commit df4822ea169adc5c7c987fa077438f0ded1ac39b
Author: Emeric Brun <ebrun@haproxy.com>
Date:   Thu Oct 11 15:27:07 2018 +0200

    BUG/MEDIUM: mworker: segfault receiving SIGUSR1 followed by SIGTERM.
    
    This bug appeared only if nbthread > 1. Handling the pipe with the
    master, multiple threads of the same worker could process the deinit().
    
    In addition, deinit() was called while some other threads were still
    performing some tasks.
    
    This patch assign the handler of the pipe with master to only the first
    thread and removes the call to deinit() before exiting with an error.
    
    This patch should be backported in v1.8.
    
    (cherry picked from commit c8c0ed91cb4436491efd2ce2c4b4b1694aeeccca)
    [wt: adjusted context]
    Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/src/haproxy.c b/src/haproxy.c
index e0186ff9..1959dd0f 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -2349,7 +2349,13 @@ void mworker_pipe_handler(int fd)
 		break;
 	}
 
-	deinit();
+	/* At this step the master is down before
+	 * this worker perform a 'normal' exit.
+	 * So we want to exit with an error but
+	 * other threads could currently process
+	 * some stuff so we can't perform a clean
+	 * deinit().
+	 */
 	exit(EXIT_FAILURE);
 	return;
 }
@@ -2364,7 +2370,10 @@ void mworker_pipe_register()
 	fcntl(mworker_pipe[0], F_SETFL, O_NONBLOCK);
 	fdtab[mworker_pipe[0]].owner = mworker_pipe;
 	fdtab[mworker_pipe[0]].iocb = mworker_pipe_handler;
-	fd_insert(mworker_pipe[0], MAX_THREADS_MASK);
+	/* In multi-tread, we need only one thread to process
+	 * events on the pipe with master
+	 */
+	fd_insert(mworker_pipe[0], 1);
 	fd_want_recv(mworker_pipe[0]);
 }