From: David Goulet <dgoulet@efficios.com>
Date: Thu, 21 Nov 2013 18:02:40 +0000 (-0500)
Subject: Fix: use non block waitpid to lookup child state
X-Git-Tag: v2.4.0-rc2~37
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=077df0b372f77833c1de2dd9f534dec9e75696de;hp=dd2c2a1b8ad6c0fb516f7e7c1bf1adfa6b93b8e6

Fix: use non block waitpid to lookup child state

When daemonizing the session daemon, if the child fails *before* it
could set the recv_child_signal variable that indicates the parent to
exit, the parent process gets in an infinite loop never returning.

This commit fixes that by adding a non blocking waitpid() that monitors
the status of the child so it can exit if the child failed.

Acked-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>
---

diff --git a/src/bin/lttng-sessiond/main.c b/src/bin/lttng-sessiond/main.c
index 8aea0e77c..67ecc5228 100644
--- a/src/bin/lttng-sessiond/main.c
+++ b/src/bin/lttng-sessiond/main.c
@@ -4580,6 +4580,18 @@ static int daemonize(void)
 		 * user.
 		 */
 		while (!CMM_LOAD_SHARED(recv_child_signal)) {
+			int status;
+			pid_t ret;
+
+			/*
+			 * Check if child exists without blocking. If so, we have to stop
+			 * this parent process and return an error.
+			 */
+			ret = waitpid(pid, &status, WNOHANG);
+			if (ret < 0 || (ret != 0 && WIFEXITED(status))) {
+				/* The child exited somehow or was not valid. */
+				goto error;
+			}
 			sleep(1);
 		}