X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/7481472c078583c976f9eee9b31a687b9881ea54..5a3c64d7f437f3e64f52752b8ab2a40d04705bca:/src/gras/Msg/msg.c

diff --git a/src/gras/Msg/msg.c b/src/gras/Msg/msg.c
index 3354c00b67..ec047a4eee 100644
--- a/src/gras/Msg/msg.c
+++ b/src/gras/Msg/msg.c
@@ -8,18 +8,24 @@
  * under the terms of the license (GNU LGPL) which comes with this package. */
 
 #include "xbt/ex.h"
+#include "xbt/ex_interface.h"
 #include "gras/Msg/msg_private.h"
 #include "gras/Virtu/virtu_interface.h"
 #include "gras/DataDesc/datadesc_interface.h"
 #include "gras/Transport/transport_interface.h" /* gras_select */
+#include "portable.h" /* execinfo when available to propagate exceptions */
 
+#ifndef MIN
 #define MIN(a,b) ((a) < (b) ? (a) : (b))
+#endif
 
 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(gras_msg,gras,"High level messaging");
 
 xbt_set_t _gras_msgtype_set = NULL;
 static char *make_namev(const char *name, short int ver);
 char _GRAS_header[6];
+const char *e_gras_msg_kind_names[e_gras_msg_kind_count]=
+  {"UNKNOWN","ONEWAY","RPC call","RPC answer","RPC error"};
 
 /*
  * Creating procdata for this module
@@ -115,33 +121,14 @@ static char *make_namev(const char *name, short int ver) {
   return namev;
 }
 
-/** @brief declare a new message type of the given name. It only accepts the given datadesc as payload
- *
- * @param name: name as it should be used for logging messages (must be uniq)
- * @param payload: datadescription of the payload
- */
-void gras_msgtype_declare(const char           *name,
-			  gras_datadesc_type_t  payload) {
-   gras_msgtype_declare_v(name, 0, payload);
-}
+/* Internal function doing the crude work of registering messages */
+void 
+gras_msgtype_declare_ext(const char           *name,
+			 short int             version,
+			 e_gras_msg_kind_t     kind, 
+			 gras_datadesc_type_t  payload_request,
+			 gras_datadesc_type_t  payload_answer) {
 
-/** @brief declare a new versionned message type of the given name and payload
- *
- * @param name: name as it should be used for logging messages (must be uniq)
- * @param version: something like versionning symbol
- * @param payload: datadescription of the payload
- *
- * Registers a message to the GRAS mechanism. Use this version instead of 
- * gras_msgtype_declare when you change the semantic or syntax of a message and
- * want your programs to be able to deal with both versions. Internally, each
- * will be handled as an independent message type, so you can register 
- * differents for each of them.
- */
-void
-gras_msgtype_declare_v(const char           *name,
-		       short int             version,
-		       gras_datadesc_type_t  payload) {
- 
   gras_msgtype_t msgtype=NULL;
   char *namev=make_namev(name,version);
   volatile int found = 0;
@@ -157,48 +144,100 @@ gras_msgtype_declare_v(const char           *name,
   }
 
   if (found) {
-    VERB2("Re-register version %d of message '%s' (same payload, ignored).",
+    VERB2("Re-register version %d of message '%s' (same kind & payload, ignored).",
 	  version, name);
-    xbt_assert3(!gras_datadesc_type_cmp(msgtype->ctn_type, payload),
+    xbt_assert3(msgtype->kind == kind,
+		"Message %s re-registered as a %s (it was known as a %s)",
+		namev,e_gras_msg_kind_names[kind],e_gras_msg_kind_names[msgtype->kind]);
+    xbt_assert3(!gras_datadesc_type_cmp(msgtype->ctn_type, payload_request),
 		 "Message %s re-registred with another payload (%s was %s)",
-		 namev,gras_datadesc_get_name(payload),
+		 namev,gras_datadesc_get_name(payload_request),
 		 gras_datadesc_get_name(msgtype->ctn_type));
 
+    xbt_assert3(!gras_datadesc_type_cmp(msgtype->answer_type, payload_answer),
+	     "Message %s re-registred with another answer payload (%s was %s)",
+		 namev,gras_datadesc_get_name(payload_answer),
+		 gras_datadesc_get_name(msgtype->answer_type));
+
     return ; /* do really ignore it */
 
