From: Peter Zijlstra <peterz@infradead•org>
To: Heiko Carstens <hca@linux•ibm.com>
Cc: Mikhail Zaslonko <zaslonko@linux•ibm.com>,
linux-next@vger•kernel.org, linux-s390@vger•kernel.org,
Ingo Molnar <mingo@kernel•org>,
Alexander Egorenkov <egorenar@linux•ibm.com>,
Thomas Gleixner <tglx@kernel•org>,
"Paul E. McKenney" <paulmck@kernel•org>
Subject: Re: [linux-next][s390] Boot hang after merge c50f05bd3c4e (sched/hrtick)
Date: Thu, 5 Mar 2026 13:12:01 +0100 [thread overview]
Message-ID: <20260305121201.GB596554@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20260305074922.7170Ad3-hca@linux.ibm.com>
On Thu, Mar 05, 2026 at 08:49:22AM +0100, Heiko Carstens wrote:
> On Wed, Mar 04, 2026 at 05:13:56PM +0100, Mikhail Zaslonko wrote:
> > Sorry, forgot to Cc a few people.
> > Adding scheduler maintainers.
> >
> > Thanks,
> > Mikhail Zaslonko
> >
> > On 03-Mar-26 19:31, Mikhail Zaslonko wrote:
> > > Hello,
> > >
> > > we have kernel-next boot hang on s390 starting next-20260302.
> > >
> > > I bisected it in linux-next to:
> > >
> > > c50f05bd3c4e ("Merge branch into tip/master: 'sched/hrtick'")
> > >
> > > Good:
> > > 72a2ab46f045
> > > d50da4b5915f (2nd parent: sched/hrtick branch)
> > >
> > > Bad:
> > > c50f05bd3c4e (merge commit)
> > >
> > > Environment:
> > > - s390 under z/VM
> > > - many CPUs defined (32+)
> > > - boot hangs early with RCU stall (see boot log excerpt below)
>
> linux-next is currently completely broken because of this.
Turns out, that aside from something weird with ACPI PCI routing, these
two patches:
https://lkml.kernel.org/r/87bjh4zies.ffs@tglx
https://lkml.kernel.org/r/87cy1jsa4m.ffs@tglx
Make tip/sched/core, which includes:
1b8b1bb2a2fa (tip/sched/core) Merge branch 'linus' into sched/core, to resolve conflicts
c1455a120f7e Merge branch 'sched/hrtick'
work reliably on my SPR. But since you don't have
CLOCK_SOURCE_HAS_COUPLED_CLOCK_EVENT (yet) this should not affect you.
> Any idea?
Well, that all looks like timers are going missing. Which matches with
Sven saying that disabling HRTIMER_REARM_DEFERRED makes it go again.
I'm just not sure I can see why things would break between
sched/hrtick (GOOD) and 1b8b1bb2a2fa (BAD).
Looking at the diff (eg git diff d50da4b5915f..c50f05bd3c4e) show some
idle time changes to s390 and various kernel/ changes, but nothing that
stands out to me :/
next prev parent reply other threads:[~2026-03-05 12:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-03 18:31 [linux-next][s390] Boot hang after merge c50f05bd3c4e (sched/hrtick) Mikhail Zaslonko
2026-03-04 16:13 ` Mikhail Zaslonko
2026-03-05 7:49 ` Heiko Carstens
2026-03-05 12:12 ` Peter Zijlstra [this message]
2026-03-05 12:35 ` Peter Zijlstra
2026-03-05 12:45 ` Peter Zijlstra
2026-03-05 13:07 ` Peter Zijlstra
2026-03-05 15:02 ` Heiko Carstens
2026-03-05 17:24 ` Mikhail Zaslonko
2026-03-05 19:48 ` Heiko Carstens
2026-03-06 8:41 ` Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20260305121201.GB596554@noisy.programming.kicks-ass.net \
--to=peterz@infradead$(echo .)org \
--cc=egorenar@linux$(echo .)ibm.com \
--cc=hca@linux$(echo .)ibm.com \
--cc=linux-next@vger$(echo .)kernel.org \
--cc=linux-s390@vger$(echo .)kernel.org \
--cc=mingo@kernel$(echo .)org \
--cc=paulmck@kernel$(echo .)org \
--cc=tglx@kernel$(echo .)org \
--cc=zaslonko@linux$(echo .)ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox