[Devel] [PATCH rh7] ms/coredump: fix unfreezable coredumping task

[Andrey Ryabinin]

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.

https://jira.sw.ru/browse/PSBM-52793

Link: http://lkml.kernel.org/r/1475225434-3753-1-git-send-email-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
Cc: stable at vger.kernel.org
Acked-by: Oleg Nesterov <oleg at redhat.com>
Acked-by: Pavel Machek <pavel at ucw.cz>
---
 fs/coredump.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/coredump.c b/fs/coredump.c
index e3fdee2..f6a1012 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>
@@ -388,7 +389,9 @@ 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