Logo AND Algorithmique Numérique Distribuée

Public GIT Repository
Kill a static function raising 'not implemented' which landed in the documentation...
[simgrid.git] / src / msg / gos.c
index fcd53b2..321bfef 100644 (file)
 /*     $Id$      */
-  
+
 /* Copyright (c) 2002-2007 Arnaud Legrand.                                  */
 /* Copyright (c) 2007 Bruno Donassolo.                                      */
 /* All rights reserved.                                                     */
 
 /* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */
-  
+
 #include "msg/private.h"
 #include "xbt/sysdep.h"
 #include "xbt/log.h"
+#include "mailbox.h"
 
-XBT_LOG_NEW_DEFAULT_SUBCATEGORY(msg_gos, msg, "Logging specific to MSG (gos)");
 
-/** \defgroup msg_gos_functions MSG Operating System Functions
- *  \brief This section describes the functions that can be used
- *  by an agent for handling some task.
+XBT_LOG_NEW_DEFAULT_SUBCATEGORY(msg_gos, msg,
+                                "Logging specific to MSG (gos)");
+
+/** \ingroup msg_gos_functions
+ *
+ * \brief Return the last value returned by a MSG function (except
+ * MSG_get_errno...).
  */
+MSG_error_t MSG_get_errno(void)
+{
+  return PROCESS_GET_ERRNO();
+}
 
-static MSG_error_t __MSG_task_get_with_time_out_from_host(m_task_t * task,
-                                                       m_channel_t channel,
-                                                       double max_duration,
-                                                       m_host_t host)
+/** \ingroup msg_gos_functions
+ * \brief Executes a task and waits for its termination.
+ *
+ * This function is used for describing the behavior of an agent. It
+ * takes only one parameter.
+ * \param task a #m_task_t to execute on the location on which the
+   agent is running.
+ * \return #MSG_FATAL if \a task is not properly initialized and
+ * #MSG_OK otherwise.
+ */
+MSG_error_t MSG_task_execute(m_task_t task)
 {
+  simdata_task_t simdata = NULL;
+  m_process_t self = MSG_process_self();
+  e_surf_action_state_t state = SURF_ACTION_NOT_IN_THE_SYSTEM;
+  CHECK_HOST();
 
-  m_process_t process = MSG_process_self();
-  m_task_t t = NULL;
-  m_host_t h = NULL;
-  simdata_task_t t_simdata = NULL;
-  simdata_host_t h_simdata = NULL;
-  int first_time = 1;
-  xbt_fifo_item_t item = NULL;
+  simdata = task->simdata;
+  xbt_assert1((!simdata->compute)
+              && (task->simdata->refcount == 1),
+              "This task is executed somewhere else. Go fix your code! %d", task->simdata->refcount);
+
+  DEBUG1("Computing on %s", MSG_process_self()->simdata->m_host->name);
+
+  simdata->refcount++;
+  SIMIX_mutex_lock(simdata->mutex);
+  simdata->compute =
+    SIMIX_action_execute(SIMIX_host_self(), task->name,
+                         simdata->computation_amount);
+  SIMIX_action_set_priority(simdata->compute, simdata->priority);
+
+  /* changed to waiting action since we are always waiting one action (execute, communicate or sleep) */
+  self->simdata->waiting_action = simdata->compute;
+  SIMIX_register_action_to_condition(simdata->compute, simdata->cond);
+  do {
+    SIMIX_cond_wait(simdata->cond, simdata->mutex);
+    state = SIMIX_action_get_state(simdata->compute);
+  } while (state == SURF_ACTION_READY || state == SURF_ACTION_RUNNING);
+  SIMIX_unregister_action_to_condition(simdata->compute, simdata->cond);
+  self->simdata->waiting_action = NULL;
+
+  SIMIX_mutex_unlock(simdata->mutex);
+  simdata->refcount--;
+
+  if (SIMIX_action_get_state(task->simdata->compute) == SURF_ACTION_DONE) {
+    /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
+    SIMIX_action_destroy(task->simdata->compute);
+    simdata->computation_amount = 0.0;
+    simdata->comm = NULL;
+    simdata->compute = NULL;
+    MSG_RETURN(MSG_OK);
+  } else if (SIMIX_host_get_state(SIMIX_host_self()) == 0) {
+    /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
+    SIMIX_action_destroy(task->simdata->compute);
+    simdata->comm = NULL;
+    simdata->compute = NULL;
+    MSG_RETURN(MSG_HOST_FAILURE);
+  } else {
+    /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
+    SIMIX_action_destroy(task->simdata->compute);
+    simdata->comm = NULL;
+    simdata->compute = NULL;
+    MSG_RETURN(MSG_TASK_CANCELLED);
+  }
+}
+
+/** \ingroup m_task_management
+ * \brief Creates a new #m_task_t (a parallel one....).
+ *
+ * A constructor for #m_task_t taking six arguments and returning the
+   corresponding object.
+ * \param name a name for the object. It is for user-level information
+   and can be NULL.
+ * \param host_nb the number of hosts implied in the parallel task.
+ * \param host_list an array of \p host_nb m_host_t.
+ * \param computation_amount an array of \p host_nb
+   doubles. computation_amount[i] is the total number of operations
+   that have to be performed on host_list[i].
+ * \param communication_amount an array of \p host_nb* \p host_nb doubles.
+ * \param data a pointer to any data may want to attach to the new
+   object.  It is for user-level information and can be NULL. It can
+   be retrieved with the function \ref MSG_task_get_data.
+ * \see m_task_t
+ * \return The new corresponding object.
+ */
+m_task_t
+MSG_parallel_task_create(const char *name, int host_nb,
+                         const m_host_t * host_list,
+                         double *computation_amount,
+                         double *communication_amount, void *data)
+{
+  int i;
+  simdata_task_t simdata = xbt_new0(s_simdata_task_t, 1);
+  m_task_t task = xbt_new0(s_m_task_t, 1);
+  task->simdata = simdata;
+
+  /* Task structure */
+  task->name = xbt_strdup(name);
+  task->data = data;
+
+  /* Simulator Data */
+  simdata->computation_amount = 0;
+  simdata->message_size = 0;
+  simdata->cond = SIMIX_cond_init();
+  simdata->mutex = SIMIX_mutex_init();
+  simdata->compute = NULL;
+  simdata->comm = NULL;
+  simdata->rate = -1.0;
+  simdata->refcount = 1;
+  simdata->sender = NULL;
+  simdata->receiver = NULL;
+  simdata->source = NULL;
 
-       smx_cond_t cond = NULL;                 //conditional wait if the task isn't on the channel yet
+  simdata->host_nb = host_nb;
+  simdata->host_list = xbt_new0(smx_host_t, host_nb);
+  simdata->comp_amount = computation_amount;
+  simdata->comm_amount = communication_amount;
+
+  for (i = 0; i < host_nb; i++)
+    simdata->host_list[i] = host_list[i]->simdata->smx_host;
+
+  return task;
+}
 
