From a585042f7b933539a0b6bc63650c2d49ffb2e55d Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 21 Nov 2011 12:32:23 -0800
Subject: [PATCH] freezer: remove racy clear_freeze_flag() and set PF_NOFREEZE
on dead tasks
clear_freeze_flag() in exit_mm() is racy. Freezing can start
afterwards. Remove it. Skipping freezer for exiting task will be
properly implemented later.
Also, freezable() was testing exit_state directly to make system
freezer ignore dead tasks. Let the exiting task set PF_NOFREEZE after
entering TASK_DEAD instead.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
---
kernel/exit.c | 3 +--
kernel/power/process.c | 3 +--
2 files changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/exit.c b/kernel/exit.c
index d0b7d988f873..95a4141d07e7 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -679,8 +679,6 @@ static void exit_mm(struct task_struct * tsk)
tsk->mm = NULL;
up_read(&mm->mmap_sem);
enter_lazy_tlb(mm, current);
- /* We don't want this task to be frozen prematurely */
- clear_freeze_flag(tsk);
task_unlock(tsk);
mm_update_next_owner(mm);
mmput(mm);
@@ -1040,6 +1038,7 @@ NORET_TYPE void do_exit(long code)
exit_rcu();
/* causes final put_task_struct in finish_task_switch(). */
tsk->state = TASK_DEAD;
+ tsk->flags |= PF_NOFREEZE; /* tell freezer to ignore us */
schedule();
BUG();
/* Avoid "noreturn function does return". */
diff --git a/kernel/power/process.c b/kernel/power/process.c
index fe2787207f00..23822dc14b6c 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -25,8 +25,7 @@
static inline int freezable(struct task_struct * p)
{
if ((p == current) ||
- (p->flags & PF_NOFREEZE) ||
- (p->exit_state != 0))
+ (p->flags & PF_NOFREEZE))
return 0;
return 1;
}
--
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