Re: [PATCH -mm v2 5/8] slub: make slab_free non-preemptable

Christoph Lameter
2014-06-06T14:47:02Z

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@linux.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
}