linux-kernel - Re: [rfc/patch] mm/slub: restore/expand unfreeze

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Message-ID: <86ead66e34c5c3a59b0bf773ed40767b4282b768.camel@gmx.de>
Date:   Mon, 26 Jul 2021 12:04:23 +0200
From:   Mike Galbraith <efault@....de>
To:     Vlastimil Babka <vbabka@...e.cz>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     linux-rt-users@...r.kernel.org,
        Mel Gorman <mgorman@...hsingularity.net>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [rfc/patch] mm/slub: restore/expand unfreeze_partials() local
 exclusion scope

On Sun, 2021-07-25 at 21:34 +0200, Vlastimil Babka wrote:
> On 7/25/21 9:12 PM, Vlastimil Babka wrote:
> > +       /*
> > +        * On !RT we just want to disable preemption, on RT we need
> > the lock
> > +        * for real. This happens to match local_lock() semantics.
> > +        */
> > +       local_lock(&s->cpu_slab->lock);
>
> OK I realized (and tglx confirmed) that this will blow up on !RT +
> lockdep if interrupted by ___slab_alloc() that will do
> local_lock_irqsave(). So back to #ifdefs it is. But should work as-is
> for RT testing.

I called it off after 3 1/2 hours.  Bug blew box outta the water 10
times in about half of that, so methinks it's safe to call it dead.

	-Mike