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Bug fix in MSG raised by Matthieu and Henri!
[simgrid.git] / src / msg / gos.c
index ee4be29..ba0d5be 100644 (file)
 #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.
+/** \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();
+}
+
+/** \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();
+
+       simdata = task->simdata;
+       xbt_assert0((!simdata->compute) && (task->simdata->refcount  == 1),"This task is executed somewhere else. Go fix your code!");
+
+       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);
+
+       self->simdata->waiting_task = task;
+       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_task = 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;
+
+       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;
+}
 
-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)
+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();
 
-  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;
 
-  smx_cond_t cond = NULL;      //conditional wait if the task isn't on the channel yet
+       xbt_assert0((!simdata->compute) && (task->simdata->refcount  == 1),"This task is executed somewhere else. Go fix your code!");
 
-  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;
+       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_task = task;
+       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_task = 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);
        }
-       if (item) {
-         xbt_fifo_remove_item(h->simdata->mbox[channel], item);
-         break;
+       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);
        }
-      }
-    }
 
-    if (max_duration > 0) {
-      if (!first_time) {
-       SIMIX_mutex_unlock(h->simdata->mutex);
-       h_simdata->sleeping[channel] = NULL;
+}
+
+
+/** \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();
+       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();
+
+       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);
+       SIMIX_unregister_action_to_condition(act_sleep, cond);
+       SIMIX_mutex_unlock(mutex);
+
+       /* remove variables */
        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->s_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 */
-  /* create SIMIX action to the communication */
-  t_simdata->comm =
-      SIMIX_action_communicate(t_simdata->sender->simdata->m_host->
-                              simdata->s_host,
-                              process->simdata->m_host->simdata->s_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);
-       while (1) {
-               SIMIX_cond_wait(t_simdata->cond, t_simdata->mutex);
-               if (SIMIX_action_get_state(t_simdata->comm) != SURF_ACTION_RUNNING)
-                       break;
+       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);
+               }
+       }
+       else
+       {
+               SIMIX_action_destroy(act_sleep);
+               MSG_RETURN(MSG_HOST_FAILURE);
        }
-  SIMIX_unregister_action_to_condition(t_simdata->comm, t_simdata->cond);
-  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;
-               t_simdata->using--;
-    MSG_RETURN(MSG_OK);
-  } else if (SIMIX_host_get_state(h_simdata->s_host) == 0) {
-    //t_simdata->comm = NULL;
-    SIMIX_action_destroy(t_simdata->comm);
-    t_simdata->comm = NULL;
-               t_simdata->using--;
-    MSG_RETURN(MSG_HOST_FAILURE);
-  } else {
-    //t_simdata->comm = NULL;
-    SIMIX_action_destroy(t_simdata->comm);
-    t_simdata->comm = NULL;
-               t_simdata->using--;
-    MSG_RETURN(MSG_TRANSFER_FAILURE);
-  }
 
+       SIMIX_action_destroy(act_sleep);
+       MSG_RETURN(MSG_OK);
 }
 
 /** \ingroup msg_gos_functions
- * \brief Listen on a channel and wait for receiving a task.
+ * \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;
+}
+
+
+
+/** \ingroup msg_gos_functions
+ * \brief Listen on \a channel and waits for receiving a task from \a host.
  *
- * It takes two parameters.
+ * 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
@@ -178,18 +293,20 @@ 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
@@ -197,23 +314,17 @@ MSG_error_t MSG_task_get(m_task_t * task, m_channel_t channel)
  * \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
@@ -223,191 +334,63 @@ 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;
-
-  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);
-
-  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);
+       return MSG_task_receive_ext(task, alias, -1, host);
 }
 
-/** \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.
- *
- * 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.
- */
-MSG_error_t MSG_channel_select_from(m_channel_t channel,
-                                   double max_duration, int *PID)
+MSG_error_t
+MSG_task_receive(m_task_t * task, const char* alias)
 {
-  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->s_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_receive_with_timeout(task, alias, -1);
 }
 