+MSG_error_t MSG_parallel_task_execute(m_task_t task)
+{
+  simdata_task_t simdata = NULL;
+  m_process_t self = MSG_process_self();
+  e_surf_action_state_t state = SURF_ACTION_NOT_IN_THE_SYSTEM;
   CHECK_HOST();
-  xbt_assert1((channel>=0) && (channel < msg_global->max_channel),"Invalid channel %d",channel);
-  /* Sanity check */
-  xbt_assert0(task,"Null pointer for the task\n");
-
-  if (*task) 
-    CRITICAL0("MSG_task_get() was asked to write in a non empty task struct.");
-
-  /* Get the task */
-  h = MSG_host_self();
-  h_simdata = h->simdata;
-
-  DEBUG2("Waiting for a task on channel %d (%s)", channel,h->name);
-
-       SIMIX_mutex_lock(h->simdata->mutex);
-  while (1) {
-               if(xbt_fifo_size(h_simdata->mbox[channel])>0) {
-                       if(!host) {
-                               t = xbt_fifo_shift(h_simdata->mbox[channel]);
-                               break;
-                       } else {
-                               xbt_fifo_foreach(h->simdata->mbox[channel],item,t,m_task_t) {
-                                       if(t->simdata->source==host) break;
-                               }
-                               if(item) {
-                                       xbt_fifo_remove_item(h->simdata->mbox[channel],item);
-                                       break;
-                               } 
-                       }
-               }
-               
-               if(max_duration>0) {
-                       if(!first_time) {
-                               SIMIX_mutex_unlock(h->simdata->mutex);
-                               h_simdata->sleeping[channel] = NULL;
-                               SIMIX_cond_destroy(cond);
-                               MSG_RETURN(MSG_TRANSFER_FAILURE);
-                       }
-               }
-               xbt_assert1(!(h_simdata->sleeping[channel]),"A process is already blocked on channel %d", channel);
-       
-               cond = SIMIX_cond_init();
-               h_simdata->sleeping[channel] = cond;
-               if (max_duration > 0) {
-                       SIMIX_cond_wait_timeout(cond, h->simdata->mutex, max_duration);
-               }
-               else SIMIX_cond_wait(h_simdata->sleeping[channel],h->simdata->mutex);
-
-               if(SIMIX_host_get_state(h_simdata->host)==0)
-      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);
-               h_simdata->sleeping[channel] = NULL;
-       }
-
-  t_simdata = t->simdata;
-       t_simdata->receiver = process;
-  *task=t;
-
-       SIMIX_mutex_lock(t_simdata->mutex);
-
-  /* Transfer */
-  t_simdata->using++;
-       /* create SIMIX action to the communication */
-       t_simdata->comm = SIMIX_action_communicate(t_simdata->sender->simdata->host->simdata->host,
-                                                                                                                                                                               process->simdata->host->simdata->host,t->name, t_simdata->message_size, 
-                                                                                                                                                                               t_simdata->rate); 
-       /* 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);
-               SIMIX_action_set_priority(t_simdata->comm,0);
-       }
-       process->simdata->waiting_task = t;
-       SIMIX_register_action_to_condition(t_simdata->comm, t_simdata->cond);
-       SIMIX_register_condition_to_action(t_simdata->comm, t_simdata->cond);
-       SIMIX_cond_wait(t_simdata->cond,t_simdata->mutex);
-       process->simdata->waiting_task = NULL;
-
-       /* the task has already finished and the pointer must be null*/
-       if (t->simdata->sender) {
-               t->simdata->sender->simdata->waiting_task = NULL;
-               /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
-               //t->simdata->comm = NULL;
-               //t->simdata->compute = NULL;
-       }
-       /* for this process, don't need to change in get function*/
-       t->simdata->receiver = NULL;
-       SIMIX_mutex_unlock(t_simdata->mutex);
-
-
-       if(SIMIX_action_get_state(t_simdata->comm) == SURF_ACTION_DONE) {
-               //t_simdata->comm = NULL;
-               SIMIX_action_destroy(t_simdata->comm);
-               t_simdata->comm = NULL;
+  simdata = task->simdata;
+
+  xbt_assert0((!simdata->compute)
+              && (task->simdata->refcount == 1),
+              "This task is executed somewhere else. Go fix your code!");
+
+  xbt_assert0(simdata->host_nb, "This is not a parallel task. Go to hell.");
+
+  DEBUG1("Computing on %s", MSG_process_self()->simdata->m_host->name);
+
+  simdata->refcount++;
+
+  SIMIX_mutex_lock(simdata->mutex);
+  simdata->compute =
+    SIMIX_action_parallel_execute(task->name, simdata->host_nb,
+                                  simdata->host_list, simdata->comp_amount,
+                                  simdata->comm_amount, 1.0, -1.0);
+
+  self->simdata->waiting_action = simdata->compute;
+  SIMIX_register_action_to_condition(simdata->compute, simdata->cond);
+  do {
+    SIMIX_cond_wait(simdata->cond, simdata->mutex);
+    state = SIMIX_action_get_state(task->simdata->compute);
+  } while (state == SURF_ACTION_READY || state == SURF_ACTION_RUNNING);
+
+  SIMIX_unregister_action_to_condition(simdata->compute, simdata->cond);
+  self->simdata->waiting_action = NULL;
+
+
+  SIMIX_mutex_unlock(simdata->mutex);
+  simdata->refcount--;
+
+  if (SIMIX_action_get_state(task->simdata->compute) == SURF_ACTION_DONE) {
+    /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
+    SIMIX_action_destroy(task->simdata->compute);
+    simdata->computation_amount = 0.0;
+    simdata->comm = NULL;
+    simdata->compute = NULL;
     MSG_RETURN(MSG_OK);
-       } else if (SIMIX_host_get_state(h_simdata->host)==0) {
-               //t_simdata->comm = NULL;
-               SIMIX_action_destroy(t_simdata->comm);
-               t_simdata->comm = NULL;
+  } else if (SIMIX_host_get_state(SIMIX_host_self()) == 0) {
+    /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
+    SIMIX_action_destroy(task->simdata->compute);
+    simdata->comm = NULL;
+    simdata->compute = NULL;
     MSG_RETURN(MSG_HOST_FAILURE);
-  } else { 
-               //t_simdata->comm = NULL;
-               SIMIX_action_destroy(t_simdata->comm);
-               t_simdata->comm = NULL;
-    MSG_RETURN(MSG_TRANSFER_FAILURE);
+  } else {
+    /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
+    SIMIX_action_destroy(task->simdata->compute);
+    simdata->comm = NULL;
+    simdata->compute = NULL;
+    MSG_RETURN(MSG_TASK_CANCELLED);
   }
 
