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

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Message-ID: <20240905091605.GE4928@noisy.programming.kicks-ass.net>
Date: Thu, 5 Sep 2024 11:16:05 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: "Darrick J. Wong" <djwong@...nel.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 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?

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.