Avoid lock when child dies

Interaction between pthread_cond_wait, pthread_broadcast
and signal may lead to lock when the child of afb-daemon dies.

To avoid that sad behavior, this commit defers the call to
"job_exit" using lazy job queueing.

Bug-AGL: SPEC-2720

Change-Id: Ifd1a56f4a439e1704f79a1291fa01f39b1640f29
Signed-off-by: Jose Bollo <jose.bollo@iot.bzh>

2 files changed, 18 insertions, 8 deletions

diff --git a/src/afb-session.c b/src/afb-session.c
index 1bdb59db..61aa3f61 100644
--- a/src/afb-session.c
+++ b/src/afb-session.c
@@ -579,7 +579,7 @@ static int cookeyidx(const void *key)
  * @param makecb	the creation function or NULL
  * @param freecb	the release function or NULL
  * @param closure	an argument for makecb or the value if makecb==NULL
- * @param replace	a boolean enforcing replecement of the previous value
+ * @param replace	a boolean enforcing replacement of the previous value
  *
  * @return the value of the cookie
  *
diff --git a/src/main-afb-daemon.c b/src/main-afb-daemon.c
index 7b92905f..3421be81 100644
--- a/src/main-afb-daemon.c
+++ b/src/main-afb-daemon.c
@@ -403,15 +403,25 @@ static struct afb_hsrv *start_http_server()
  | execute_command
  +--------------------------------------------------------- */
 
-static void wait_child_and_exit()
+static void exit_at_end()
 {
+	exit(0);
+}
+
+static void wait_child(int signum, void* arg)
+{
+	pid_t pid = (pid_t)(intptr_t)arg;
 	pid_t pidchld = childpid;
 
-	childpid = 0;
-	if (!SELF_PGROUP)
-		killpg(pidchld, SIGKILL);
-	waitpid(pidchld, NULL, 0);
-	exit(0);
+	if (pidchld == pid) {
+		childpid = 0;
+		if (!SELF_PGROUP)
+			killpg(pidchld, SIGKILL);
+		waitpid(pidchld, NULL, 0);
+		jobs_exit(exit_at_end);
+	} else {
+		waitpid(pid, NULL, 0);
+	}
 }
 
 static void on_sigchld(int signum, siginfo_t *info, void *uctx)
@@ -421,7 +431,7 @@ static void on_sigchld(int signum, siginfo_t *info, void *uctx)
 		case CLD_EXITED:
 		case CLD_KILLED:
 		case CLD_DUMPED:
-			jobs_exit(wait_child_and_exit);
+			jobs_queue_lazy(0, 0, wait_child, (void*)(intptr_t)info->si_pid);
 		default:
 			break;
 		}