linux-kernel - [PATCH] coredump: fix unfreezable coredumping task

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Date:   Fri, 30 Sep 2016 11:50:34 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Alexander Viro <viro@...iv.linux.org.uk>,
        Tejun Heo <tj@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Pavel Machek <pavel@....cz>, "Oleg Nesterov" <oleg@...hat.com>
CC:     <linux-pm@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        <stable@...r.kernel.org>
Subject: [PATCH] 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'.

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

Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc: stable@...r.kernel.org
---
 fs/coredump.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/coredump.c b/fs/coredump.c
index 281b768..eb9c92c 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -1,6 +1,7 @@
 #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
-- 
2.7.3