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Date: Fri, 19 Sep 2014 13:47:34 +0200 From: Daniel Wagner <daniel.wagner@...-carit.de> To: Juri Lelli <juri.lelli@....com>, <peterz@...radead.org> CC: <mingo@...hat.com>, <juri.lelli@...il.com>, <raistlin@...ux.it>, <michael@...rulasolutions.com>, <fchecconi@...il.com>, <vincent@...out.info>, <luca.abeni@...tn.it>, <linux-kernel@...r.kernel.org>, Li Zefan <lizefan@...wei.com>, <cgroups@...r.kernel.org> Subject: Re: [PATCH 2/3] sched/deadline: fix bandwidth check/update when migrating tasks between exclusive cpusets Hi, On 09/19/2014 11:22 AM, Juri Lelli wrote: > Exclusive cpusets are the only way users can restrict SCHED_DEADLINE tasks > affinity (performing what is commonly called clustered scheduling). > Unfortunately, such thing is currently broken for two reasons: > > - No check is performed when the user tries to attach a task to > an exlusive cpuset (recall that exclusive cpusets have an > associated maximum allowed bandwidth). > > - Bandwidths of source and destination cpusets are not correctly > updated after a task is migrated between them. > > This patch fixes both things at once, as they are opposite faces > of the same coin. > > The check is performed in cpuset_can_attach(), as there aren't any > points of failure after that function. The updated is split in two > halves. We first reserve bandwidth in the destination cpuset, after > we pass the check in cpuset_can_attach(). And we then release > bandwidth from the source cpuset when the task's affinity is > actually changed. Even if there can be time windows when sched_setattr() > may erroneously fail in the source cpuset, we are fine with it, as > we can't perfom an atomic update of both cpusets at once. > > Reported-by: Daniel Wagner <daniel.wagner@...-carit.de> Ack I have no special test for this, I just let my test running which was fixed by patch #1. Works fine though. I'll plan to write some test for this. Thanks, Daniel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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