-
-/** \ingroup msg_gos_functions
-
- * \brief Return the number of tasks waiting to be received on a \a
-   channel and sent by \a host.
- *
- * 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.
- */
-int MSG_task_probe_from_host(int channel, m_host_t host)
+MSG_error_t
+MSG_task_receive_with_timeout(m_task_t * task, const char* alias, double timeout)
 {
-  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 MSG_task_receive_ext(task, alias, timeout, NULL);
+}
 
-  return count;
+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 Put a task on a channel of an
- * host (with a timeout on the waiting of the destination host) and
- * waits for the end of the transmission.
+
+/** \ingroup msg_gos_functions
+ * \brief Put a task on a channel of an host and waits for the end of the
+ * transmission.
  *
  * This function is used for describing the behavior of an agent. It
- * takes four parameter.
+ * 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
@@ -422,132 +405,37 @@ 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 
  * \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_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_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(m_task_t task, m_host_t dest, m_channel_t channel)
 {
-
-
-  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;
-  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;
-
-       task_simdata->using++;
-  local_host = ((simdata_process_t) process->simdata)->m_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) {
-    xbt_ex_t e;
-               double time;
-               double time_elapsed;
-               time = SIMIX_get_clock();
-    TRY {
-               /*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,
-                                               max_duration-time_elapsed);
-                               if ((task->simdata->comm != NULL) &&
-                                               (SIMIX_action_get_state(task->simdata->comm) != SURF_ACTION_RUNNING))
-                                       break;
-                       }
-    } CATCH(e) {
-      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) {
-         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 {
-       RETHROW;
-      }
-    }
-  } else {
-               while (1) {
-                       SIMIX_cond_wait(task->simdata->cond, task->simdata->mutex);
-                       if (SIMIX_action_get_state(task->simdata->comm) != SURF_ACTION_RUNNING)
-                               break;
-               }
-  }
-
-  DEBUG1("Action terminated %s", task->name);
-  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->s_host) == 0) {
-    MSG_RETURN(MSG_HOST_FAILURE);
-  } else {
-    MSG_RETURN(MSG_TRANSFER_FAILURE);
-  }
+       return MSG_task_put_with_timeout(task, dest, channel, -1.0);
 }
 
 /** \ingroup msg_gos_functions
- * \brief Put a task on a channel of an host and waits for the end of the
- * transmission.
+ * \brief Does exactly the same as MSG_task_put but with a bounded transmition
+ * rate.
+ *
+ * \sa MSG_task_put
+ */
+MSG_error_t
+MSG_task_put_bounded(m_task_t task, m_host_t dest, m_channel_t channel, double maxrate)
+{
+       task->simdata->rate = maxrate;
+       return MSG_task_put(task, dest, channel);
+}
+
+/** \ingroup msg_gos_functions \brief Put a task on a channel of an
+ * host (with a timeout on the waiting of the destination host) and
+ * waits for the end of the transmission.
  *
  * This function is used for describing the behavior of an agent. It
- * takes three parameter.
+ * takes four 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
@@ -562,271 +450,323 @@ MSG_error_t MSG_task_put_with_timeout(m_task_t task, m_host_t dest,
  * \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 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)
  #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(m_task_t task, m_host_t dest, m_channel_t channel)
+MSG_error_t
+MSG_task_put_with_timeout(m_task_t task, m_host_t dest, m_channel_t channel, double timeout)
 {
-  return MSG_task_put_with_timeout(task, dest, channel, -1.0);
+       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);
 }
 
-/** \ingroup msg_gos_functions
- * \brief Does exactly the same as MSG_task_put but with a bounded transmition 
- * rate.
- *
- * \sa MSG_task_put
- */
-MSG_error_t MSG_task_put_bounded(m_task_t task,
-                                m_host_t dest, m_channel_t channel,
-                                double max_rate)
+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);
+}
+
+
+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)
 {
-  MSG_error_t res = MSG_OK;
-  task->simdata->rate = max_rate;
-  res = MSG_task_put(task, dest, channel);
-  return (res);
+       CHECK_HOST();
+
+       return !MSG_mailbox_is_empty(MSG_mailbox_get_by_alias(alias));
 }
 