   }
 
-  VERB3("Register version %d of message '%s' (payload: %s).", 
-	version, name, gras_datadesc_get_name(payload));    
+  VERB4("Register version %d of message '%s' "
+	"(payload: %s; answer payload: %s).", 
+	version, name, gras_datadesc_get_name(payload_request),
+	gras_datadesc_get_name(payload_answer));    
 
   msgtype = xbt_new(s_gras_msgtype_t,1);
   msgtype->name = (namev == name ? strdup(name) : namev);
   msgtype->name_len = strlen(namev);
   msgtype->version = version;
-  msgtype->ctn_type = payload;
+  msgtype->kind = kind;
+  msgtype->ctn_type = payload_request;
+  msgtype->answer_type = payload_answer;
 
   xbt_set_add(_gras_msgtype_set, (xbt_set_elm_t)msgtype,
 	       &gras_msgtype_free);
 }
 
-/** @brief retrive an existing message type from its name. */
+
+/** @brief declare a new message type of the given name. It only accepts the given datadesc as payload
+ *
+ * @param name: name as it should be used for logging messages (must be uniq)
+ * @param payload: datadescription of the payload
+ */
+void gras_msgtype_declare(const char           *name,
+			  gras_datadesc_type_t  payload) {
+   gras_msgtype_declare_ext(name, 0, e_gras_msg_kind_oneway, payload, NULL);
+}
+
+
+
+/** @brief declare a new versionned message type of the given name and payload
+ *
+ * @param name: name as it should be used for logging messages (must be uniq)
+ * @param version: something like versionning symbol
+ * @param payload: datadescription of the payload
+ *
+ * Registers a message to the GRAS mechanism. Use this version instead of 
+ * gras_msgtype_declare when you change the semantic or syntax of a message and
+ * want your programs to be able to deal with both versions. Internally, each
+ * will be handled as an independent message type, so you can register 
+ * differents for each of them.
+ */
+void
+gras_msgtype_declare_v(const char           *name,
+		       short int             version,
+		       gras_datadesc_type_t  payload) {
+ 
+   gras_msgtype_declare_ext(name, version, 
+			    e_gras_msg_kind_oneway, payload, NULL);
+}
+
+/** @brief retrieve an existing message type from its name. */
 gras_msgtype_t gras_msgtype_by_name (const char *name) {
   return gras_msgtype_by_namev(name,0);
 }
 
-/** @brief retrive an existing message type from its name and version. */
+/** @brief retrieve an existing message type from its name and version. */
 gras_msgtype_t gras_msgtype_by_namev(const char      *name,
 				     short int        version) {
-  gras_msgtype_t res;
+  gras_msgtype_t res = NULL;
   char *namev = make_namev(name,version); 
+  xbt_ex_t e;
 
-  res = (gras_msgtype_t)xbt_set_get_by_name(_gras_msgtype_set, namev);
+  TRY {
+    res = (gras_msgtype_t)xbt_set_get_by_name(_gras_msgtype_set, namev);
+  } CATCH(e) {
+    xbt_ex_free(e);
+    THROW1(not_found_error,0,"No registred message of that name: %s",name);
+  }
   if (name != namev) 
     free(namev);
   
   return res;
 }
-/** @brief retrive an existing message type from its name and version. */
+/** @brief retrieve an existing message type from its name and version. */
 gras_msgtype_t gras_msgtype_by_id(int id) {
   return (gras_msgtype_t)xbt_set_get_by_id(_gras_msgtype_set, id);
 }
@@ -208,11 +247,9 @@ gras_msgtype_t gras_msgtype_by_id(int id) {
  * @param timeout: How long should we wait for this message.
  * @param msgt_want: type of awaited msg (or NULL if I'm enclined to accept any message)
  * @param expe_want: awaited expeditot (match on hostname, not port; NULL if not relevant)
- * @param payl_filter: function returning true or false when passed a payload. Messages for which it returns false are not selected. (NULL if not relevant)
+ * @param filter: function returning true or false when passed a payload. Messages for which it returns false are not selected. (NULL if not relevant)
  * @param filter_ctx: context passed as second argument of the filter (a pattern to match?)
- * @param[out] msgt_got: where to write the descriptor of the message we got
- * @param[out] expe_got: where to create a socket to answer the incomming message
- * @param[out] payl_got: where to write the payload of the incomming message
+ * @param[out] msg_got: where to write the message we got
  *
  * Every message of another type received before the one waited will be queued
  * and used by subsequent call to this function or gras_msg_handle().
@@ -220,22 +257,22 @@ gras_msgtype_t gras_msgtype_by_id(int id) {
 
