ACK: [PATCH 1/1][Y/Z SRU] pid_ns: Sleep in TASK_INTERRUPTIBLE in zap_pid_ns_processes

[Colin Ian King]

On 19/06/17 14:02, Seth Forshee wrote:
> From: "Eric W. Biederman" <ebiederm at xmission.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1698264
> 
> 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)
> Signed-off-by: Seth Forshee <seth.forshee at canonical.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 a65ba137fd15..567ecc826bc8 100644
> --- a/kernel/pid_namespace.c
> +++ b/kernel/pid_namespace.c
> @@ -255,7 +255,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
>  	 * if reparented.
>  	 */
>  	for (;;) {
> -		set_current_state(TASK_UNINTERRUPTIBLE);
> +		set_current_state(TASK_INTERRUPTIBLE);
>  		if (pid_ns->nr_hashed == init_pids)
>  			break;
>  		schedule();
> 

Clean upstream cherry pick, test results look good.

Acked-by: Colin Ian King <colin.king at canonical.com>