 }
-       
+
+
 /** \ingroup msg_gos_functions
- * \brief Listen on a channel and wait for receiving a task.
+ * \brief Sleep for the specified number of seconds
  *
- * It takes two parameters.
+ * Makes the current process sleep until \a time seconds have elapsed.
+ *
+ * \param nb_sec a number of second
+ */
+MSG_error_t MSG_process_sleep(double nb_sec)
+{
+  smx_action_t act_sleep;
+  m_process_t proc = MSG_process_self();
+  e_surf_action_state_t state = SURF_ACTION_NOT_IN_THE_SYSTEM;
+  smx_mutex_t mutex;
+  smx_cond_t cond;
+
+  /* create action to sleep */
+  act_sleep =
+    SIMIX_action_sleep(SIMIX_process_get_host(proc->simdata->s_process),
+                       nb_sec);
+
+  mutex = SIMIX_mutex_init();
+  SIMIX_mutex_lock(mutex);
+
+  /* create conditional and register action to it */
+  cond = SIMIX_cond_init();
+
+  proc->simdata->waiting_action = act_sleep;
+  SIMIX_register_action_to_condition(act_sleep, cond);
+  do {
+    SIMIX_cond_wait(cond, mutex);
+    state = SIMIX_action_get_state(act_sleep);
+  } while (state == SURF_ACTION_READY || state == SURF_ACTION_RUNNING);
+  proc->simdata->waiting_action = NULL;
+  SIMIX_unregister_action_to_condition(act_sleep, cond);
+  SIMIX_mutex_unlock(mutex);
+
+  /* remove variables */
+  SIMIX_cond_destroy(cond);
+  SIMIX_mutex_destroy(mutex);
+
+  if (SIMIX_action_get_state(act_sleep) == SURF_ACTION_DONE) {
+    if (SIMIX_host_get_state(SIMIX_host_self()) == SURF_RESOURCE_OFF) {
+      SIMIX_action_destroy(act_sleep);
+      MSG_RETURN(MSG_HOST_FAILURE);
+    }
+  } else {
+    SIMIX_action_destroy(act_sleep);
+    MSG_RETURN(MSG_HOST_FAILURE);
+  }
+
+  SIMIX_action_destroy(act_sleep);
+  MSG_RETURN(MSG_OK);
+}
+
+/** \ingroup msg_gos_functions
+ * \brief Listen on \a channel and waits for receiving a task from \a host.
+ *
+ * It takes three parameters.
  * \param task a memory location for storing a #m_task_t. It will
    hold a task when this function will return. Thus \a task should not
    be equal to \c NULL and \a *task should be equal to \c NULL. If one of
@@ -161,19 +278,20 @@ static MSG_error_t __MSG_task_get_with_time_out_from_host(m_task_t * task,
  * \param channel the channel on which the agent should be
    listening. This value has to be >=0 and < than the maximal
    number of channels fixed with MSG_set_channel_number().
+ * \param host the host that is to be watched.
  * \return #MSG_FATAL if \a task is equal to \c NULL, #MSG_WARNING
* if \a *task is not equal to \c NULL, and #MSG_OK otherwise.
  if \a *task is not equal to \c NULL, and #MSG_OK otherwise.
  */
-MSG_error_t MSG_task_get(m_task_t * task,
-                        m_channel_t channel)
+MSG_error_t
+MSG_task_get_from_host(m_task_t * task, m_channel_t channel, m_host_t host)
 {
-  return MSG_task_get_with_time_out(task, channel, -1);
+  return MSG_task_get_ext(task, channel, -1, host);
 }
 
 /** \ingroup msg_gos_functions
- * \brief Listen on a channel and wait for receiving a task with a timeout.
+ * \brief Listen on a channel and wait for receiving a task.
  *
- * It takes three parameters.
+ * It takes two parameters.
  * \param task a memory location for storing a #m_task_t. It will
    hold a task when this function will return. Thus \a task should not
    be equal to \c NULL and \a *task should be equal to \c NULL. If one of
@@ -181,22 +299,16 @@ MSG_error_t MSG_task_get(m_task_t * task,
  * \param channel the channel on which the agent should be
    listening. This value has to be >=0 and < than the maximal
    number of channels fixed with MSG_set_channel_number().
- * \param max_duration the maximum time to wait for a task before giving
-    up. In such a case, #MSG_TRANSFER_FAILURE will be returned, \a task 
-    will not be modified and will still be
-    equal to \c NULL when returning. 
  * \return #MSG_FATAL if \a task is equal to \c NULL, #MSG_WARNING
  if \a *task is not equal to \c NULL, and #MSG_OK otherwise.
* if \a *task is not equal to \c NULL, and #MSG_OK otherwise.
  */
-MSG_error_t MSG_task_get_with_time_out(m_task_t * task,
-                                      m_channel_t channel,
-                                      double max_duration)
+MSG_error_t MSG_task_get(m_task_t * task, m_channel_t channel)
 {
-  return __MSG_task_get_with_time_out_from_host(task, channel, max_duration, NULL);
+  return MSG_task_get_with_timeout(task, channel, -1);
 }
 
 /** \ingroup msg_gos_functions
- * \brief Listen on \a channel and waits for receiving a task from \a host.
+ * \brief Listen on a channel and wait for receiving a task with a timeout.
  *
  * It takes three parameters.
  * \param task a memory location for storing a #m_task_t. It will
@@ -206,173 +318,108 @@ MSG_error_t MSG_task_get_with_time_out(m_task_t * task,
  * \param channel the channel on which the agent should be
    listening. This value has to be >=0 and < than the maximal
    number of channels fixed with MSG_set_channel_number().
- * \param host the host that is to be watched.
+ * \param max_duration the maximum time to wait for a task before giving
+    up. In such a case, #MSG_TRANSFER_FAILURE will be returned, \a task
+    will not be modified and will still be
+    equal to \c NULL when returning.
  * \return #MSG_FATAL if \a task is equal to \c NULL, #MSG_WARNING
    if \a *task is not equal to \c NULL, and #MSG_OK otherwise.
  */
-MSG_error_t MSG_task_get_from_host(m_task_t * task, int channel, 
-                                  m_host_t host)
+MSG_error_t
+MSG_task_get_with_timeout(m_task_t * task, m_channel_t channel,
+                          double max_duration)
 {
-  return __MSG_task_get_with_time_out_from_host(task, channel, -1, host);
+  return MSG_task_get_ext(task, channel, max_duration, NULL);
 }
 
