From 49e725625ae9a08f7b2953aeb7e6714f8cc9b4b2 Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Fri, 14 Sep 2018 07:51:31 -0600
Subject: [PATCH] libs/libc/wqueue/work_usrthread.c:  Eliminate a race
 condition noted by Xiang Xiao.

---
 libs/libc/wqueue/work_usrthread.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/libs/libc/wqueue/work_usrthread.c b/libs/libc/wqueue/work_usrthread.c
index 8918ccc9ac6..e28a4a20cad 100644
--- a/libs/libc/wqueue/work_usrthread.c
+++ b/libs/libc/wqueue/work_usrthread.c
@@ -255,6 +255,14 @@ void work_process(FAR struct usr_wqueue_s *wqueue)
         }
     }
 
+  /* Unlock the work queue before waiting.  In order to assure that these
+   * operations are atomic with respect to other user tasks, we disable
+   * pre-emption here.  Pre-emption will be re-enabled while we sleep.
+   */
+
+  sched_lock();
+  work_unlock();
+
   if (next == WORK_DELAY_MAX)
     {
       sigset_t set;
@@ -276,7 +284,7 @@ void work_process(FAR struct usr_wqueue_s *wqueue)
       usleep(next * USEC_PER_TICK);
     }
 
-  work_unlock();
+  sched_unlock();
 }
 
 /****************************************************************************