Messages in this thread | | | Date | Sat, 16 Oct 2010 17:27:36 +0200 | Subject | Re: [REGRESSION] um: rcu_sched_state detected stall on CPU 0 | From | richard -rw- weinberger <> |
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On Fri, Oct 15, 2010 at 9:48 AM, Peter Zijlstra <peterz@infradead.org> wrote: > On Fri, 2010-10-15 at 10:02 +0300, Pekka Enberg wrote: >> On Fri, Oct 15, 2010 at 2:44 AM, richard -rw- weinberger >> <richard.weinberger@gmail.com> wrote: >> > On Thu, Oct 14, 2010 at 9:50 PM, Arjan van de Ven >> <arjan@linux.intel.com> wrote: >> >> On 10/14/2010 11:27 AM, richard -rw- weinberger wrote: >> >>> >> >>> Hi Arjan! >> >>> >> >>> This commit causes some problems on UML. >> >>> >> >> that is extremely weird. >> >>> >> >>> The kernel freezes after a few seconds until it gets some input. >> >>> e.g: When I run top it stops refreshing the process list until i >> press a >> >>> button. >> >> >> >> a slab timer change (to not be as critical) causing global timer >> issues.... >> >> that's very obviously not a problem with this patch. >> >> has this been seem anywhere except UML ? >> > >> > A small update: >> > It seems that CONFIG_NO_HZ is broken on UML. :-( >> > >> > CONFIG_NO_HZ + CONFIG_SLAB: works >> > CONFIG_NO_HZ + CONFIG_SLAB + your patch: broken >> > CONFIG_NO_HZ + CONFIG_SLUB: broken >> > >> > CONFIG_SLAB + your patch: works >> > CONFIG_SLAB: works >> > CONFIG_SLUB: works >> >> Thanks for testing! Thomas, Ingo, Peter, I'm not sure who maintains >> CONFIG_NO_HZ so I CC'd you. The problem here is that Arjan's >> deferrable timers patch in SLAB triggered something that looks like a >> latent bug with UML and NOHZ. > > Thomas does mostly, but if its UML specific, I guess its Jeff Dike > you'll be wanting to talk to, since he's the arch maintainer.
After reviewing the code for hours I've found the bug. It's a int/long long issue within arch/um/os-Linux/time.c. A patch is on the way!
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