Patch "coredump: fix unfreezable coredumping task" has been added to the 4.8-stable tree

This is a note to let you know that I've just added the patch titled

coredump: fix unfreezable coredumping task

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
coredump-fix-unfreezable-coredumping-task.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Andrey Ryabinin <[email protected]>
Date: Thu, 10 Nov 2016 10:46:38 -0800
Subject: coredump: fix unfreezable coredumping task

From: Andrey Ryabinin <[email protected]>

commit 70d78fe7c8b640b5acfad56ad341985b3810998a upstream.

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.

---
 fs/coredump.c |    3 +++
 1 file changed, 3 insertions(+)

@@ -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,
 	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

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/coredump-fix-unfreezable-coredumping-task.patch