Messages in this thread | | | Date | Wed, 25 Aug 2010 09:56:03 +0800 | Subject | Re: [RFC PATCH 1/3] timer: fix comments of try_to_del_timer_sync() | From | Yong Zhang <> |
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On Wed, Aug 25, 2010 at 12:31 AM, Oleg Nesterov <oleg@redhat.com> wrote: > Ah, indeed, I forgot. This was another reason for the comment. > >> > Please remove "#ifdef CONFIG_SMP" from set_running_timer(), then iirc >> > it can be used from irq. >> >> I have noticed your comments in the commit log, but I think it's about >> introducing the same semantic of try_to_del_timer_sync() on UP as well >> as SMP. But this patch is focusing on the current code(SMP special). >> Not about realizing try_to_del_timer_sync() on UP case. Do we need >> to do that? > > I dunno. > > But look, currently try_to_del_timer_sync() is not allowed from interrupt > even if it works with CONFIG_SMP. > > If we "officially" allow it to use from irq, it should work on UP too
OK. I see.
> but > it doesn't. del_timer() can't hang, but it can never return -1 to indicate > we hit the running timer. > > Consider: > > // runs in interrup context > > if (try_do_del_timer_sync(&TIMER) > 0) > kfree(something_which_can_be_used_by_TIMER_func); > > This is unsafe on UP.
You are right. It's unsafe here.
I will try to update this patch which introduce try_do_del_timer_sync() on UP case.
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