SLUB: Write to per cpu data when allocating it

It turns out that the cmpxchg16b emulation has to access vmalloced
percpu memory with interrupts disabled. If the memory has never
been touched before then the fault necessary to establish the
mapping will not to occur and the kernel will fail on boot.

Fix that by reusing the CONFIG_PREEMPT code that writes the
cpu number into a field on every cpu. Writing to the per cpu
area before causes the mapping to be established before we get
to a cmpxchg16b emulation.

Tested-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --git a/mm/slub.c b/mm/slub.c
index a6a783594ad44e4caf2ba7daafa16df15585fa48..f881874843a5ff67a3d1cef595c35bf72a3c3565 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1604,7 +1604,7 @@ static inline void note_cmpxchg_failure(const char *n,
 
 void init_kmem_cache_cpus(struct kmem_cache *s)
 {
-#if defined(CONFIG_CMPXCHG_LOCAL) && defined(CONFIG_PREEMPT)
+#ifdef CONFIG_CMPXCHG_LOCAL
        int cpu;
 
        for_each_possible_cpu(cpu)