Re: Are jump labels broken on 6.11-rc1?

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Jul 30, 2024 at 05:19:50PM -0700, Darrick J. Wong wrote:
> On Tue, Jul 30, 2024 at 03:26:26PM +0200, Peter Zijlstra wrote:
> > On Tue, Jul 30, 2024 at 01:00:02PM +0530, Chandan Babu R wrote:
> > > On Mon, Jul 29, 2024 at 08:38:49 PM -0700, Darrick J. Wong wrote:
> > > > Hi everyone,
> > > >
> > > > I got the following splat on 6.11-rc1 when I tried to QA xfs online
> > > > fsck.  Does this ring a bell for anyone?  I'll try bisecting in the
> > > > morning to see if I can find the culprit.
> > > 
> > > xfs/566 on v6.11-rc1 would consistently cause the oops mentioned below.
> > > However, I was able to get xfs/566 to successfully execute for five times on a
> > > v6.11-rc1 kernel with the following commits reverted,
> > > 
> > > 83ab38ef0a0b2407d43af9575bb32333fdd74fb2
> > > 695ef796467ed228b60f1915995e390aea3d85c6
> > > 9bc2ff871f00437ad2f10c1eceff51aaa72b478f
> > > 
> > > Reinstating commit 83ab38ef0a0b2407d43af9575bb32333fdd74fb2 causes the kernel
> > > to oops once again.
> > 
> > Durr, does this help?
> 
> Yes, it does!  After ~8, a full fstests run completes without incident.
> 
> (vs. before where it would blow up within 2 minutes)
> 
> Thanks for the fix; you can add
> Tested-by: Darrick J. Wong <djwong@kernel.org>

Ofc as soon as this I push it to the whole fleet then things start
failing again. :(

> --D
> 
> > 
> > diff --git a/kernel/jump_label.c b/kernel/jump_label.c
> > index 4ad5ed8adf96..57f70dfa1f3d 100644
> > --- a/kernel/jump_label.c
> > +++ b/kernel/jump_label.c
> > @@ -236,7 +236,7 @@ void static_key_disable_cpuslocked(struct static_key *key)
> >  	}
> >  
> >  	jump_label_lock();
> > -	if (atomic_cmpxchg(&key->enabled, 1, 0))
> > +	if (atomic_cmpxchg(&key->enabled, 1, 0) == 1)
> >  		jump_label_update(key);
> >  	jump_label_unlock();
> >  }
> > 
>