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slub: always align cpu_slab to honor cmpxchg_double requirement 

On an architecture without CMPXCHG_LOCAL but with DEBUG_VM enabled,
the VM_BUG_ON() in __pcpu_double_call_return_bool() will cause an early
panic during boot unless we always align cpu_slab properly.

In principle we could remove the alignment-testing VM_BUG_ON() for
architectures that don't have CMPXCHG_LOCAL, but leaving it in means
that new code will tend not to break x86 even if it is introduced
on another platform, and it's low cost to require alignment.

Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>
hifive-unleashed-5.1
Chris Metcalf 2011-06-02 10:19:41 -04:00 committed by Pekka Enberg
parent 55922c9d1b
commit d4d84fef6d
2 changed files with 7 additions and 8 deletions
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3
include/linux/percpu.h
View File

@ -259,6 +259,9 @@ extern void __bad_size_call_parameter(void);
* Special handling for cmpxchg_double. cmpxchg_double is passed two
* percpu variables. The first has to be aligned to a double word
* boundary and the second has to follow directly thereafter.
* We enforce this on all architectures even if they don't support
* a double cmpxchg instruction, since it's a cheap requirement, and it
* avoids breaking the requirement for architectures with the instruction.
*/
#define __pcpu_double_call_return_bool(stem, pcp1, pcp2, ...) \
({ \

12
mm/slub.c
View File

@ -2320,16 +2320,12 @@ static inline int alloc_kmem_cache_cpus(struct kmem_cache *s)
BUILD_BUG_ON(PERCPU_DYNAMIC_EARLY_SIZE <
SLUB_PAGE_SHIFT * sizeof(struct kmem_cache_cpu));
#ifdef CONFIG_CMPXCHG_LOCAL
/*
* Must align to double word boundary for the double cmpxchg instructions
* to work.
* Must align to double word boundary for the double cmpxchg
* instructions to work; see __pcpu_double_call_return_bool().
*/
s->cpu_slab = __alloc_percpu(sizeof(struct kmem_cache_cpu), 2 * sizeof(void *));
#else
/* Regular alignment is sufficient */
s->cpu_slab = alloc_percpu(struct kmem_cache_cpu);
#endif
s->cpu_slab = __alloc_percpu(sizeof(struct kmem_cache_cpu),
2 * sizeof(void *));
if (!s->cpu_slab)
return 0;