Messages in this thread | | | Date | Thu, 27 Nov 2014 17:56:37 -0500 | From | Dave Jones <> | Subject | Re: frequent lockups in 3.18rc4 |
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On Thu, Nov 27, 2014 at 11:17:16AM -0800, Linus Torvalds wrote: > On Wed, Nov 26, 2014 at 2:57 PM, Dave Jones <davej@redhat.com> wrote: > > > > So 3.17 also has this problem. > > Good news I guess in that it's not a regression, but damn I really didn't > > want to have to go digging through the mists of time to find the last 'good' point. > > So I'm looking at the watchdog code, and it seems racy wrt parking and startup. > > In particular, it sets the high priority *after* starting the hrtimer, > and it goes back to SCHED_NORMAL *before* canceling the timer. > > Which seems completely ass-backwards. And the smp_hotplug_thread stuff > explicitly enables preemption around the setup/cleanup/part/unpark > operations. > > However, that would be an issue only if trinity might be doing things > that enable and disable the watchdog. And doing so under insane loads. > Even then it seems unlikely. > > The insane loads you have. But even then, could a load average of 169 > possibly delay running a non-RT process for 22 seconds? Doubtful. > > But just in case: do you do cpu hotplug events (that will disable and > re-enable the watchdog process?). Anything else that will part/unpark > the hotplug thread?
That's root-only iirc, and I'm not running trinity as root, so that shouldn't be happening. There's also no sign of such behaviour in dmesg when the problem occurs.
> Quite frankly, I'm just grasping for straws here, but a lot of the > watchdog traces really have seemed spurious...
Agreed.
Currently leaving 3.16 running. 21hrs so far.
Dave
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