-/** \ingroup msg_gos_functions
- * \brief Test whether there is a pending communication on a channel.
- *
- * It takes one parameter.
- * \param channel the channel on which the agent should be
-   listening. This value has to be >=0 and < than the maximal
-   number of channels fixed with MSG_set_channel_number().
- * \return 1 if there is a pending communication and 0 otherwise
+/** \defgroup msg_gos_functions MSG Operating System Functions
+ *  \brief This section describes the functions that can be used
+ *  by an agent for handling some task.
  */
-int MSG_task_Iprobe(m_channel_t channel)
-{
-  m_host_t h = NULL;
-
-  xbt_assert1((channel>=0) && (channel < msg_global->max_channel),"Invalid channel %d",channel);
-  CHECK_HOST();
 
-  DEBUG2("Probing on channel %d (%s)", channel,h->name);
+MSG_error_t
+MSG_task_get_ext(m_task_t * task, m_channel_t channel, double timeout,
+                 m_host_t host)
+{
+  xbt_assert1((channel >= 0)
+              && (channel < msg_global->max_channel), "Invalid channel %d",
+              channel);
 
-  h = MSG_host_self();
-  return(xbt_fifo_get_first_item(h->simdata->mbox[channel])!=NULL);
+  return
+    MSG_mailbox_get_task_ext(MSG_mailbox_get_by_channel
+                             (MSG_host_self(), channel), task, host, timeout);
 }
 
-/** \ingroup msg_gos_functions
- * \brief Test whether there is a pending communication on a channel, and who sent it.
- *
- * It takes one parameter.
- * \param channel the channel on which the agent should be
-   listening. This value has to be >=0 and < than the maximal
-   number of channels fixed with MSG_set_channel_number().
- * \return -1 if there is no pending communication and the PID of the process who sent it otherwise
- */
-int MSG_task_probe_from(m_channel_t channel)
+MSG_error_t
+MSG_task_receive_from_host(m_task_t * task, const char *alias, m_host_t host)
 {
-  m_host_t h = NULL;
-  xbt_fifo_item_t item;
-  m_task_t t;
+  return MSG_task_receive_ext(task, alias, -1, host);
+}
 
-  xbt_assert1((channel>=0) && (channel < msg_global->max_channel),"Invalid channel %d",channel);
-  CHECK_HOST();
+MSG_error_t MSG_task_receive(m_task_t * task, const char *alias)
+{
+  return MSG_task_receive_with_timeout(task, alias, -1);
+}
 
-  h = MSG_host_self();
+MSG_error_t
+MSG_task_receive_with_timeout(m_task_t * task, const char *alias,
+                              double timeout)
+{
+  return MSG_task_receive_ext(task, alias, timeout, NULL);
+}
 
-  DEBUG2("Probing on channel %d (%s)", channel,h->name);
-   
-  item = xbt_fifo_get_first_item(h->simdata->mbox[channel]);
-  if ( (!item) || (!(t = xbt_fifo_get_item_content(item))) )
-    return -1;
-   
-  return MSG_process_get_PID(t->simdata->sender);
+MSG_error_t
+MSG_task_receive_ext(m_task_t * task, const char *alias, double timeout,
+                     m_host_t host)
+{
+  return MSG_mailbox_get_task_ext(MSG_mailbox_get_by_alias(alias), task, host,
+                                  timeout);
 }
 
+
 /** \ingroup msg_gos_functions
- * \brief Wait for at most \a max_duration second for a task reception
-   on \a channel. *\a PID is updated with the PID of the first process
-   that triggered this event if any.
+ * \brief Put a task on a channel of an host and waits for the end of the
+ * transmission.
  *
- * It takes three parameters:
- * \param channel the channel on which the agent should be
-   listening. This value has to be >=0 and < than the maximal.
-   number of channels fixed with MSG_set_channel_number().
- * \param PID a memory location for storing an int.
- * \param max_duration the maximum time to wait for a task before
-    giving up. In the case of a reception, *\a PID will be updated
-    with the PID of the first process to send a task.
- * \return #MSG_HOST_FAILURE if the host is shut down in the meantime
-   and #MSG_OK otherwise.
+ * This function is used for describing the behavior of an agent. It
+ * takes three parameter.
+ * \param task a #m_task_t to send on another location. This task
+   will not be usable anymore when the function will return. There is
+   no automatic task duplication and you have to save your parameters
+   before calling this function. Tasks are unique and once it has been
+   sent to another location, you should not access it anymore. You do
+   not need to call MSG_task_destroy() but to avoid using, as an
+   effect of inattention, this task anymore, you definitely should
+   renitialize it with #MSG_TASK_UNINITIALIZED. Note that this task
+   can be transfered iff it has been correctly created with
+   MSG_task_create().
+ * \param dest the destination of the message
+ * \param channel the channel on which the agent should put this
+   task. This value has to be >=0 and < than the maximal number of
+   channels fixed with MSG_set_channel_number().
+ * \return #MSG_FATAL if \a task is not properly initialized and
+ * #MSG_OK otherwise. Returns #MSG_HOST_FAILURE if the host on which
+ * this function was called was shut down. Returns
+ * #MSG_TRANSFER_FAILURE if the transfer could not be properly done
+ * (network failure, dest failure)
  */
-MSG_error_t MSG_channel_select_from(m_channel_t channel, double max_duration,
-               int *PID)
+MSG_error_t MSG_task_put(m_task_t task, m_host_t dest, m_channel_t channel)
 {
-       m_host_t h = NULL;
-       simdata_host_t h_simdata = NULL;
-       xbt_fifo_item_t item;
-       m_task_t t;
-       int first_time = 1;
-       smx_cond_t cond;
-
-       xbt_assert1((channel>=0) && (channel < msg_global->max_channel),"Invalid channel %d",channel);
-       if(PID) {
-               *PID = -1;
-       }
-
-       if(max_duration==0.0) {
-               *PID = MSG_task_probe_from(channel);
-               MSG_RETURN(MSG_OK);
-       } else {
-               CHECK_HOST();
-               h = MSG_host_self();
-               h_simdata = h->simdata;
-
-               DEBUG2("Probing on channel %d (%s)", channel,h->name);
-               while(!(item = xbt_fifo_get_first_item(h->simdata->mbox[channel]))) {
-                       if(max_duration>0) {
-                               if(!first_time) {
-                                       MSG_RETURN(MSG_OK);
-                               }
-                       }
-                       SIMIX_mutex_lock(h_simdata->mutex);
-                       xbt_assert1(!(h_simdata->sleeping[channel]),
-                                       "A process is already blocked on this channel %d", channel);
-                       cond = SIMIX_cond_init();
-                       h_simdata->sleeping[channel] = cond; /* I'm waiting. Wake me up when you're ready */
-                       if(max_duration>0) {
-                               SIMIX_cond_wait_timeout(cond,h_simdata->mutex, max_duration);
-                       } else {
-                               SIMIX_cond_wait(cond,h_simdata->mutex);
-                       }
-                       SIMIX_cond_destroy(cond);
-                       SIMIX_mutex_unlock(h_simdata->mutex);
-                       if(SIMIX_host_get_state(h_simdata->host)==0) {
-                               MSG_RETURN(MSG_HOST_FAILURE);
-                       }
-                       h_simdata->sleeping[channel] = NULL;
-                       first_time = 0;
-               }
-               if (!item || !(t = xbt_fifo_get_item_content(item))) {
-                       MSG_RETURN(MSG_OK);
-               }
-               if(PID) {
-                       *PID = MSG_process_get_PID(t->simdata->sender);
-               }
-               MSG_RETURN(MSG_OK);
-       }
+  return MSG_task_put_with_timeout(task, dest, channel, -1.0);
 }
 
