From 5fcc57f2d5d558056668159f9153bf21d2c53d16 Mon Sep 17 00:00:00 2001 From: Gautham R Shenoy Date: Wed, 23 May 2007 13:57:28 -0700 Subject: [PATCH] freezer: fix PF_NOFREEZE vs freezeable race This patch fixes the race pointed out by Oleg Nesterov. * Freezer marks a thread as freezeable. * The thread now marks itself PF_NOFREEZE, but it will be frozen on on calling try_to_freeze(). Thus the task is frozen, even though it doesn't want to. * Subsequent thaw_processes() will also fail to thaw the task since it is marked PF_NOFREEZE. Avoid this problem by checking the task's PF_NOFREEZE status in frozen_processes() before marking the task as frozen. Signed-off-by: Gautham R Shenoy Signed-off-by: Rafael J. Wysocki Cc: Oleg Nesterov Cc: Pavel Machek Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/freezer.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/include/linux/freezer.h b/include/linux/freezer.h index c9435252e8e..1045ee9c0bb 100644 --- a/include/linux/freezer.h +++ b/include/linux/freezer.h @@ -63,8 +63,10 @@ static inline int thaw_process(struct task_struct *p) */ static inline void frozen_process(struct task_struct *p) { - p->flags |= PF_FROZEN; - wmb(); + if (!unlikely(p->flags & PF_NOFREEZE)) { + p->flags |= PF_FROZEN; + wmb(); + } clear_tsk_thread_flag(p, TIF_FREEZE); } -- 2.41.1