Re: [PATCH 5.15 00/92] 5.15.126-rc1 review

[Joel Fernandes]

On Wed, Aug 9, 2023 at 4:38 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> On 8/9/23 13:14, Joel Fernandes wrote:
> > On Wed, Aug 09, 2023 at 12:25:48PM -0700, Guenter Roeck wrote:
> >> On Wed, Aug 09, 2023 at 02:35:59PM -0400, Joel Fernandes wrote:
> >>> On Wed, Aug 9, 2023 at 12:18 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> >>>>
> >>>> On 8/9/23 06:53, Joel Fernandes wrote:
> >>>>> On Wed, Aug 09, 2023 at 12:40:36PM +0200, Greg Kroah-Hartman wrote:
> >>>>>> This is the start of the stable review cycle for the 5.15.126 release.
> >>>>>> There are 92 patches in this series, all will be posted as a response
> >>>>>> to this one.  If anyone has any issues with these being applied, please
> >>>>>> let me know.
> >>>>>>
> >>>>>> Responses should be made by Fri, 11 Aug 2023 10:36:10 +0000.
> >>>>>> Anything received after that time might be too late.
> >>>>>>
> >>>>>> The whole patch series can be found in one patch at:
> >>>>>>       https://www.kernel.org/pub/linux/kernel/v5.x/stable-review/patch-5.15.126-rc1.gz
> >>>>>> or in the git tree and branch at:
> >>>>>>       git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.15.y
> >>>>>> and the diffstat can be found below.
> >>>>>
> >>>>> Not necesscarily new with 5.15 stable but 3 of the 19 rcutorture scenarios
> >>>>> hang with this -rc: TREE04, TREE07, TASKS03.
> >>>>>
> >>>>> 5.15 has a known stop machine issue where it hangs after 1.5 hours with cpu
> >>>>> hotplug rcutorture testing. Me and tglx are continuing to debug this. The
> >>>>> issue does not show up on anything but 5.15 stable kernels and neither on
> >>>>> mainline.
> >>>>>
> >>>>
> >>>> Do you by any have a crash pattern that we could possibly use to find the crash
> >>>> in ChromeOS crash logs ? No idea if that would help, but it could provide some
> >>>> additional data points.
> >>>
> >>> The pattern shows as a hard hang, the system is unresponsive and all CPUs
> >>> are stuck in stop_machine. Sometimes it recovers on its own from the
> >>> hang and then RCU immediately gives stall warnings. It takes 1.5 hour
> >>> to reproduce and sometimes never happens for several hours.
> >>>
> >>> It appears related to CPU hotplug since gdb showed me most of the CPUs
> >>> are spinning in multi_cpu_stop() / stop machine after the hang.
> >>>
> >>
> >> Hmm, we do see lots of soft lockups with multi_cpu_stop() in the backtrace,
> >> but not with v5.15.y but with v5.4.y. The actual hang is in stop_machine_yield().
> >
> > Interesting. It looks similar as far as the stack dump in gdb goes, here are
> > the stacks I dumped with the hang I referred to:
> > https://paste.debian.net/1288308/
> >
>
> That link gives me "Entry not found".

Yeah that was weird. Here it is again: https://pastebin.com/raw/L3nv1kH2