From: Augustin Degomme <augustin.degomme@imag.fr>
Date: Thu, 11 Sep 2014 08:58:19 +0000 (+0200)
Subject: Fix bug in SMPI with permanent receive mode.
X-Git-Tag: v3_12~829
X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/commitdiff_plain/79bcf7d543aa95b4425f4a6791241978cd5233c7?ds=sidebyside

Fix bug in SMPI with permanent receive mode.
Receive can be posted with a size exceding the asynchronous threshold, while corresponding send was posted with a smaller size.
This is legal in MPI, but caused SMPI to put one request in the large mailbox and the other one in the small mailbox, thus preventing matching of messages, and causing deadlocks
Probing is used now, in order to try to match a message in the other mailbox before the actual operation.
---

diff --git a/src/smpi/smpi_base.c b/src/smpi/smpi_base.c
index 52eba549df..0166d5e0c0 100644
--- a/src/smpi/smpi_base.c
+++ b/src/smpi/smpi_base.c
@@ -336,7 +336,7 @@ MPI_Request smpi_mpi_recv_init(void *buf, int count, MPI_Datatype datatype,
 void smpi_mpi_start(MPI_Request request)
 {
   smx_rdv_t mailbox;
-
+  
   xbt_assert(!request->action, "Cannot (re)start a non-finished communication");
   request->flags &= ~PREPARED;
   request->flags &= ~FINISHED;
@@ -345,10 +345,22 @@ void smpi_mpi_start(MPI_Request request)
   if (request->flags & RECV) {
     print_request("New recv", request);
     //FIXME: if receive is posted with a large size, but send is smaller, mailboxes may not match !
+    
     if (request->flags & RMA || request->size < sg_cfg_get_int("smpi/async_small_thres"))
       mailbox = smpi_process_mailbox_small();
-    else
-      mailbox = smpi_process_mailbox();
+    else{
+      mailbox = smpi_process_mailbox_small();
+      XBT_VERB("Is there a corresponding send already posted the small mailbox?");
+    smx_action_t action = simcall_comm_iprobe(mailbox, 0, request->src,request->tag, &match_recv, (void*)request);
+    
+      if(action ==NULL){
+        XBT_VERB("No, nothing in the permanent receive mailbox");
+        mailbox = smpi_process_mailbox();
+      }else{
+        XBT_VERB("yes there was something for us in the other mailbox");
+      }
+    }
+
     // we make a copy here, as the size is modified by simix, and we may reuse the request in another receive later
     request->real_size=request->size;
     smpi_datatype_use(request->old_type);
@@ -368,7 +380,7 @@ void smpi_mpi_start(MPI_Request request)
   } else {
 
 
-    int receiver = request->dst;//smpi_group_index(smpi_comm_group(request->comm), request->dst);
+    int receiver = request->dst;
 
     #ifdef HAVE_TRACING
       int rank = request->src;
@@ -376,13 +388,17 @@ void smpi_mpi_start(MPI_Request request)
         TRACE_smpi_send(rank, rank, receiver,request->size);
       }
     #endif
-/*    if(receiver == MPI_UNDEFINED) {*/
-/*      XBT_WARN("Trying to send a message to a wrong rank");*/
-/*      return;*/
-/*    }*/
     print_request("New send", request);
     if (request->flags & RMA || request->size < sg_cfg_get_int("smpi/async_small_thres")) { // eager mode
-      mailbox = smpi_process_remote_mailbox_small(receiver);
+      mailbox = smpi_process_remote_mailbox(receiver);
+      XBT_VERB("Is there a corresponding recv already posted in the large mailbox?");
+      smx_action_t action = simcall_comm_iprobe(mailbox, 1,request->dst, request->tag, &match_send, (void*)request);
+      if(action ==NULL){
+        XBT_VERB("No, nothing in the large mailbox, message is to be sent on the small one");
+        mailbox = smpi_process_remote_mailbox_small(receiver);
+      }else{
+        XBT_VERB("yes there was something for us in the other mailbox");
+      }
     }else{
       XBT_DEBUG("Send request %p is not in the permanent receive mailbox (buf: %p)",request,request->buf);
       mailbox = smpi_process_remote_mailbox(receiver);
@@ -414,7 +430,15 @@ void smpi_mpi_start(MPI_Request request)
     request->real_size=request->size;
     smpi_datatype_use(request->old_type);
     smpi_comm_use(request->comm);
-
+    request->action =
+      simcall_comm_isend(SIMIX_process_from_PID(request->src+1), mailbox, request->size, -1.0,
+                         buf, request->real_size,
+                         &match_send,
+                         &xbt_free_f, // how to free the userdata if a detached send fails
+                         &smpi_comm_copy_buffer_callback,
+                         request,
+                         // detach if msg size < eager/rdv switch limit
+                         request->detached);
     //if we are giving back the control to the user without waiting for completion, we have to inject timings
     double sleeptime = 0.0;
     if(request->detached || (request->flags & (ISEND|SSEND))){// issend should be treated as isend
@@ -426,15 +450,7 @@ void smpi_mpi_start(MPI_Request request)
         simcall_process_sleep(sleeptime);
         XBT_DEBUG("sending size of %zu : sleep %f ", request->size, smpi_os(request->size));
     }
-    request->action =
-      simcall_comm_isend(SIMIX_process_from_PID(request->src+1), mailbox, request->size, -1.0,
-                         buf, request->real_size,
-                         &match_send,
-                         &xbt_free_f, // how to free the userdata if a detached send fails
-                         &smpi_comm_copy_buffer_callback,
-                         request,
-                         // detach if msg size < eager/rdv switch limit
-                         request->detached);
+
 
 #ifdef HAVE_TRACING
     /* FIXME: detached sends are not traceable (request->action == NULL) */