[Devel] [PATCH RHEL7 COMMIT] ms/pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-514.16.1.vz7.32.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-514.16.1.vz7.32.4
------>
commit b0fced9b3f46ec4757058d7b0035f173012b49a7
Author: Eric W. Biederman <ebiederm at xmission.com>
Date:   Thu May 11 18:21:01 2017 -0500

    ms/pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes
    
    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 at google.com>
    Reported-by: Guenter Roeck <linux at roeck-us.net>
    Tested-by: Guenter Roeck <linux at roeck-us.net>
    Fixes: 6347e9009104 ("pidns: guarantee that the pidns init will be the last pidns process reaped")
    Cc: stable at vger.kernel.org
    Signed-off-by: "Eric W. Biederman" <ebiederm at xmission.com>
    (cherry picked from commit b9a985db98961ae1ba0be169f19df1c567e4ffe0)
    
    =======================================================
    This patch by Eric W. Biederman will go to 4.12-rc2:
    https://www.spinics.net/lists/linux-containers/msg32521.html
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 kernel/pid_namespace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 594167d..028e864 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -241,7 +241,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 	 * 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();