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Message-ID: <Pine.LNX.4.64.0704251613280.19217@blonde.wat.veritas.com>
Date: Wed, 25 Apr 2007 16:21:00 +0100 (BST)
From: Hugh Dickins <hugh@...itas.com>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Christoph Lameter <clameter@....com>, linux-kernel@...r.kernel.org
Subject: [PATCH -mm] slub: update cpu after new_slab()
SLUB gave me a NULL pointer dereference in slab_alloc(), in the
slab_lock(page) of its "Current cpuslab is acceptable" block: cpu
1 had been looking at cpu_slab[2], which then went NULL beneath it.
Since new_slab() may reenable interrupts and sleep (when __GFP_WAIT),
we may get rescheduled on a different cpu: so need to reevaluate it.
Signed-off-by: Hugh Dickins <hugh@...itas.com>
--- 2.6.21-rc7-mm1/mm/slub.c 2007-04-24 20:26:48.000000000 +0100
+++ linux/mm/slub.c 2007-04-25 15:49:12.000000000 +0100
@@ -1234,11 +1234,12 @@ have_slab:
page = new_slab(s, gfpflags, node);
if (page) {
+ cpu = smp_processor_id();
if (s->cpu_slab[cpu]) {
/*
- * Someone else populated the cpu_slab while
- * we enabled interrupts. The page may not
- * be on the requested node.
+ * Someone else populated the cpu_slab while we enabled
+ * interrupts, or we have got scheduled on another cpu.
+ * The page may not be on the requested node.
*/
if (node == -1 ||
page_to_nid(s->cpu_slab[cpu]) == node) {
-
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