 void
 gras_msg_wait_ext(double           timeout,    
+
 		  gras_msgtype_t   msgt_want,
 		  gras_socket_t    expe_want,
-		  int_f_pvoid_pvoid_t payl_filter,
-		  void               *filter_ctx, 
-		  gras_msgtype_t  *msgt_got,
-		  gras_socket_t   *expe_got,
-		  void            *payl_got) {
+		  gras_msg_filter_t filter,
+		  void             *filter_ctx, 
+
+		  gras_msg_t       msg_got) {
 
   s_gras_msg_t msg;
   double start, now;
   gras_msg_procdata_t pd=(gras_msg_procdata_t)gras_libdata_by_id(gras_msg_libdata_id);
   int cpt;
 
-  xbt_assert0(msgt_want,"Cannot wait for the NULL message");
+  xbt_assert0(msg_got,"msg_got is an output parameter");
 
-  VERB1("Waiting for message '%s'",msgt_want->name);
+  VERB1("Waiting for message '%s'",msgt_want?msgt_want->name:"(any)");
 
   start = now = gras_os_time();
 
@@ -243,15 +280,9 @@ gras_msg_wait_ext(double           timeout,
     if ( (   !msgt_want || (msg.type->code == msgt_want->code)) 
 	 && (!expe_want || (!strcmp( gras_socket_peer_name(msg.expe),
 				     gras_socket_peer_name(expe_want))))
-	 && (!payl_filter || payl_filter(msg.payl,filter_ctx))) {
-
-      if (expe_got)
-        *expe_got = msg.expe;
-      if (msgt_got)
-	*msgt_got = msg.type;
-      if (payl_got) 
-	memcpy(payl_got, msg.payl, msg.payl_size);
-      free(msg.payl);
+	 && (!filter || filter(&msg,filter_ctx))) {
+
+      memcpy(msg_got,&msg,sizeof(s_gras_msg_t));
       xbt_dynar_cursor_rm(pd->msg_queue, &cpt);
       VERB0("The waited message was queued");
       return;
@@ -261,31 +292,29 @@ gras_msg_wait_ext(double           timeout,
   while (1) {
     memset(&msg,sizeof(msg),0);
 
-    msg.expe = gras_trp_select(timeout - now + start);
+    msg.expe = gras_trp_select(timeout ? timeout - now + start : 0);
     gras_msg_recv(msg.expe, &msg);
+    DEBUG0("Got a message from the socket");
 
     if ( (   !msgt_want || (msg.type->code == msgt_want->code)) 
 	 && (!expe_want || (!strcmp( gras_socket_peer_name(msg.expe),
 				     gras_socket_peer_name(expe_want))))
-	 && (!payl_filter || payl_filter(msg.payl,filter_ctx))) {
-
-      if (expe_got)
-      	*expe_got=msg.expe;
-      if (msgt_got)
-	*msgt_got = msg.type;
-      if (payl_got) 
-	memcpy(payl_got, msg.payl, msg.payl_size);
-      free(msg.payl);
+	 && (!filter || filter(&msg,filter_ctx))) {
+
+      memcpy(msg_got,&msg,sizeof(s_gras_msg_t));
+      DEBUG0("Message matches expectations. Use it.");
       return;
     }
+    DEBUG0("Message does not match expectations. Queue it.");
 
     /* not expected msg type. Queue it for later */
     xbt_dynar_push(pd->msg_queue,&msg);
     
     now=gras_os_time();
-    if (now - start + 0.001 < timeout) {
+    if (now - start + 0.001 > timeout) {
       THROW1(timeout_error,  now-start+0.001-timeout,
-	     "Timeout while waiting for msg %s",msgt_want->name);
+	     "Timeout while waiting for msg '%s'",
+	     msgt_want?msgt_want->name:"(any)");
     }
   }
 
