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Message-ID: <fba5b2ca7472ea06690e4a92ba0fbd4dd8557f86.camel@gmx.de>
Subject: Re: [patch] v2 mm/slub: restore/expand unfreeze_partials() local
 exclusion scope
From:   Mike Galbraith <efault@gmx.de>
To:     Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     linux-rt-users@vger.kernel.org,
        Mel Gorman <mgorman@techsingularity.net>,
        Vlastimil Babka <vbabka@suse.cz>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date:   Sun, 18 Jul 2021 17:43:05 +0200
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It's moot, but for the record...

@@ -2418,6 +2418,17 @@ static void __unfreeze_partials(struct k
>  	if (n)
>  		spin_unlock_irqrestore(&n->list_lock, flags);
>
> +	/*
> +	 * If we got here via __slab_free() -> put_cpu_partial(),
> +	 * memcg_free_page_obj_cgroups() ->kfree() may send us
> +	 * back to __slab_free() -> put_cpu_partial() for an
> +	 * unfortunate second encounter with cpu_slab->lock.
> +	 */
> +	if (IS_ENABLED(CONFIG_PREEMPT_RT) && memcg_kmem_enabled()) {
> +		lockdep_assert_held(this_cpu_ptr(&s->cpu_slab.lock.lock));

...that assert needs to hide behind something less transparent.

	-Mike