ( cond == NULL )
-               return ;
-       else {
-               xbt_assert0( xbt_swag_size(cond->sleeping) == 0 , "Cannot destroy conditional");
-               xbt_swag_free(cond->sleeping);
-               xbt_fifo_free(cond->actions);
-               xbt_free(cond);
-               return;
-       }
-}
-
-void SIMIX_register_condition_to_action(smx_action_t action, smx_cond_t cond)
+  DEBUG1("Destroy condition %p", cond);
+  if (cond == NULL)
+    return;
+  else {
+    xbt_fifo_item_t item = NULL;
+    smx_action_t action = NULL;
+
+    xbt_assert0(xbt_swag_size(cond->sleeping) == 0,
+                "Cannot destroy conditional since someone is still using it");
+    xbt_swag_free(cond->sleeping);
+
+    DEBUG1("%d actions registered", xbt_fifo_size(cond->actions));
+    __SIMIX_cond_display_actions(cond);
+    xbt_fifo_foreach(cond->actions, item, action, smx_action_t) {
+      SIMIX_unregister_action_to_condition(action, cond);
+    }
+    __SIMIX_cond_display_actions(cond);
+
+    xbt_fifo_free(cond->actions);
+    xbt_free(cond);
+    return;
+  }
+}
+
+void SIMIX_cond_display_info(smx_cond_t cond)
 {
-       xbt_assert0( (action != NULL) && (cond != NULL), "Invalid parameters");
+  if (cond == NULL)
+    return;
+  else {
+    smx_process_t process = NULL;
+
+    INFO0("Blocked process on this condition:");
+    xbt_swag_foreach(process, cond->sleeping) {
+      INFO2("\t %s running on host %s", process->name,
+            process->smx_host->name);
+    }
+  }
+}
+
+/* ************************** Semaphores ************************************** */
+#define SMX_SEM_NOLIMIT 99999
+/** @brief Initialize a semaphore */
+smx_sem_t SIMIX_sem_init(int capacity) {
+  smx_sem_t sem = xbt_new0(s_smx_sem_t, 1);
+  s_smx_process_t p;
+
+  sem->sleeping = xbt_swag_new(xbt_swag_offset(p, synchro_hookup));
+  sem->actions = xbt_fifo_new();
+  sem->capacity = capacity;
+  return sem;
+}
+/** @brief Destroys a semaphore */
+void SIMIX_sem_destroy(smx_sem_t sem) {
+  DEBUG1("Destroy semaphore %p", sem);
+  if (sem == NULL)
+    return;
+
+  smx_action_t action = NULL;
+
+  xbt_assert0(xbt_swag_size(sem->sleeping) == 0,
+      "Cannot destroy semaphore since someone is still using it");
+  xbt_swag_free(sem->sleeping);
+
+  DEBUG1("%d actions registered", xbt_fifo_size(sem->actions));
+  while((action=xbt_fifo_pop(sem->actions)))
+    SIMIX_unregister_action_to_semaphore(action, sem);
+
+  xbt_fifo_free(sem->actions);
+  xbt_free(sem);
+}
 
-       xbt_fifo_push(action->cond_list,cond);
+/** @brief release the semaphore
+ *
+ * The first locked process on this semaphore is unlocked.
+ * If no one was blocked, the semaphore capacity is increased by 1.
+ * */
+void SIMIX_sem_release(smx_sem_t sem) {
+       DEBUG1("Sem release semaphore %p", sem);
+  if (xbt_swag_size(sem->sleeping) >= 1) {
+    smx_process_t proc = xbt_swag_extract(sem->sleeping);
+    xbt_swag_insert(proc, simix_global->process_to_run);
+  } else if (sem->capacity != SMX_SEM_NOLIMIT) {
+    sem->capacity++;
+  }
+}
+/** @brief make sure the semaphore will never be blocking again
+ *
+ * This function is not really in the semaphore spirit. It makes
+ * sure that the semaphore will never be blocking anymore.
