From 7bd18214a7d3c4e11ada1a3fe53ebfca9c7dc00f Mon Sep 17 00:00:00 2001
From: Thananon Patinyasakdikul <apatinya@cisco.com>
Date: Wed, 15 Jun 2016 07:35:04 -0700
Subject: [PATCH] Fix btl/usnic deadlock when the connectivity check is turned
 off.

---
 opal/mca/btl/usnic/btl_usnic_cclient.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/opal/mca/btl/usnic/btl_usnic_cclient.c b/opal/mca/btl/usnic/btl_usnic_cclient.c
index 6370c2c790..3f0279d463 100644
--- a/opal/mca/btl/usnic/btl_usnic_cclient.c
+++ b/opal/mca/btl/usnic/btl_usnic_cclient.c
@@ -228,13 +228,15 @@ int opal_btl_usnic_connectivity_ping(uint32_t src_ipv4_addr, int src_port,
                                      uint32_t dest_netmask, int dest_port,
                                      char *dest_nodename,
                                      size_t max_msg_size)
-{  
-    OPAL_THREAD_LOCK(&btl_usnic_lock);
+{
     /* If connectivity checking is not enabled, do nothing */
     if (!mca_btl_usnic_component.connectivity_enabled) {
         return OPAL_SUCCESS;
     }
 
+    /* Protect opal_fd_write for multithreaded case */
+    OPAL_THREAD_LOCK(&btl_usnic_lock);
+
     /* Send the PING command */
     int id = CONNECTIVITY_AGENT_CMD_PING;
     if (OPAL_SUCCESS != opal_fd_write(agent_fd, sizeof(id), &id)) {
@@ -260,6 +262,8 @@ int opal_btl_usnic_connectivity_ping(uint32_t src_ipv4_addr, int src_port,
         ABORT("usnic connectivity client IPC write failed");
         /* Will not return */
     }
+
+    /* Unlock and return */
     OPAL_THREAD_UNLOCK(&btl_usnic_lock);
 
     return OPAL_SUCCESS;