From 0ae2277796c3ec3f6434b5080c28a006460e46bc Mon Sep 17 00:00:00 2001
From: Brian Barrett <brbarret@open-mpi.org>
Date: Tue, 1 May 2012 15:53:00 +0000
Subject: [PATCH] Add a backoff mechanism for re-establishing communication

This commit was SVN r26366.
---
 ompi/mca/mtl/portals4/mtl_portals4_flowctl.c | 16 ++++++++++++++--
 ompi/mca/mtl/portals4/mtl_portals4_flowctl.h |  5 ++++-
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/ompi/mca/mtl/portals4/mtl_portals4_flowctl.c b/ompi/mca/mtl/portals4/mtl_portals4_flowctl.c
index 47a8fa002d..545cc98765 100644
--- a/ompi/mca/mtl/portals4/mtl_portals4_flowctl.c
+++ b/ompi/mca/mtl/portals4/mtl_portals4_flowctl.c
@@ -44,8 +44,6 @@ ompi_mtl_portals4_flowctl_init(void)
                         OBJ_CLASS(ompi_mtl_portals4_pending_request_t),
                         1, -1, 1);
 
-    OBJ_CONSTRUCT(&ompi_mtl_portals4.flowctl.mutex, opal_mutex_t);
-
     ompi_mtl_portals4.flowctl.slots = (ompi_mtl_portals4.queue_size - 3) / 3;
 
     ompi_mtl_portals4.flowctl.alert_req.type = portals4_req_flowctl;
@@ -200,6 +198,9 @@ ompi_mtl_portals4_flowctl_init(void)
 
     ompi_mtl_portals4.flowctl.num_children = 0;
 
+    gettimeofday(&ompi_mtl_portals4.flowctl.tv, NULL);
+    ompi_mtl_portals4.flowctl.backoff_count = 0;
+
     ret = OMPI_SUCCESS;
 
  error:
@@ -544,6 +545,7 @@ flowctl_fanout_callback(ptl_event_t *ev,
                         ompi_mtl_portals4_base_request_t *ptl_base_request)
 {
     int ret;
+    struct timeval tv;
 
     ompi_mtl_portals4.flowctl.flowctl_active = false;
     ret = PtlPTEnable(ompi_mtl_portals4.ni_h, ompi_mtl_portals4.recv_idx);
@@ -554,6 +556,16 @@ flowctl_fanout_callback(ptl_event_t *ev,
         return ret;
     }
 
+    gettimeofday(&tv, NULL);
+    if (((tv.tv_sec * 1000000 + tv.tv_usec) - 
+         (ompi_mtl_portals4.flowctl.tv.tv_sec * 1000000 + ompi_mtl_portals4.flowctl.tv.tv_usec)) 
+        < 1000000 * ompi_mtl_portals4.flowctl.backoff_count) {
+        usleep(++ompi_mtl_portals4.flowctl.backoff_count);
+    } else {
+        ompi_mtl_portals4.flowctl.backoff_count = 0;
+    }
+    ompi_mtl_portals4.flowctl.tv = tv;
+         
     ompi_mtl_portals4_pending_list_progress();
 
     OPAL_OUTPUT_VERBOSE((50, ompi_mtl_base_output,
diff --git a/ompi/mca/mtl/portals4/mtl_portals4_flowctl.h b/ompi/mca/mtl/portals4/mtl_portals4_flowctl.h
index 2b38647b1a..87e2d23e52 100644
--- a/ompi/mca/mtl/portals4/mtl_portals4_flowctl.h
+++ b/ompi/mca/mtl/portals4/mtl_portals4_flowctl.h
@@ -38,7 +38,6 @@ struct ompi_mtl_portals4_flowctl_t {
     opal_list_t active_sends;
     opal_list_t pending_sends;
     opal_free_list_t pending_fl;
-    opal_mutex_t mutex;
     int32_t slots;
 
     ompi_mtl_portals4_base_request_t alert_req;
@@ -70,6 +69,10 @@ struct ompi_mtl_portals4_flowctl_t {
     /** Flow control restart fan-out ME. */
     ptl_handle_me_t fanout_me_h;
 
+    /** last restart time */
+    struct timeval tv;
+    int backoff_count;
+
     size_t num_procs;
     size_t num_children;
     ptl_process_t children[2];