Messages in this thread | | | Subject | Re: [PATCH v4] softlockup: remove hung_task_check_count | From | Peter Zijlstra <> | Date | Wed, 28 Jan 2009 09:25:00 +0100 |
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On Tue, 2009-01-27 at 10:48 -0800, Mandeep Singh Baines wrote: > Ingo Molnar (mingo@elte.hu) wrote: > > > > * Mandeep Singh Baines <msb@google.com> wrote: > > > > > The design was proposed by Frédéric Weisbecker. Peter Zijlstra suggested > > > the use of RCU. > > > > ok, this looks _much_ cleaner. > > > > One question: > > > > > - read_lock(&tasklist_lock); > > > + rcu_read_lock(); > > > do_each_thread(g, t) { > > > - if (!--max_count) > > > + if (need_resched()) > > > goto unlock; > > > > Isnt it dangerous to skip a check just because we got marked for > > reschedule? Since it runs so rarely it could by accident be preempted and > > we'd not get any checking done for a long time. > > > > Yeah, the checking could be deferred indefinitely. So you could have a system > where tasks are hung but it takes a really long time to detect this and > finally panic the system. Not so good for high-availability.
Why break out at all? Are you that worried about khungtaskd introducing latencies? Is using preemptible RCU an option for you?
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