Messages in this thread | | | Date | Tue, 23 Oct 2012 17:39:19 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/7] freezer: add missing mb's to freezer_count() and freezer_should_skip() |
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Hi Tejun,
On 10/22, Tejun Heo wrote: > > On Mon, Oct 22, 2012 at 07:44:04PM +0200, Oleg Nesterov wrote: > > > We probably have another similar race. If ptrace_stop()->may_ptrace_stop() > > returns false, the task does > > > > __set_current_state(TASK_RUNNING); > > // no mb in between > > try_to_freeze(); > > > > And this can race with task_is_stopped_or_traced() check in the same way. > > (of course this is only theoretical). > > > > do_signal_stop() is probably fine, we can rely on ->siglock. > > Hmm.... Guess we should drop __ from set_current_state.
Yes.
Or we can change ptrace_stop() and do_signal_stop() to use freezer_do_not_count/ freezer_count and remove task_is_stopped_or_traced() from update_if_frozen() and try_to_freeze_tasks(). But this means that do_signal_stop() will call try_to_freeze() twice, unless we add __freezer_count() which only clears PF_FREEZER_SKIP.
> I wonder > whether we should just add mb to freezing()? What do you think?
Yes, I thought about this too. I just do not know what would be better.
Oleg.
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