Re: [PATCH 1/5] vfork: don't freezer_count() for in-kernel usersof CLONE_VFORK

From: Oleg Nesterov
Date: Sat Feb 16 2013 - 12:07:17 EST

On 02/16, Mandeep Singh Baines wrote:
> We don't need to call freezer_do_not_count() for in-kernel users
> of CLONE_VFORK since exec will get called in bounded time.
> We don't want to call freezer_count() for in-kernel users because
> they may be holding locks. freezer_count() calls try_to_freeze().
> We don't want to freeze an in-kernel user because it may be
> holding locks.

I can only repeat my question ;)

Who? We should not do this anyway. And __call_usermodehelper() doesn't

OK, its caller (process_one_work) does lock_map_acquire() for debugging
purposes, this can "confuse" print_held_locks_bug(). But this thread is

Previously this was needed to suppress the false positive. Now that 2/5
checks PF_NOFREEZE, why do we need this change?

> @@ -722,9 +722,11 @@ static int wait_for_vfork_done(struct task_struct *child,
> {
> int killed;
> - freezer_do_not_count();
> + if (!(current->flags & PF_KTHREAD))
> + freezer_do_not_count();

If I missed something and we really need this, imho this needs a comment.


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