+ *
+ * Releasing and acquiring the semaphore after calling this
+ * function is a noop. Such "broken" semaphores are useful to
+ * implement something between condition variables (with broadcast)
+ * and semaphore (with memory). It's like a semaphore signaled for ever.
+ *
+ * There is no way to reset the semaphore to a more regular state afterward.
+ * */
+void SIMIX_sem_release_forever(smx_sem_t sem) {
+  smx_process_t proc = NULL;
+  smx_process_t proc_next = NULL;
+
+  DEBUG1("Broadcast semaphore %p", sem);
+  xbt_swag_foreach_safe(proc, proc_next, sem->sleeping) {
+    xbt_swag_remove(proc, sem->sleeping);
+    xbt_swag_insert(proc, simix_global->process_to_run);
+  }
+  sem->capacity == SMX_SEM_NOLIMIT;
 }
 
+/**
+ * \brief Low level wait on a semaphore
+ *
+ * This function does not test the capacity of the semaphore and direcly locks
+ * the calling process on the semaphore (until someone call SIMIX_sem_release()
+ * on this semaphore). Do not call this function if you did not attach any action
+ * to this semaphore to be awaken. Note also that you may miss host failure if you
+ * do not attach a dummy action beforehand. SIMIX_sem_acquire does all these
+ * things for you so you it may be preferable to use.
+ */
+void SIMIX_sem_block_onto(smx_sem_t sem) {
+  smx_process_t self = SIMIX_process_self();
+
+  /* process status */
+  self->sem = sem;
+  xbt_swag_insert(self, sem->sleeping);
+  SIMIX_process_yield();
+  self->sem = NULL;
+  while (self->suspended)
+    SIMIX_process_yield();
+}
 
+/** @brief Returns true if acquiring this semaphore would block */
+XBT_INLINE int SIMIX_sem_would_block(smx_sem_t sem) {
+  return (sem->capacity>0);
+}
+
+/** @brief Returns the current capacity of the semaphore
+ *
+ * If it's negative, that's the amount of processes locked on the semaphore
+ */
+int SIMIX_sem_get_capacity(smx_sem_t sem){
+  return sem->capacity;
+}
+
+/**
+ * \brief Waits on a semaphore
+ *
+ * If the capacity>0, decrease the capacity.
+ *
+ * If capacity==0, locks the current process
+ * until someone call SIMIX_sem_release() on this semaphore
+ */
+void SIMIX_sem_acquire(smx_sem_t sem) {
+  smx_action_t act_sleep;
+
+  DEBUG1("Wait semaphore %p", sem);
+
+  if (sem->capacity == SMX_SEM_NOLIMIT)
+    return; /* don't even decrease it if wide open */
+
+  /* If capacity sufficient, decrease it */
+  if (sem->capacity>0) {
+    sem->capacity--;
+    return;
+  }
+
+  sem->capacity--;
+  /* Always create an action null in case there is a host failure */
+  act_sleep = SIMIX_action_sleep(SIMIX_host_self(), -1);
+  SIMIX_action_set_name(act_sleep,bprintf("Locked in semaphore %p", sem));
+  SIMIX_process_self()->waiting_action = act_sleep;
+  SIMIX_register_action_to_semaphore(act_sleep, sem);
+  SIMIX_sem_block_onto(sem);
+  SIMIX_process_self()->waiting_action = NULL;
+  SIMIX_unregister_action_to_semaphore(act_sleep, sem);
+  SIMIX_action_destroy(act_sleep);
+  DEBUG1("End of Wait on semaphore %p", sem);
+  sem->capacity++;
+}
+/**
+ * \brief Tries to acquire a semaphore before a timeout
+ *
+ * Same behavior of #SIMIX_sem_acquire, but waits a maximum time and throws an timeout_error if it happens.