 /** \ingroup msg_gos_functions
- * \brief Executes a task and waits for its termination.
+ * \brief Test whether there is a pending communication on a channel.
  *
- * 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 a pending communication and 0 otherwise
  */
-MSG_error_t MSG_task_execute(m_task_t task)
+int
+MSG_task_Iprobe(m_channel_t channel)
 {
-  simdata_task_t simdata = NULL;
-  m_process_t self = MSG_process_self();
+  xbt_assert1((channel >= 0) && (channel < msg_global->max_channel), "Invalid channel %d", channel);
+
   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->m_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_cond_wait(simdata->cond, simdata->mutex);
-  SIMIX_unregister_action_to_condition(simdata->compute, simdata->cond);
-  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);
-  }
+  return !MSG_mailbox_is_empty(MSG_mailbox_get_by_channel(MSG_host_self(), channel));
 }
 
+/** \ingroup msg_gos_functions
 
-/** \ingroup m_task_management
* \brief Creates a new #m_task_t (a parallel one....).
+ * \brief Return the number of tasks waiting to be received on a \a
  channel and sent by \a host.
  *
- * 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 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.
  */
-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
+MSG_task_probe_from_host(int channel, m_host_t host)
 {
-  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->using = 1;
-  simdata->sender = NULL;
-  simdata->receiver = NULL;
-  simdata->source = NULL;
-
-  simdata->host_nb = host_nb;
-  simdata->host_list = xbt_new0(void *, 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->s_host;
-
-  return task;
+       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);
 
-MSG_error_t MSG_parallel_task_execute(m_task_t task)
-{
-  simdata_task_t simdata = NULL;
-  m_process_t self = MSG_process_self();
-  CHECK_HOST();
+}
 
-  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->m_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_cond_wait(simdata->cond, simdata->mutex);
-  SIMIX_unregister_action_to_condition(simdata->compute, simdata->cond);
-  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);
-  }
+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 Sleep for the specified number of seconds
- *
- * Makes the current process sleep until \a time seconds have elapsed.
+ * \brief Test whether there is a pending communication on a channel, and who sent it.
  *
- * \param nb_sec a number of second
+ * 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_process_sleep(double nb_sec)
+int
+MSG_task_probe_from(m_channel_t channel)
 {
-  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->s_process),
-                        nb_sec);
-
-  mutex = SIMIX_mutex_init();
-  SIMIX_mutex_lock(mutex);
-  /* create conditional and register action to it */
-  cond = SIMIX_cond_init();
-
-  SIMIX_register_action_to_condition(act_sleep, cond);
-  SIMIX_cond_wait(cond, mutex);
-  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_CPU_OFF) {
-      SIMIX_action_destroy(act_sleep);
-      MSG_RETURN(MSG_HOST_FAILURE);
-    }
-  } else {
-    SIMIX_action_destroy(act_sleep);
-    MSG_RETURN(MSG_HOST_FAILURE);
-  }
-
-
-  MSG_RETURN(MSG_OK);
+       m_task_t task;
+
+       CHECK_HOST();
+
+       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);
 }
 
-/** \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)
+int
+MSG_task_listen_from(const char* alias)
 {
-  xbt_die("not implemented yet");
-  return 0;
+       m_task_t task;
+
+       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.
  *
- * \brief Return the last value returned by a MSG function (except
- * MSG_get_errno...).
+ * 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.
  */
-MSG_error_t MSG_get_errno(void)
+MSG_error_t
+MSG_channel_select_from(m_channel_t channel,double timeout, int *PID)
+{
+       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;
+
+       xbt_assert1((channel >= 0) && (channel < msg_global->max_channel), "Invalid channel %d",channel);
+
+       if(PID)
+       {
+               *PID = -1;
+       }
+
+       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;
+
+               mailbox = MSG_mailbox_get_by_channel(MSG_host_self(), channel);
+
+               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_alias_select_from(const char* alias, double timeout, int* PID)
 {
-  return PROCESS_GET_ERRNO();
+       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;
+
+       if (PID)
+       {
+               *PID = -1;
+       }
+
+       if(timeout == 0.0)
+       {
+               *PID = MSG_task_listen_from(alias);
+               MSG_RETURN(MSG_OK);
+       }
+       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);
+
+               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;
+               }
+
+               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);
+       }
 }
+
+
+
+
+