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. -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
