linux-kernel - Re: Are jump labels broken on 6.11-rc1?

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Message-ID: <20240919234146.GH182177@frogsfrogsfrogs>
Date: Thu, 19 Sep 2024 16:41:46 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Chandan Babu R <chandanbabu@...nel.org>,
	Matthew Wilcox <willy@...radead.org>,
	xfs <linux-xfs@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>, x86@...nel.org
Subject: Re: Are jump labels broken on 6.11-rc1?

On Mon, Sep 16, 2024 at 09:08:01AM -0700, Darrick J. Wong wrote:
> On Thu, Sep 05, 2024 at 11:16:05AM +0200, Peter Zijlstra wrote:
> > On Thu, Sep 05, 2024 at 10:12:41AM +0200, Peter Zijlstra wrote:
> > > On Mon, Aug 26, 2024 at 08:35:06PM -0700, Darrick J. Wong wrote:
> > 
> > > > [33965.988873] ------------[ cut here ]------------
> > > > [33966.013870] WARNING: CPU: 1 PID: 8992 at kernel/jump_label.c:295 __static_key_slow_dec_cpuslocked.part.0+0xb0/0xc0
> > 
> > > > [33966.040184] pc : __static_key_slow_dec_cpuslocked.part.0+0xb0/0xc0
> > > > [33966.042845] lr : __static_key_slow_dec_cpuslocked.part.0+0x48/0xc0
> > 
> > > > [33966.072840] Call trace:
> > > > [33966.073838]  __static_key_slow_dec_cpuslocked.part.0+0xb0/0xc0
> > > > [33966.076105]  static_key_slow_dec+0x48/0x88
> > 
> > > > This corresponds to the:
> > > > 
> > > > 	WARN_ON_ONCE(!static_key_slow_try_dec(key));
> > > 
> > > But but but,... my patch killed that function. So are you sure it is
> > > applied ?!
> > > 
> > > Because this sounds like exactly that issue again.
> > > 
> > > Anyway, it appears I had totally forgotten about this issue again due to
> > > holidays, sorry. Let me stare hard at Thomas' patch and make a 'pretty'
> > > one that does boot.
> > 
> > I've taken tglx's version with a small change (added comment) and boot
> > tested it and queued it here:
> > 
> >   git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/urgent
> > 
> > Could you please double check on both x86_64 and arm64?
> 
> Will send this out on the test farm tonight, thanks for the patch.
> 
> > If green by with the build robots and your own testing I'll push this
> > into tip/locking/urgent to be sent to Linus on Sunday. Hopefully finally
> > resolving this issue.
> 
> Sorry I didn't get to this earlier; I've been on vacation since the end
> of August.  Now to get to the ~1300 fsdevel emails... ;)

After 3.5 days of continuous pounding on the jump labels I haven't seen
any complaints from the kernel, so consider commit 6b01e5a8c11611
("jump_label: Fix static_key_slow_dec() yet again")

Tested-by: Darrick J. Wong <djwong@...nel.org>

Thanks for your help!

--D

> --D
>