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| author | Chris Metcalf <cmetcalf@tilera.com> | 2011-06-02 10:19:41 -0400 |
|---|---|---|
| committer | Pekka Enberg <penberg@kernel.org> | 2011-06-03 19:33:49 +0300 |
| commit | d4d84fef6d0366b585b7de13527a0faeca84d9ce (patch) | |
| tree | c67449976f955cff4a2fe8a74affc2dd67c37b7e | |
| parent | 55922c9d1b84b89cb946c777fddccb3247e7df2c (diff) | |
| download | blackbird-op-linux-d4d84fef6d0366b585b7de13527a0faeca84d9ce.tar.gz blackbird-op-linux-d4d84fef6d0366b585b7de13527a0faeca84d9ce.zip | |
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>
| -rw-r--r-- | include/linux/percpu.h | 3 | ||||
| -rw-r--r-- | mm/slub.c | 12 |
2 files changed, 7 insertions, 8 deletions
diff --git a/include/linux/percpu.h b/include/linux/percpu.h index 8b97308e65df..9ca008f0c542 100644 --- a/include/linux/percpu.h +++ b/include/linux/percpu.h @@ -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, ...) \ ({ \ diff --git a/mm/slub.c b/mm/slub.c index 7be0223531b0..35f351f26193 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -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; |