-
 /** \ingroup msg_gos_functions
-
- * \brief Return the number of tasks waiting to be received on a \a
-   channel and sent by \a host.
+ * \brief Does exactly the same as MSG_task_put but with a bounded transmition
+ * rate.
  *
- * It takes two parameters.
- * \param channel the channel on which the agent should be
-   listening. This value has to be >=0 and < than the maximal
-   number of channels fixed with MSG_set_channel_number().
- * \param host the host that is to be watched.
- * \return the number of tasks waiting to be received on \a channel
-   and sent by \a host.
+ * \sa MSG_task_put
  */
-int MSG_task_probe_from_host(int channel, m_host_t host)
+MSG_error_t
+MSG_task_put_bounded(m_task_t task, m_host_t dest, m_channel_t channel,
+                     double maxrate)
 {
-  xbt_fifo_item_t item;
-  m_task_t t;
-  int count = 0;
-  m_host_t h = NULL;
-  
-  xbt_assert1((channel>=0) && (channel < msg_global->max_channel),"Invalid channel %d",channel);
-  CHECK_HOST();
-  h = MSG_host_self();
-
-  DEBUG2("Probing on channel %d (%s)", channel,h->name);
-   
-  xbt_fifo_foreach(h->simdata->mbox[channel],item,t,m_task_t) {
-    if(t->simdata->source==host) count++;
-  }
-   
-  return count;
+  task->simdata->rate = maxrate;
+  return MSG_task_put(task, dest, channel);
 }
 
 /** \ingroup msg_gos_functions \brief Put a task on a channel of an
@@ -395,379 +442,312 @@ int MSG_task_probe_from_host(int channel, m_host_t host)
  * \param channel the channel on which the agent should put this
    task. This value has to be >=0 and < than the maximal number of
    channels fixed with MSG_set_channel_number().
- * \param max_duration the maximum time to wait for a task before giving
-    up. In such a case, #MSG_TRANSFER_FAILURE will be returned, \a task 
-    will not be modified 
+ * \param timeout the maximum time to wait for a task before giving
+    up. In such a case, #MSG_TRANSFER_FAILURE will be returned, \a task
+    will not be modified
  * \return #MSG_FATAL if \a task is not properly initialized and
    #MSG_OK otherwise. Returns #MSG_HOST_FAILURE if the host on which
    this function was called was shut down. Returns
    #MSG_TRANSFER_FAILURE if the transfer could not be properly done
    (network failure, dest failure, timeout...)
  */
-MSG_error_t MSG_task_put_with_timeout(m_task_t task, m_host_t dest, 
-                                     m_channel_t channel, double max_duration)
+MSG_error_t
+MSG_task_put_with_timeout(m_task_t task, m_host_t dest, m_channel_t channel,
+                          double timeout)
+{
+  xbt_assert1((channel >= 0)
+              && (channel < msg_global->max_channel), "Invalid channel %d",
+              channel);
+
+  return
+    MSG_mailbox_put_with_timeout(MSG_mailbox_get_by_channel(dest, channel),
+                                 task, timeout);
+}
+
+MSG_error_t MSG_task_send(m_task_t task, const char *alias)
+{
+  return MSG_task_send_with_timeout(task, alias, -1);
+}
+
+
+MSG_error_t
+MSG_task_send_bounded(m_task_t task, const char *alias, double maxrate)
 {
+  task->simdata->rate = maxrate;
+  return MSG_task_send(task, alias);
+}
 
 
-  m_process_t process = MSG_process_self();
-  simdata_task_t task_simdata = NULL;
-  m_host_t local_host = NULL;
-  m_host_t remote_host = NULL;
+MSG_error_t
+MSG_task_send_with_timeout(m_task_t task, const char *alias, double timeout)
+{
+  return MSG_mailbox_put_with_timeout(MSG_mailbox_get_by_alias(alias), task,
+                                      timeout);
+}
+
+int MSG_task_listen(const char *alias)
+{
   CHECK_HOST();
 
-  xbt_assert1((channel>=0) && (channel < msg_global->max_channel),"Invalid channel %d",channel);
-
-  task_simdata = task->simdata;
-  task_simdata->sender = process;
-  task_simdata->source = MSG_process_get_host(process);
-  xbt_assert0(task_simdata->using==1,
-             "This task is still being used somewhere else. You cannot send it now. Go fix your code!");
-  task_simdata->comm = NULL;
-  
-  local_host = ((simdata_process_t) process->simdata)->host;
-  remote_host = dest;
-
-  DEBUG4("Trying to send a task (%g kB) from %s to %s on channel %d", 
-        task->simdata->message_size/1000,local_host->name, remote_host->name, channel);
-
-       SIMIX_mutex_lock(remote_host->simdata->mutex);
-  xbt_fifo_push(((simdata_host_t) remote_host->simdata)->
-               mbox[channel], task);
-
-  
-  if(remote_host->simdata->sleeping[channel]) {
-    DEBUG0("Somebody is listening. Let's wake him up!");
-               SIMIX_cond_signal(remote_host->simdata->sleeping[channel]);
-  }
-       SIMIX_mutex_unlock(remote_host->simdata->mutex);
-
-  process->simdata->put_host = dest;
-  process->simdata->put_channel = channel;
-       SIMIX_mutex_lock(task->simdata->mutex);
- // DEBUG4("Task sent (%g kB) from %s to %s on channel %d, waiting...", task->simdata->message_size/1000,local_host->name, remote_host->name, channel);
-
-       process->simdata->waiting_task = task;
-       if (max_duration >0) {
-               SIMIX_cond_wait_timeout(task->simdata->cond,task->simdata->mutex,max_duration);
-               /* verify if the timeout happened and the communication didn't started yet */
-               if (task->simdata->comm==NULL) {
-                       task->simdata->using--;
-                       process->simdata->waiting_task = NULL;
-                       xbt_fifo_remove(((simdata_host_t) remote_host->simdata)->mbox[channel],
-                       task);
-                       if (task->simdata->receiver) {
-                               task->simdata->receiver->simdata->waiting_task = NULL;
-                       }
-                       task->simdata->sender = NULL;
-                       SIMIX_mutex_unlock(task->simdata->mutex);
-                       MSG_RETURN(MSG_TRANSFER_FAILURE);
-               }
-       }
-       else {
-               SIMIX_cond_wait(task->simdata->cond,task->simdata->mutex);
-       }
-
-       DEBUG1("Action terminated %s",task->name);    
-       task->simdata->using--;
-       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;
-               /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
-       //      task->simdata->comm = NULL;
-               //task->simdata->compute = NULL;
-       }
-       task->simdata->sender = NULL;
-       SIMIX_mutex_unlock(task->simdata->mutex);
-
-       if(SIMIX_action_get_state(task->simdata->comm) == SURF_ACTION_DONE) {
-    MSG_RETURN(MSG_OK);
-       } else if (SIMIX_host_get_state(local_host->simdata->host)==0) {
-    MSG_RETURN(MSG_HOST_FAILURE);
-  } else { 
-    MSG_RETURN(MSG_TRANSFER_FAILURE);
-  }
+  return !MSG_mailbox_is_empty(MSG_mailbox_get_by_alias(alias));
 }
 
