Messages in this thread | | | Date | Mon, 17 Nov 2014 21:09:59 -0500 | From | Dave Jones <> | Subject | Re: frequent lockups in 3.18rc4 |
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On Mon, Nov 17, 2014 at 11:59:34AM -0800, Linus Torvalds wrote: > On Mon, Nov 17, 2014 at 9:03 AM, Dave Jones <davej@redhat.com> wrote: > > > > It could a completely different cause for lockup, but seeing this now > > has me wondering if perhaps it's something unrelated to the kernel. > > I have recollection of running late .17rc's for days without incident, > > and I'm pretty sure .17 was ok too. But a few weeks ago I did upgrade > > that test box to the Fedora 21 beta. Which means I have a new gcc. > > I'm not sure I really trust 4.9.1 yet, so maybe I'll see if I can > > get 4.8 back on there and see if that's any better. > > I'm not sure if I should be relieved or horrified. > > Horrified, I think. > > It really would be a wonderful thing to have some kind of "compiler > bisection" with mixed object files to see exactly which file it > miscompiles (and by "miscompiles" it might just be a kernel bug where > we are missing a barrier or something, and older gcc's just happened > to not show it - so it could still easily be a kernel problem).
After wasting countless hours rolling back to Fedora 20 and gcc 4.8.1, I saw the exact same trace on 3.17, so now I don't know what to think.
So it's great that it's not a regression vs .17, but otoh, who knows how far back this goes. This looks like a nightmarish bisect case, and I've no idea why it's now happening so often.
I'll give Don's softlockup_all_cpu_backtrace=1 idea a try on 3.18rc5 and see if that shines any more light on this.
Deeply puzzling.
Dave
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