@@ -307,10 +336,84 @@ gras_msg_wait(double           timeout,
 	      gras_msgtype_t   msgt_want,
 	      gras_socket_t   *expeditor,
 	      void            *payload) {
+  s_gras_msg_t msg;
+
+  gras_msg_wait_ext(timeout,
+		    msgt_want, NULL,      NULL, NULL,
+		    &msg);
+
+  if (msgt_want->ctn_type) {
+    xbt_assert1(payload,
+		"Message type '%s' convey a payload you must accept",
+		msgt_want->name);
+  } else {
+    xbt_assert1(!payload,
+		"No payload was declared for message type '%s'",
+		msgt_want->name);
+  }
+
+  if (payload) {
+    memcpy(payload,msg.payl,msg.payl_size);
+    free(msg.payl);
+  }
 
-  return gras_msg_wait_ext(timeout,
-			   msgt_want, NULL,      NULL, NULL,
-			   NULL,      expeditor, payload);
+  if (expeditor)
+    *expeditor = msg.expe;
+}
+
+static int gras_msg_wait_or_filter(gras_msg_t msg, void *ctx) {
+  xbt_dynar_t dyn=(xbt_dynar_t)ctx;
+  int res =  xbt_dynar_member(dyn,msg->type);
+  if (res)
+    VERB1("Got matching message (type=%s)",msg->type->name);
+  else
+    VERB0("Got message not matching our expectations");
+  return res;
+}
+/** \brief Waits for a message to come in over a given socket. 
+ *
+ * @param timeout: How long should we wait for this message.
+ * @param msgt_want: a dynar containing all accepted message type
+ * @param[out] ctx: the context of received message (in case it's a RPC call we want to answer to)
+ * @param[out] msgt_got: indice in the dynar of the type of the received message 
+ * @param[out] payload: where to write the payload of the incomming message
+ * @return the error code (or no_error).
+ *
+ * Every message of a type not in the accepted list received before the one
+ * waited will be queued and used by subsequent call to this function or
+ * gras_msg_handle().
+ *
+ * If you are interested in the context, pass the address of a s_gras_msg_cb_ctx_t variable.
+ */
+void gras_msg_wait_or(double         timeout,
+                      xbt_dynar_t    msgt_want,
+		      gras_msg_cb_ctx_t *ctx,
+                      int           *msgt_got,
+                      void          *payload) {
+  s_gras_msg_t msg;
+
+  VERB1("Wait %f seconds for several message types",timeout);
+  gras_msg_wait_ext(timeout,
+		    NULL, NULL,      
+		    &gras_msg_wait_or_filter, (void*)msgt_want,
+		    &msg);
+
+  if (msg.type->ctn_type) {
+    xbt_assert1(payload,
+		"Message type '%s' convey a payload you must accept",
+		msg.type->name);
+  } /* don't check the other side since some of the types may have a payload */
+
+  if (payload && msg.type->ctn_type) {
+    memcpy(payload,msg.payl,msg.payl_size);
+    free(msg.payl);
+  }
+
+  if (ctx) 
+    *ctx=gras_msg_cb_ctx_new(msg.expe,msg.type,msg.ID,60);
+
+  if (msgt_got)
+    *msgt_got = xbt_dynar_search(msgt_want,msg.type);
 }
 
 
@@ -321,31 +424,70 @@ gras_msg_send(gras_socket_t   sock,
 	      gras_msgtype_t  msgtype,
 	      void           *payload) {
 
-  gras_msg_send_ext(sock, e_gras_msg_kind_oneway, msgtype, payload);
+  if (msgtype->ctn_type) {
+    xbt_assert1(payload,
+		"Message type '%s' convey a payload you must provide",
+		msgtype->name);
+  } else {
+    xbt_assert1(!payload,
+		"No payload was declared for message type '%s'",
+		msgtype->name);
+  }
+
+  DEBUG2("Send a oneway message of type '%s'. Payload=%p",
+	 msgtype->name,payload);
+  gras_msg_send_ext(sock, e_gras_msg_kind_oneway,0, msgtype, payload);
+  VERB2("Sent a oneway message of type '%s'. Payload=%p",
+	msgtype->name,payload);
 }
 
