Messages in this thread | | | Date | Tue, 2 Sep 2014 21:08:31 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: Race condition in HR timers that cause double insertion and hard lockup -- all latest versions |
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On Tue, 2 Sep 2014, Linus Torvalds wrote:
> On Tue, Sep 2, 2014 at 8:45 AM, Itzcak Pechtalt > <itzcak@flashnetworks.com> wrote: > > > > I opened a bug in https://bugzilla.kernel.org/show_bug.cgi?id=83601 for this subject with full description. > > There is also a short fix patch for kernel/hrtimer.c file. > > Even if this bug occurs rary, however it resolves system hard lockup option. > > The patch is whitespace-damaged, but with a small oneliner like this > that doesn't much matter (the timer files moved to kernel/time/ during > this merge window, so the patch wouldn't apply as-is anyway). > > It needs a sign-off (see Documentation/SubmittingPatches), but even > more importantly it needs to go to the right people for > double-checking. > > But the patch is more broken than whitespace and even lack of > sign-off. It cannot even have compiled. I'm assuming "timer_state" was > intended to be "timer->state". Also, every caller but one already has > "HRTIMER_STATE_CALLBACK" set unconditionally or to the old state in > "newstate", so I suspect if this patch is the real fix (which I'll > leave for Thomas to comment more on), afaik the actual problem can > only happen through migrate_hrtimer_list() which uconditionally sets > the whole state to HRTIMER_STATE_MIGRATE. > > Thomas? Leaving damaged patch quoted below.
Right. It's been fixed long ago and the migrate path cannot suffer from this problem because at this point a callback running on the dead cpu would cause the
BUG_ON(hrtimer_callback_running(timer));
a few lines above the remove_hrtimer() call to trigger and send the machine into lala land.
Thanks,
tglx
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