+ */
+void SIMIX_sem_acquire_timeout(smx_sem_t sem, double max_duration) {
+  smx_action_t act_sleep;
+
+  DEBUG2("Timed wait semaphore %p (timeout:%f)", sem,max_duration);
+
+  if (sem->capacity == SMX_SEM_NOLIMIT)
+    return; /* don't even decrease it if wide open */
+
+  /* If capacity sufficient, decrease it */
+  if (sem->capacity>0) {
+    sem->capacity--;
+    return;
+  }
+
+  if (max_duration >= 0) {
+    sem->capacity--;
+    act_sleep = SIMIX_action_sleep(SIMIX_host_self(), max_duration);
+    SIMIX_action_set_name(act_sleep,bprintf("Timed wait semaphore %p (max_duration:%f)", sem,max_duration));
+    SIMIX_register_action_to_semaphore(act_sleep, sem);
+    SIMIX_process_self()->waiting_action = act_sleep;
+    SIMIX_sem_block_onto(sem);
+    SIMIX_process_self()->waiting_action = NULL;
+    SIMIX_unregister_action_to_semaphore(act_sleep, sem);
+    if (SIMIX_action_get_state(act_sleep) == SURF_ACTION_DONE) {
+      SIMIX_action_destroy(act_sleep);
+      THROW1(timeout_error, 0, "Semaphore acquire timeouted after %f",max_duration);
+    } else {
+      SIMIX_action_destroy(act_sleep);
+    }
+    sem->capacity++;
+
+  } else
+    SIMIX_sem_acquire(sem);
+}
+/**
+ * \brief Blocks on a set of semaphore
+ *
+ * If any of the semaphores has some more capacity, it gets decreased.
+ * If not, blocks until the capacity of one of the semaphores becomes more friendly.
+ *
+ * \return the rank in the dynar of the semaphore which just got locked from the set
+ */
+unsigned int SIMIX_sem_acquire_any(xbt_dynar_t sems) {
+  smx_sem_t sem;
+  unsigned int counter,result=-1;
+  smx_action_t act_sleep;
+  smx_process_t self = SIMIX_process_self();
+
+  xbt_assert0(xbt_dynar_length(sems),
+      "I refuse to commit sucide by locking on an **empty** set of semaphores!!");
+  DEBUG1("Wait on semaphore set %p", sems);
+
+  xbt_dynar_foreach(sems,counter,sem) {
+    if (!SIMIX_sem_would_block(sem))
+      SIMIX_sem_acquire(sem);
+    return counter;
+  }
+
+  /* Always create an action null in case there is a host failure */
+  act_sleep = SIMIX_action_sleep(SIMIX_host_self(), -1);
+  SIMIX_action_set_name(act_sleep,bprintf("Locked in semaphore %p", sem));
+  self->waiting_action = act_sleep;
+  SIMIX_register_action_to_semaphore(act_sleep, xbt_dynar_get_as(sems,0,smx_sem_t));
+
+  /* Get listed as member of all the provided semaphores */
+  self->sem = (smx_sem_t)sems; /* FIXME: we pass a pointer to dynar where a pointer to sem is expected...*/
+  xbt_dynar_foreach(sems,counter,sem) {
+    xbt_swag_insert(self, sem->sleeping);
+  }
+  SIMIX_process_yield();
+  while (self->suspended)
+    SIMIX_process_yield();
+
+  /* one of the semaphore unsuspended us -- great, let's search which one (and get out of the others) */
+  self->sem = NULL;
+  xbt_dynar_foreach(sems,counter,sem) {
+    if (xbt_swag_belongs(self,sem->sleeping))
+      xbt_swag_remove(self,sem->sleeping);
+    else {
+      xbt_assert0(result==-1,"More than one semaphore unlocked us. Dunno what to do");
+      result = counter;
+    }
+  }
+  xbt_assert0(counter!=-1,"Cannot find which semaphore unlocked me!");
+
+  /* Destroy the waiting action */
+  self->waiting_action = NULL;
+  SIMIX_unregister_action_to_semaphore(act_sleep, xbt_dynar_get_as(sems,0,smx_sem_t));
+  SIMIX_action_destroy(act_sleep);
+  return result;
+}