+/** @brief Handle all messages arriving within the given period
+ *
+ * @param timeOut: How long to wait for incoming messages (in seconds)
+ * @return the error code (or no_error).
+ *
+ * Messages are dealed with just like gras_msg_handle() would do. The
+ * difference is that gras_msg_handle() handles at most one message (or wait up
+ * to timeout second when no message arrives) while this function handles any
+ * amount of messages, and lasts the given period in any case.
+ */
+void 
+gras_msg_handleall(double period) {
+  xbt_ex_t e;
+  double begin=gras_os_time();
+  double now;
+
+  do {
+    now=gras_os_time();
+    TRY{
+      gras_msg_handle(period - now + begin);
+    } CATCH(e) {
+      if (e.category != timeout_error) 
+	RETHROW0("Error while waiting for messages: %s");
+      xbt_ex_free(e);
+    }
+  } while (now - begin < period);
+}
 /** @brief Handle an incomming message or timer (or wait up to \a timeOut seconds)
  *
  * @param timeOut: How long to wait for incoming messages (in seconds)
  * @return the error code (or no_error).
  *
- * Messages are passed to the callbacks.
+ * Messages are passed to the callbacks. See also gras_msg_handleall().
  */
 void
 gras_msg_handle(double timeOut) {
   
   double          untiltimer;
    
-  int             cpt;
+  int             cpt, ran_ok;
 
   s_gras_msg_t    msg;
-  gras_socket_t   expeditor=NULL;
-  void           *payload=NULL;
-  gras_msgtype_t  msgtype=NULL;
 
   gras_msg_procdata_t pd=(gras_msg_procdata_t)gras_libdata_by_id(gras_msg_libdata_id);
   gras_cblist_t  *list=NULL;
   gras_msg_cb_t       cb;
+  s_gras_msg_cb_ctx_t ctx;
    
   int timerexpected, timeouted;
   xbt_ex_t e;
@@ -353,7 +495,7 @@ gras_msg_handle(double timeOut) {
   VERB1("Handling message within the next %.2fs",timeOut);
   
   untiltimer = gras_msg_timer_handle();
-  DEBUG2("[%.0f] Next timer in %f sec", gras_os_time(), untiltimer);
+  DEBUG1("Next timer in %f sec", untiltimer);
   if (untiltimer == 0.0) {
      /* A timer was already elapsed and handled */
      return;
@@ -370,12 +512,9 @@ gras_msg_handle(double timeOut) {
   if (xbt_dynar_length(pd->msg_queue)) {
     DEBUG0("Get a message from the queue");
     xbt_dynar_shift(pd->msg_queue,&msg);
-    expeditor = msg.expe;
-    msgtype   = msg.type;
-    payload   = msg.payl;
   } else {
     TRY {
-      expeditor = gras_trp_select(timeOut);
+      msg.expe = gras_trp_select(timeOut);
     } CATCH(e) {
       if (e.category != timeout_error)
 	RETHROW;
@@ -386,12 +525,15 @@ gras_msg_handle(double timeOut) {
     if (!timeouted) {
       TRY {
 	/* FIXME: if not the right kind, queue it and recall ourself or goto >:-) */
-	gras_msg_recv(expeditor, &msg);
-	msgtype   = msg.type;
-	payload   = msg.payl;
+	gras_msg_recv(msg.expe, &msg);
+	DEBUG1("Received a msg from the socket kind:%s",
+	       e_gras_msg_kind_names[msg.kind]);
+    
       } CATCH(e) {
-	RETHROW1("Error caught while receiving a message on select()ed socket %p: %s",
-	  	 expeditor);
+	RETHROW4("Error while receiving a message on select()ed socket %p to [%s]%s:%d: %s",
+		 msg.expe,
+		 gras_socket_peer_proc(msg.expe),gras_socket_peer_name(msg.expe),
+		 gras_socket_peer_port(msg.expe));
       }
     }
   }
@@ -415,39 +557,92 @@ gras_msg_handle(double timeOut) {
 	
      } else {
 	/* select timeouted, and no timer elapsed. Nothing to do */
-       THROW0(timeout_error, 0, "No new message or timer");
+       THROW1(timeout_error, 0, "No new message or timer (delay was %f)",
+	      timeOut);
      }
      
   }
    
   /* A message was already there or arrived in the meanwhile. handle it */
   xbt_dynar_foreach(pd->cbl_list,cpt,list) {
-    if (list->id == msgtype->code) {
+    if (list->id == msg.type->code) {
       break;
     } else {
       list=NULL;
     }
   }
   if (!list) {
-    INFO1("No callback for the incomming '%s' message. Discarded.", 
-	  msgtype->name);
+    INFO3("No callback for the incomming '%s' message (from %s:%d). Discarded.", 
+	  msg.type->name,
+	  gras_socket_peer_name(msg.expe),gras_socket_peer_port(msg.expe));
     WARN0("FIXME: gras_datadesc_free not implemented => leaking the payload");
     return;
   }
   
