lkml.org 
[lkml]   [2014]   [Nov]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: frequent lockups in 3.18rc4
    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



    \
     
     \ /
      Last update: 2014-11-28 00:41    [W:4.074 / U:0.172 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site