 /** \ingroup msg_gos_functions
- * \brief Put a task on a channel of an host and waits for the end of the
- * transmission.
+ * \brief Test whether there is a pending communication on a channel.
  *
- * This function is used for describing the behavior of an agent. It
- * takes three parameter.
- * \param task a #m_task_t to send on another location. This task
-   will not be usable anymore when the function will return. There is
-   no automatic task duplication and you have to save your parameters
-   before calling this function. Tasks are unique and once it has been
-   sent to another location, you should not access it anymore. You do
-   not need to call MSG_task_destroy() but to avoid using, as an
-   effect of inattention, this task anymore, you definitely should
-   renitialize it with #MSG_TASK_UNINITIALIZED. Note that this task
-   can be transfered iff it has been correctly created with
-   MSG_task_create().
- * \param dest the destination of the message
- * \param channel the channel on which the agent should put this
-   task. This value has to be >=0 and < than the maximal number of
-   channels fixed with MSG_set_channel_number().
- * \return #MSG_FATAL if \a task is not properly initialized and
- * #MSG_OK otherwise. Returns #MSG_HOST_FAILURE if the host on which
- * this function was called was shut down. Returns
- * #MSG_TRANSFER_FAILURE if the transfer could not be properly done
- * (network failure, dest failure)
+ * It takes one parameter.
+ * \param channel the channel on which the agent should be
+   listening. This value has to be >=0 and < than the maximal
+   number of channels fixed with MSG_set_channel_number().
+ * \return 1 if there is a pending communication and 0 otherwise
  */
-MSG_error_t MSG_task_put(m_task_t task,
-                        m_host_t dest, m_channel_t channel)
+int MSG_task_Iprobe(m_channel_t channel)
 {
-  return MSG_task_put_with_timeout(task, dest, channel, -1.0);
+  xbt_assert1((channel >= 0)
+              && (channel < msg_global->max_channel), "Invalid channel %d",
+              channel);
+
+  CHECK_HOST();
+
+  return
+    !MSG_mailbox_is_empty(MSG_mailbox_get_by_channel
+                          (MSG_host_self(), channel));
 }
 
 /** \ingroup msg_gos_functions
- * \brief Does exactly the same as MSG_task_put but with a bounded transmition 
- * rate.
+
+ * \brief Return the number of tasks waiting to be received on a \a
+   channel and sent by \a host.
  *
- * \sa MSG_task_put
+ * It takes two parameters.
+ * \param channel the channel on which the agent should be
+   listening. This value has to be >=0 and < than the maximal
+   number of channels fixed with MSG_set_channel_number().
+ * \param host the host that is to be watched.
+ * \return the number of tasks waiting to be received on \a channel
+   and sent by \a host.
  */
-MSG_error_t MSG_task_put_bounded(m_task_t task,
-                                m_host_t dest, m_channel_t channel,
-                                double max_rate)
+int MSG_task_probe_from_host(int channel, m_host_t host)
 {
-  MSG_error_t res = MSG_OK;
-  task->simdata->rate=max_rate;
-  res = MSG_task_put(task, dest, channel);
-  return(res);
+  xbt_assert1((channel >= 0)
+              && (channel < msg_global->max_channel), "Invalid channel %d",
+              channel);
+
+  CHECK_HOST();
+
+  return
+    MSG_mailbox_get_count_host_waiting_tasks(MSG_mailbox_get_by_channel
+                                             (MSG_host_self(), channel),
+                                             host);
+
+}
+
+int MSG_task_listen_from_host(const char *alias, m_host_t host)
+{
+  CHECK_HOST();
+
+  return
+    MSG_mailbox_get_count_host_waiting_tasks(MSG_mailbox_get_by_alias(alias),
+                                             host);
 }
 
 /** \ingroup msg_gos_functions
- * \brief Executes a task and waits for its termination.
+ * \brief Test whether there is a pending communication on a channel, and who sent it.
  *
- * This function is used for describing the behavior of an agent. It
- * takes only one parameter.
- * \param task a #m_task_t to execute on the location on which the
-   agent is running.
- * \return #MSG_FATAL if \a task is not properly initialized and
- * #MSG_OK otherwise.
+ * It takes one parameter.
+ * \param channel the channel on which the agent should be
+   listening. This value has to be >=0 and < than the maximal
+   number of channels fixed with MSG_set_channel_number().
+ * \return -1 if there is no pending communication and the PID of the process who sent it otherwise
  */
-MSG_error_t MSG_task_execute(m_task_t task)
+int MSG_task_probe_from(m_channel_t channel)
 {
-       simdata_task_t simdata = NULL;
-       m_process_t self = MSG_process_self();
+  m_task_t task;
+
   CHECK_HOST();
 
