Messages in this thread | | | Date | Wed, 7 Oct 2009 12:37:41 +0900 | Subject | Re: [PATCH 2/2] mlock use lru_add_drain_all_async() | From | KOSAKI Motohiro <> |
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2009/10/7 Christoph Lameter <cl@linux-foundation.org>: > On Tue, 6 Oct 2009, KOSAKI Motohiro wrote: > >> Suppose you have 2 cpus, cpu1 is busy doing a SCHED_FIFO-99 while(1), >> cpu0 does mlock()->lru_add_drain_all(), which does >> schedule_on_each_cpu(), which then waits for all cpus to complete the >> work. Except that cpu1, which is busy with the RT task, will never run >> keventd until the RT load goes away. >> >> This is not so much an actual deadlock as a serious starvation case. >> >> Actually, mlock() doesn't need to wait to finish lru_add_drain_all(). >> Thus, this patch replace it with lru_add_drain_all_async(). > > Ok so this will queue up lots of events for the cpu doing a RT task. If > the RT task is continuous then they will be queued there forever?
Yes. this patch solved very specific issue only. In original bug-report case, the system has two cpuset and the RT task own one cpuset as monopoly. Thus, your worried thing doesn't occur.
Perhaps, we need complete solution. but I don't think this patch have bad side effect. then, I hope to push it into mainline. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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