Messages in this thread | | | Date | Fri, 8 Sep 2017 16:43:07 +0200 | From | Maxime Ripard <> | Subject | Re: mutex_lock issues during poweroff |
| |
Hi Peter,
Thanks for your answer.
On Thu, Sep 07, 2017 at 02:40:33PM +0200, Peter Zijlstra wrote: > On Thu, Sep 07, 2017 at 02:16:19PM +0200, Maxime Ripard wrote: > > One thing worth noting is that we couldn't reproduce the issue with a > > 4.13. We can't bisect really easily due to the amount of patches that > > we still have on 4.9 and have all been merged since, but it seems like > > the bug was fixed (either on purpose or as a side effect), and was > > never sent to stable. Looking at the history of kernel/locking/mutex.c > > during that window didn't really show anything obvious though. > > > > If you have any ideas or spot something very wrong, I'd be happy to > > hear about. Thanks! > > Well, we did a _complete_ rewrite of the mutex primitive in v4.10-rc1.
Ok.
What commit happened to be the rewrite? 9d659ae14b54 ("locking/mutex: Add lock handoff to avoid starvation") ? We backported this one and 3ca0ff571b09 ("locking/mutex: Rework mutex::owner"), and still can reproduce the issue. Is there any other?
> Part of the reason for that rewrite was fixing a starvation case, but > for that you'd need to actually have contending usage, which you claim > not to have.
Yeah, we're close to the opposite case :)
> Aside from that I really can't remember any specific issues with the old > code (4.9 is such a long time ago). You could try to disable the > optimistic spinning code, see if that helps. > > You did also say you were running on an ARM64, there were a few memory > ordering fixes like for example commit: > > 50972fe78f24 ("locking/osq_lock: Fix osq_lock queue corruption")
We're running on ARM, not ARM64 (they still are separate architectures under arch/, unlike x86), but I'll look into them too.
Thanks! Maxime
-- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com [unhandled content-type:application/pgp-signature] | |