freezer: remove racy clear_freeze_flag() and set PF_NOFREEZE on dead tasks (a585042f) · Commits · 戴 / test

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

+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;
		}

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