linux-kernel - Re: [PATCH -mm v2 5/8] slub: make slab

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Date:	Fri, 6 Jun 2014 09:46:57 -0500 (CDT)
From:	Christoph Lameter <cl@...two.org>
To:	Vladimir Davydov <vdavydov@...allels.com>
cc:	akpm@...ux-foundation.org, iamjoonsoo.kim@....com,
	rientjes@...gle.com, penberg@...nel.org, hannes@...xchg.org,
	mhocko@...e.cz, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH -mm v2 5/8] slub: make slab_free non-preemptable

On Fri, 6 Jun 2014, Vladimir Davydov wrote:

> This patch makes SLUB's implementation of kmem_cache_free
> non-preemptable. As a result, synchronize_sched() will work as a barrier
> against kmem_cache_free's in flight, so that issuing it before cache
> destruction will protect us against the use-after-free.


Subject: slub: reenable preemption before the freeing of slabs from slab_free

I would prefer to call the page allocator with preemption enabled if possible.

Signed-off-by: Christoph Lameter <cl@...ux.com>

Index: linux/mm/slub.c
===================================================================
--- linux.orig/mm/slub.c	2014-05-29 11:45:32.065859887 -0500
+++ linux/mm/slub.c	2014-06-06 09:45:12.822480834 -0500
@@ -1998,6 +1998,7 @@
 	if (n)
 		spin_unlock(&n->list_lock);

+	preempt_enable();
 	while (discard_page) {
 		page = discard_page;
 		discard_page = discard_page->next;
@@ -2006,6 +2007,7 @@
 		discard_slab(s, page);
 		stat(s, FREE_SLAB);
 	}
+	preempt_disable();
 #endif
 }

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