[PATCH 3.16 013/233] pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes

[Ben Hutchings]

3.16.48-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>

commit b9a985db98961ae1ba0be169f19df1c567e4ffe0 upstream.

The code can potentially sleep for an indefinite amount of time in
zap_pid_ns_processes triggering the hung task timeout, and increasing
the system average.  This is undesirable.  Sleep with a task state of
TASK_INTERRUPTIBLE instead of TASK_UNINTERRUPTIBLE to remove these
undesirable side effects.

Apparently under heavy load this has been allowing Chrome to trigger
the hung time task timeout error and cause ChromeOS to reboot.

Reported-by: Vovo Yang <vovoy@xxxxxxxxxx>
Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Fixes: 6347e9009104 ("pidns: guarantee that the pidns init will be the last pidns process reaped")
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 kernel/pid_namespace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -234,7 +234,7 @@ void zap_pid_ns_processes(struct pid_nam
 	 * Make sure they all go away, see free_pid().
 	 */
 	for (;;) {
-		set_current_state(TASK_UNINTERRUPTIBLE);
+		set_current_state(TASK_INTERRUPTIBLE);
 		if (pid_ns->nr_hashed == init_pids)
 			break;
 		schedule();