Messages in this thread | | | Date | Mon, 5 Dec 2011 21:28:22 +1100 | From | Anton Blanchard <> | Subject | Re: [PATCH 2/2] watchdog: Softlockup has regular windows where it is not armed |
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Hi Don,
> > There might be a reason for this two stage sync but I haven't been > > able to find it yet. Perhaps the unsynced versions of cpu_clock() > > and sched_clock_tick() are not safe to call from all contexts? > > According to commit 8c2238eaaf0f774ca0f8d9daad7a616429bbb7f1 that was > the case, cpu_clock wasn't NMI-safe. Now it is, thanks to Peter.
Thanks, that makes sense now.
> I have a couple of concerns about the patch. I am wondering about the > overhead of getting the timestamp more often now as opposed to just > setting a boolean for later. It makes sense to stamp it at the time > of the call, don't know what the cost is.
I had a similar concern since we do execute this quite a lot. The overhead of cpu_clock is quite low on powerpc, but not sure about the other architectures.
> I am also concern about how this affects suspend/resume and kgdb. I > cc'd Jason above for kgdb. I'll have to run some tests locally to > see what long periods of delay look like. Oh and virt guests too. > You don't have any test results from that setup do you?
I haven't tested suspend resume, kgdb or virtual guests yet.
Anton
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