Commit 70d78fe7 authored Nov 10, 2016 by Andrey Ryabinin Committed by Linus Torvalds Nov 11, 2016

coredump: fix unfreezable coredumping task

It could be not possible to freeze coredumping task when it waits for
'core_state->startup' completion, because threads are frozen in
get_signal() before they got a chance to complete 'core_state->startup'.

Inability to freeze a task during suspend will cause suspend to fail.
Also CRIU uses cgroup freezer during dump operation.  So with an
unfreezable task the CRIU dump will fail because it waits for a
transition from 'FREEZING' to 'FROZEN' state which will never happen.

Use freezer_do_not_count() to tell freezer to ignore coredumping task
while it waits for core_state->startup completion.

Link: http://lkml.kernel.org/r/1475225434-3753-1-git-send-email-aryabinin@virtuozzo.com


Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Tejun Heo <tj@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 60da81ea

fs/coredump.c

+3 −0

Original line number	Diff line number	Diff line
		#include <linux/slab.h>
		#include <linux/file.h>
		#include <linux/fdtable.h>
		#include <linux/freezer.h>
		#include <linux/mm.h>
		#include <linux/stat.h>
		#include <linux/fcntl.h>
		@@ -423,7 +424,9 @@ static int coredump_wait(int exit_code, struct core_state *core_state)
		if (core_waiters > 0) {
		struct core_thread *ptr;

		freezer_do_not_count();
		wait_for_completion(&core_state->startup);
		freezer_count();
		/*
		* Wait for all the threads to become inactive, so that
		* all the thread context (extended register state, like

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