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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>
This commit is contained in:
Tejun Heo 2011-11-21 12:32:23 -08:00
parent a5be2d0d1a
commit a585042f7b
2 changed files with 2 additions and 4 deletions
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3
kernel/exit.c
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@ -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". */

3
kernel/power/process.c
View File

@ -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;
}