-  simdata = task->simdata;
-  xbt_assert0((!simdata->compute)&&(task->simdata->using==1),
-             "This task is executed somewhere else. Go fix your code!");
-       
-       DEBUG1("Computing on %s", MSG_process_self()->simdata->host->name);
-  simdata->using++;
-       SIMIX_mutex_lock(simdata->mutex);
-  simdata->compute = SIMIX_action_execute(SIMIX_host_self(), task->name, simdata->computation_amount);
-       SIMIX_action_set_priority(simdata->compute, simdata->priority);
-
-       self->simdata->waiting_task = task;
-       SIMIX_register_action_to_condition(simdata->compute, simdata->cond);
-       SIMIX_register_condition_to_action(simdata->compute, simdata->cond);
-       SIMIX_cond_wait(simdata->cond, simdata->mutex);
-       self->simdata->waiting_task = NULL;
-
-       SIMIX_mutex_unlock(simdata->mutex);
-  simdata->using--;
-
-       if(SIMIX_action_get_state(task->simdata->compute) == SURF_ACTION_DONE) {
-               /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
-               SIMIX_action_destroy(task->simdata->compute);
-               simdata->computation_amount = 0.0;
-               simdata->comm = NULL;
-               simdata->compute = NULL;
-    MSG_RETURN(MSG_OK);
-       } else if (SIMIX_host_get_state(SIMIX_host_self())==0) {
-               /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
-               SIMIX_action_destroy(task->simdata->compute);
-               simdata->comm = NULL;
-               simdata->compute = NULL;
-    MSG_RETURN(MSG_HOST_FAILURE);
-  } else { 
-               /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
-               SIMIX_action_destroy(task->simdata->compute);
-               simdata->comm = NULL;
-               simdata->compute = NULL;
-    MSG_RETURN(MSG_TASK_CANCELLED);
-  }
+  xbt_assert1((channel >= 0)
+              && (channel < msg_global->max_channel), "Invalid channel %d",
+              channel);
+
+  if (NULL ==
+      (task =
+       MSG_mailbox_get_head(MSG_mailbox_get_by_channel
+                            (MSG_host_self(), channel))))
+    return -1;
+
+  return MSG_process_get_PID(task->simdata->sender);
 }
 
+int MSG_task_listen_from(const char *alias)
+{
+  m_task_t task;
 
-/** \ingroup m_task_management
- * \brief Creates a new #m_task_t (a parallel one....).
+  CHECK_HOST();
+
+  if (NULL == (task = MSG_mailbox_get_head(MSG_mailbox_get_by_alias(alias))))
+    return -1;
+
+  return MSG_process_get_PID(task->simdata->sender);
+}
+
+/** \ingroup msg_gos_functions
+ * \brief Wait for at most \a max_duration second for a task reception
+   on \a channel.
+
+ * \a PID is updated with the PID of the first process that triggered this event if any.
  *
- * A constructor for #m_task_t taking six arguments and returning the 
-   corresponding object.
- * \param name a name for the object. It is for user-level information
-   and can be NULL.
- * \param host_nb the number of hosts implied in the parallel task.
- * \param host_list an array of \p host_nb m_host_t.
- * \param computation_amount an array of \p host_nb
-   doubles. computation_amount[i] is the total number of operations
-   that have to be performed on host_list[i].
- * \param communication_amount an array of \p host_nb* \p host_nb doubles.
- * \param data a pointer to any data may want to attach to the new
-   object.  It is for user-level information and can be NULL. It can
-   be retrieved with the function \ref MSG_task_get_data.
- * \see m_task_t
- * \return The new corresponding object.
+ * It takes three parameters:
+ * \param channel the channel on which the agent should be
+   listening. This value has to be >=0 and < than the maximal.
+   number of channels fixed with MSG_set_channel_number().
+ * \param PID a memory location for storing an int.
+ * \param timeout the maximum time to wait for a task before
+    giving up. In the case of a reception, *\a PID will be updated
+    with the PID of the first process to send a task.
+ * \return #MSG_HOST_FAILURE if the host is shut down in the meantime
+   and #MSG_OK otherwise.
  */
-m_task_t MSG_parallel_task_create(const char *name, 
-                                 int host_nb,
-                                 const m_host_t *host_list,
-                                 double *computation_amount,
-                                 double *communication_amount,
-                                 void *data)
+MSG_error_t
+MSG_channel_select_from(m_channel_t channel, double timeout, int *PID)
 {
-  int i;
-  simdata_task_t simdata = xbt_new0(s_simdata_task_t,1);
-  m_task_t task = xbt_new0(s_m_task_t,1);
-  task->simdata = simdata;
+  m_host_t h = NULL;
+  simdata_host_t h_simdata = NULL;
+  m_task_t t;
+  int first_time = 1;
+  smx_cond_t cond;
+  msg_mailbox_t mailbox;
 
-  /* Task structure */
-  task->name = xbt_strdup(name);
-  task->data = data;
+  xbt_assert1((channel >= 0)
+              && (channel < msg_global->max_channel), "Invalid channel %d",
+              channel);
 
-  /* Simulator Data */
-  simdata->computation_amount = 0;
-  simdata->message_size = 0;
-       simdata->cond = SIMIX_cond_init();
-       simdata->mutex = SIMIX_mutex_init();
-       simdata->compute = NULL;
-       simdata->comm = NULL;
-  simdata->rate = -1.0;
-  simdata->using = 1;
-  simdata->sender = NULL;
-  simdata->receiver = NULL;
-  simdata->source = NULL;
+  if (PID) {
+    *PID = -1;
+  }
 
-  simdata->host_nb = host_nb;
-  simdata->host_list = xbt_new0(void *, host_nb);
-  simdata->comp_amount = computation_amount;
-  simdata->comm_amount = communication_amount;
+  if (timeout == 0.0) {
+    *PID = MSG_task_probe_from(channel);
+    MSG_RETURN(MSG_OK);
+  } else {
+    CHECK_HOST();
+    h = MSG_host_self();
+    h_simdata = h->simdata;
 
-  for(i=0;i<host_nb;i++)
-    simdata->host_list[i] = host_list[i]->simdata->host;
+    mailbox = MSG_mailbox_get_by_channel(MSG_host_self(), channel);
 
-  return task;
+    while (MSG_mailbox_is_empty(mailbox)) {
+      if (timeout > 0) {
+        if (!first_time) {
+          MSG_RETURN(MSG_OK);
+        }
+      }
+
+      SIMIX_mutex_lock(h_simdata->mutex);
+
+      xbt_assert1(!MSG_mailbox_get_cond(mailbox),
+                  "A process is already blocked on this channel %d", channel);
 
+      cond = SIMIX_cond_init();
+
+      MSG_mailbox_set_cond(mailbox, cond);
+
+      if (timeout > 0) {
+        SIMIX_cond_wait_timeout(cond, h_simdata->mutex, timeout);
+      } else {
+        SIMIX_cond_wait(cond, h_simdata->mutex);
+      }
+
+      SIMIX_cond_destroy(cond);
+      SIMIX_mutex_unlock(h_simdata->mutex);
+
+      if (SIMIX_host_get_state(h_simdata->smx_host) == 0) {
+        MSG_RETURN(MSG_HOST_FAILURE);
+      }
+
+      MSG_mailbox_set_cond(mailbox, NULL);
+      first_time = 0;
+    }
+
+    if (NULL == (t = MSG_mailbox_get_head(mailbox)))
+      MSG_RETURN(MSG_OK);
+
+
+    if (PID) {
+      *PID = MSG_process_get_PID(t->simdata->sender);
+    }
+
+    MSG_RETURN(MSG_OK);
+  }
 }
 