-  xbt_dynar_foreach(list->cbs,cpt,cb) { 
-    VERB3("Use the callback #%d (@%p) for incomming msg %s",
-          cpt+1,cb,msgtype->name);
-    if ((*cb)(expeditor,payload)) {
-      /* cb handled the message */
-      free(payload);
-      return;
+  ctx.expeditor = msg.expe;
+  ctx.ID = msg.ID;
+  ctx.msgtype = msg.type;
+
+  switch (msg.kind) {
+  case e_gras_msg_kind_oneway:
+  case e_gras_msg_kind_rpccall:
+    ran_ok=0;
+    TRY {
+      xbt_dynar_foreach(list->cbs,cpt,cb) { 
+	if (!ran_ok) {
+	  DEBUG4("Use the callback #%d (@%p) for incomming msg %s (payload_size=%d)",
+		cpt+1,cb,msg.type->name,msg.payl_size);
+	  if ((*cb)(&ctx,msg.payl)) {
+	    /* cb handled the message */
+	    free(msg.payl);
+	    ran_ok = 1;
+	  }
+	}
+      }
+    } CATCH(e) {
+      free(msg.payl);
+      if (msg.type->kind == e_gras_msg_kind_rpccall) {
+	/* The callback raised an exception, propagate it on the network */
+	if (!e.remote) { /* the exception is born on this machine */
+	  e.host = (char*)gras_os_myname();
+	  xbt_ex_setup_backtrace(&e);
+	} 
+	VERB5("Propagate %s exception ('%s') from '%s' RPC cb back to %s:%d",
+	      (e.remote ? "remote" : "local"),
+	      e.msg,
+	      msg.type->name,
+	      gras_socket_peer_name(msg.expe),
+	      gras_socket_peer_port(msg.expe));
+	gras_msg_send_ext(msg.expe, e_gras_msg_kind_rpcerror,
+			  msg.ID, msg.type, &e);
+	xbt_ex_free(e);
+	ran_ok=1;
+      } else {
+	RETHROW0("Callback raised an exception: %s");
+      }
     }
+    if (!ran_ok)
+      THROW1(mismatch_error,0,
+	     "Message '%s' refused by all registered callbacks", msg.type->name);
+    /* FIXME: gras_datadesc_free not implemented => leaking the payload */
+    break;
+
+
+  case e_gras_msg_kind_rpcanswer:
+    INFO1("Unexpected RPC answer discarded (type: %s)", msg.type->name);
+    WARN0("FIXME: gras_datadesc_free not implemented => leaking the payload");
+    return;
+
+  case e_gras_msg_kind_rpcerror:
+    INFO1("Unexpected RPC error discarded (type: %s)", msg.type->name);
+    WARN0("FIXME: gras_datadesc_free not implemented => leaking the payload");
+    return;
+
+  default:
+    THROW1(unknown_error,0,
+    	   "Cannot handle messages of kind %d yet",msg.type->kind);
   }
 
-  /* FIXME: gras_datadesc_free not implemented => leaking the payload */
-  THROW1(mismatch_error,0,
-	 "Message '%s' refused by all registered callbacks", msgtype->name);
 }
 
 void
@@ -527,3 +722,27 @@ gras_cb_unregister(gras_msgtype_t msgtype,
     VERB1("Ignoring removal of unexisting callback to msg id %d",
 	  msgtype->code);
 }
+
+/** \brief Retrieve the expeditor of the message */
+gras_socket_t gras_msg_cb_ctx_from(gras_msg_cb_ctx_t ctx) {
+  return ctx->expeditor;
+}
+/* \brief Creates a new message exchange context (user should never have to) */
+gras_msg_cb_ctx_t gras_msg_cb_ctx_new(gras_socket_t expe, 
+				      gras_msgtype_t msgtype,
+				      unsigned long int ID,
+				      double timeout) {
+  gras_msg_cb_ctx_t res=xbt_new(s_gras_msg_cb_ctx_t,1);
+  res->expeditor = expe;
+  res->msgtype = msgtype;
+  res->ID = ID;
+  res->timeout = timeout;
+  return res;
+}
+/* \brief Frees a message exchange context 
+ *
+ * This function is mainly useful with \ref gras_msg_wait_or, ie seldom.
+ */
+void gras_msg_cb_ctx_free(gras_msg_cb_ctx_t ctx) {
+  free(ctx);
+}