[mpich-commits] [mpich] MPICH primary repository branch, master, updated. v3.2b3-272-g7ca8ec3

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http://git.mpich.org/mpich.git/commitdiff/7ca8ec3fc9421261dcab47af36a9f5e4ef6c2e28

commit 7ca8ec3fc9421261dcab47af36a9f5e4ef6c2e28
Author: Xin Zhao <xinzhao3 at illinois.edu>
Date:   Tue Jul 21 21:15:32 2015 -0500

    Modify comments about request completion callback.
    
    Signed-off-by: Pavan Balaji <balaji at anl.gov>

diff --git a/src/include/mpiimpl.h b/src/include/mpiimpl.h
index cab4045..d90f8de 100644
--- a/src/include/mpiimpl.h
+++ b/src/include/mpiimpl.h
@@ -1547,9 +1547,28 @@ typedef struct MPID_Request {
     /* Errflag for NBC requests. Not used by other requests. */
     mpir_errflag_t errflag;
 
-    /* request_completed_cb: the callback function triggered when this request
-     * is completed, i.e. CC is set to 0. Inside request_completed_cb, progress
-     * engine should not be called. */
+    /* Notes about request_completed_cb:
+     *
+     *   1. The callback function is triggered when this requests
+     *      completion count reaches 0.
+     *
+     *   2. The callback function should be nonblocking.
+     *
+     *   3. The callback function should not poke the progress engine,
+     *      or call any function that pokes the progress engine.
+     *
+     *   4. The callback function can complete other requests, thus
+     *      calling those requests' callback functions.  However, the
+     *      recursion depth of request completion function is limited.
+     *      If we ever need deeper recurisve calls, we need to change
+     *      to an iterative design instead of a recursive design for
+     *      request completion.
+     *
+     *   5. In multithreaded programs, since the callback function is
+     *      nonblocking and never calls the progress engine, it would
+     *      never yield the lock to other threads.  So the recursion
+     *      should be multithreading-safe.
+     */
     int (*request_completed_cb)(struct MPID_Request *);
 
     /* Other, device-specific information */

http://git.mpich.org/mpich.git/commitdiff/aceee6d924abce30a14da0f1bb53ddedd841c99c

commit aceee6d924abce30a14da0f1bb53ddedd841c99c
Author: Xin Zhao <xinzhao3 at illinois.edu>
Date:   Tue Jul 21 21:14:41 2015 -0500

    Add an assert to check the recursion depth of MPID_Request_complete.
    
    We allow a depth of up to 2 for recursive calls of
    MPID_Request_complete.  Arbitrary levels of recursion can cause weird
    failures that might be hard to debug.  For now, a level of two is
    sufficient.  Currently this only happens when completing the user
    request in request-based RMA operations.
    
    Signed-off-by: Pavan Balaji <balaji at anl.gov>

diff --git a/src/mpid/ch3/src/ch3u_request.c b/src/mpid/ch3/src/ch3u_request.c
index 63e444c..53230f1 100644
--- a/src/mpid/ch3/src/ch3u_request.c
+++ b/src/mpid/ch3/src/ch3u_request.c
@@ -21,6 +21,9 @@
 #define MPID_REQUEST_PREALLOC 8
 #endif
 
+/* Max depth of recursive calls of MPID_Request_complete */
+#define REQUEST_CB_DEPTH 2
+
 MPID_Request MPID_Request_direct[MPID_REQUEST_PREALLOC] = {{0}};
 MPIU_Object_alloc_t MPID_Request_mem = {
     0, 0, 0, 0, MPID_REQUEST, sizeof(MPID_Request), MPID_Request_direct,
@@ -611,6 +614,10 @@ int MPID_Request_complete(MPID_Request *req)
 {
     int incomplete;
     int mpi_errno = MPI_SUCCESS;
+    static int called_cnt = 0;
+
+    MPIU_Assert(called_cnt <= REQUEST_CB_DEPTH);
+    called_cnt++;
 
     MPIDI_CH3U_Request_decrement_cc(req, &incomplete);
     if (!incomplete) {
@@ -627,6 +634,7 @@ int MPID_Request_complete(MPID_Request *req)
     }
 
  fn_exit:
+    called_cnt--;
     return mpi_errno;
  fn_fail:
     goto fn_exit;

-----------------------------------------------------------------------

Summary of changes:
 src/include/mpiimpl.h           |   25 ++++++++++++++++++++++---
 src/mpid/ch3/src/ch3u_request.c |    8 ++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)


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