Messages in this thread | | | Subject | Re: [PATCH v15 04/13] task_isolation: add initial support | From | Chris Metcalf <> | Date | Mon, 29 Aug 2016 12:53:30 -0400 |
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On 8/29/2016 12:48 PM, Peter Zijlstra wrote: > On Mon, Aug 29, 2016 at 12:40:32PM -0400, Chris Metcalf wrote: >> On 8/29/2016 12:33 PM, Peter Zijlstra wrote: >>> On Tue, Aug 16, 2016 at 05:19:27PM -0400, Chris Metcalf wrote: >>>> + /* >>>> + * Request rescheduling unless we are in full dynticks mode. >>>> + * We would eventually get pre-empted without this, and if >>>> + * there's another task waiting, it would run; but by >>>> + * explicitly requesting the reschedule, we may reduce the >>>> + * latency. We could directly call schedule() here as well, >>>> + * but since our caller is the standard place where schedule() >>>> + * is called, we defer to the caller. >>>> + * >>>> + * A more substantive approach here would be to use a struct >>>> + * completion here explicitly, and complete it when we shut >>>> + * down dynticks, but since we presumably have nothing better >>>> + * to do on this core anyway, just spinning seems plausible. >>>> + */ >>>> + if (!tick_nohz_tick_stopped()) >>>> + set_tsk_need_resched(current); >>> This is broken.. and it would be really good if you don't actually need >>> to do this. >> Can you elaborate? > Naked use of TIF_NEED_RESCHED like this is busted. There is more state > that needs to be poked to keep things consistent / working.
Would it be cleaner to just replace the set_tsk_need_resched() call with something like:
set_current_state(TASK_INTERRUPTIBLE); schedule(); __set_current_state(TASK_RUNNING);
or what would you recommend?
Or, as I said, just doing a busy loop here while testing to see if need_resched or signal had been set?
-- Chris Metcalf, Mellanox Technologies http://www.mellanox.com
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