linux-kernel - Re: [PATCH v3] mm/slab.c: add node spinlock protect in __cache_free

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Date:   Thu, 30 Jul 2020 16:45:02 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     qiang.zhang@...driver.com
cc:     cl@...ux.com, penberg@...nel.org, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mm/slab.c: add node spinlock protect in
 __cache_free_alien

On Thu, 30 Jul 2020, qiang.zhang@...driver.com wrote:

> From: Zhang Qiang <qiang.zhang@...driver.com>
> 
> for example:
> 			        node0
> 	cpu0				                cpu1
> slab_dead_cpu
>    >mutex_lock(&slab_mutex)
>      >cpuup_canceled                            slab_dead_cpu
>        >mask = cpumask_of_node(node)               >mutex_lock(&slab_mutex)
>        >n = get_node(cachep0, node0)
>        >spin_lock_irq(n&->list_lock)
>        >if (!cpumask_empty(mask)) == true
>        	>spin_unlock_irq(&n->list_lock)
> 	>goto free_slab
>        ....
>    >mutex_unlock(&slab_mutex)
> 
> ....						   >cpuup_canceled
> 						     >mask = cpumask_of_node(node)
> kmem_cache_free(cachep0 )			     >n = get_node(cachep0, node0)
>  >__cache_free_alien(cachep0 )			     >spin_lock_irq(n&->list_lock)
>    >n = get_node(cachep0, node0)		     >if (!cpumask_empty(mask)) == false
>    >if (n->alien && n->alien[page_node])	     >alien = n->alien
>      >alien = n->alien[page_node]	             >n->alien = NULL
>      >....					     >spin_unlock_irq(&n->list_lock)
> 						     >....
> 

As mentioned in the review of v1 of this patch, we likely want to do a fix 
for cpuup_canceled() instead.