linux-kernel - Re: Hibernate stuck after recent kernel/workqueue.c changes in Stable 6.6.23

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Message-ID: <ZgylCe48FuOKNWtM@slm.duckdns.org>
Date: Tue, 2 Apr 2024 14:38:33 -1000
From: Tejun Heo <tj@...nel.org>
To: Linux regressions mailing list <regressions@...ts.linux.dev>
Cc: Greg KH <gregkh@...uxfoundation.org>, Sasha Levin <sashal@...nel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Hibernate stuck after recent kernel/workqueue.c changes in
 Stable 6.6.23

Hello,

On Tue, Apr 02, 2024 at 10:08:11AM +0200, Linux regression tracking (Thorsten Leemhuis) wrote:
> Hi stable team, there is a report that the recent backport of
> 5797b1c18919cd ("workqueue: Implement system-wide nr_active enforcement
> for unbound workqueues") [from Tejun] to 6.6.y (as 5a70baec2294) broke
> hibernate for a user. 6.6.24-rc1 did not fix this problem; reverting the
> culprit does.
> 
> > With kernel 6.6.23 hibernating usually hangs here: the display stays
> > on but the mouse pointer does not move and the keyboard does not work.
> > But SysRq REISUB does reboot. Sometimes it seems to hibernate: the
> > computer powers down and can be waked up and the previous display comes
> > visible, but it is stuck there.
> 
> See https://bugzilla.kernel.org/show_bug.cgi?id=218658 for details.
> Note, you have to use bugzilla to reach the reporter, as I sadly[1] can
> not CCed them in mails like this.
> 
> Side note: there is a mainline report about problems due to
> 5797b1c18919cd ("workqueue: Implement system-wide nr_active enforcement
> for unbound workqueues") as well, but it's about "nohz_full=0 prevents
> kernel from booting":
> https://bugzilla.kernel.org/show_bug.cgi?id=218665; will forward that
> separately to Tejun.
> 
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)

Sorry about late reply but that commit is not for -stable. It does fix an
undesirable behavior from an earlier commit, so it has the Fixes tag but it
has a series of dependencies that need to be backported together which would
be far too invasive for -stable, thus no Cc: stable. I didn't know a Fixes
tag automatically triggers backport to -stable. I will keep that in mind for
future.

Thanks.

-- 
tejun