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Commit a585042f authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
parent a5be2d0d

kernel/exit.c

+1 −2
Original line number Diff line number Diff line
@@ -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".  */

kernel/power/process.c

+1 −2
Original line number Diff line number Diff line
@@ -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;

}