 
-MSG_error_t MSG_parallel_task_execute(m_task_t task)
+MSG_error_t MSG_alias_select_from(const char *alias, double timeout, int *PID)
 {
-       simdata_task_t simdata = NULL;
-       m_process_t self = MSG_process_self();
-  CHECK_HOST();
+  m_host_t h = NULL;
+  simdata_host_t h_simdata = NULL;
+  m_task_t t;
+  int first_time = 1;
+  smx_cond_t cond;
+  msg_mailbox_t mailbox;
 
-  simdata = task->simdata;
-  xbt_assert0((!simdata->compute)&&(task->simdata->using==1),
-             "This task is executed somewhere else. Go fix your code!");
-
-  xbt_assert0(simdata->host_nb,"This is not a parallel task. Go to hell.");
-       
-       DEBUG1("Computing on %s", MSG_process_self()->simdata->host->name);
-  simdata->using++;
-       SIMIX_mutex_lock(simdata->mutex);
-  simdata->compute = SIMIX_action_parallel_execute(task->name, simdata->host_nb, simdata->host_list, simdata->comp_amount, simdata->comm_amount, 1.0, -1.0);
-
-       self->simdata->waiting_task = task;
-       SIMIX_register_action_to_condition(simdata->compute, simdata->cond);
-       SIMIX_register_condition_to_action(simdata->compute, simdata->cond);
-       SIMIX_cond_wait(simdata->cond, simdata->mutex);
-       self->simdata->waiting_task = NULL;
-
-
-       SIMIX_mutex_unlock(simdata->mutex);
-  simdata->using--;
-
-       if(SIMIX_action_get_state(task->simdata->compute) == SURF_ACTION_DONE) {
-               /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
-               SIMIX_action_destroy(task->simdata->compute);
-               simdata->computation_amount = 0.0;
-               simdata->comm = NULL;
-               simdata->compute = NULL;
+  if (PID) {
+    *PID = -1;
+  }
+
+  if (timeout == 0.0) {
+    *PID = MSG_task_listen_from(alias);
     MSG_RETURN(MSG_OK);
-       } else if (SIMIX_host_get_state(SIMIX_host_self())==0) {
-               /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
-               SIMIX_action_destroy(task->simdata->compute);
-               simdata->comm = NULL;
-               simdata->compute = NULL;
-    MSG_RETURN(MSG_HOST_FAILURE);
-  } else { 
-               /* action ended, set comm and compute = NULL, the actions is already destroyed in the main function */
-               SIMIX_action_destroy(task->simdata->compute);
-               simdata->comm = NULL;
-               simdata->compute = NULL;
-    MSG_RETURN(MSG_TASK_CANCELLED);
-  }    
+  } else {
+    CHECK_HOST();
+    h = MSG_host_self();
+    h_simdata = h->simdata;
 
-}
+    DEBUG2("Probing on alias %s (%s)", alias, h->name);
 
+    mailbox = MSG_mailbox_get_by_alias(alias);
 
-/** \ingroup msg_gos_functions
- * \brief Sleep for the specified number of seconds
- *
- * Makes the current process sleep until \a time seconds have elapsed.
- *
- * \param nb_sec a number of second
- */
-MSG_error_t MSG_process_sleep(double nb_sec)
-{
-       smx_action_t act_sleep;
-       m_process_t proc = MSG_process_self();
-       smx_mutex_t mutex;
-       smx_cond_t cond;
-       /* create action to sleep */
-       act_sleep = SIMIX_action_sleep(SIMIX_process_get_host(proc->simdata->smx_process),nb_sec);
-       
-       mutex = SIMIX_mutex_init();
-       SIMIX_mutex_lock(mutex);
-       /* create conditional and register action to it */
-       cond = SIMIX_cond_init();
-
-       SIMIX_register_condition_to_action(act_sleep, cond);
-       SIMIX_register_action_to_condition(act_sleep, cond);
-       SIMIX_cond_wait(cond,mutex);
-       SIMIX_mutex_unlock(mutex);
-
-       /* remove variables */
-       SIMIX_cond_destroy(cond);
-       SIMIX_mutex_destroy(mutex);
-
-  if(SIMIX_action_get_state(act_sleep) == SURF_ACTION_DONE) {
-    if(SIMIX_host_get_state(SIMIX_host_self()) == SURF_CPU_OFF) {
-                       SIMIX_action_destroy(act_sleep);
-      MSG_RETURN(MSG_HOST_FAILURE);
+    while (MSG_mailbox_is_empty(mailbox)) {
+      if (timeout > 0) {
+        if (!first_time) {
+          MSG_RETURN(MSG_OK);
+        }
+      }
+
+      SIMIX_mutex_lock(h_simdata->mutex);
+
+      xbt_assert1(!MSG_mailbox_get_cond(mailbox),
+                  "A process is already blocked on this alias %s", alias);
+
+      cond = SIMIX_cond_init();
+
+      MSG_mailbox_set_cond(mailbox, cond);
+
+      if (timeout > 0) {
+        SIMIX_cond_wait_timeout(cond, h_simdata->mutex, timeout);
+      } else {
+        SIMIX_cond_wait(cond, h_simdata->mutex);
+      }
+
+      SIMIX_cond_destroy(cond);
+      SIMIX_mutex_unlock(h_simdata->mutex);
+
+      if (SIMIX_host_get_state(h_simdata->smx_host) == 0) {
+        MSG_RETURN(MSG_HOST_FAILURE);
+      }
+
+      MSG_mailbox_set_cond(mailbox, NULL);
+      first_time = 0;
     }
-  }
-       else {
-               SIMIX_action_destroy(act_sleep);
-               MSG_RETURN(MSG_HOST_FAILURE);
-       }
 
+    if (NULL == (t = MSG_mailbox_get_head(mailbox)))
+      MSG_RETURN(MSG_OK);
 
-       MSG_RETURN(MSG_OK);
-}
 
-/** \ingroup msg_gos_functions
- * \brief Return the number of MSG tasks currently running on
- * the host of the current running process.
- */
-static int MSG_get_msgload(void) 
-{
-       xbt_die("not implemented yet");
-       return 0;
-}
+    if (PID) {
+      *PID = MSG_process_get_PID(t->simdata->sender);
+    }
 
-/** \ingroup msg_gos_functions
- *
- * \brief Return the last value returned by a MSG function (except
- * MSG_get_errno...).
- */
-MSG_error_t MSG_get_errno(void)
-{
-  return PROCESS_GET_ERRNO();
+    MSG_RETURN(MSG_OK);
+  }
 }