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| author | Vlastimil Babka <vbabka@suse.cz> | 2022-08-23 20:03:58 +0300 |
|---|---|---|
| committer | Vlastimil Babka <vbabka@suse.cz> | 2022-09-17 01:18:29 +0300 |
| commit | 41bec7c33f37aaae6e3737615e2dfa17a30ea985 (patch) | |
| tree | 1aa9c97766350abbf863da91f433d2bc6b0a39ee /mm/slub.c | |
| parent | c7323a5ad0786371f61dca49fc26f7ab3a68e0da (diff) | |
| download | linux-41bec7c33f37aaae6e3737615e2dfa17a30ea985.tar.xz | |
mm/slub: remove slab_lock() usage for debug operations
All alloc and free operations on debug caches are now serialized by
n->list_lock, so we can remove slab_lock() usage in validate_slab()
and list_slab_objects() as those also happen under n->list_lock.
Note the usage in list_slab_objects() could happen even on non-debug
caches, but only during cache shutdown time, so there should not be any
parallel freeing activity anymore. Except for buggy slab users, but in
that case the slab_lock() would not help against the common cmpxchg
based fast paths (in non-debug caches) anyway.
Also adjust documentation comments accordingly.
Suggested-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Diffstat (limited to 'mm/slub.c')
| -rw-r--r-- | mm/slub.c | 19 |
1 files changed, 8 insertions, 11 deletions
diff --git a/mm/slub.c b/mm/slub.c index a18a81a52307..37234e60591c 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -50,7 +50,7 @@ * 1. slab_mutex (Global Mutex) * 2. node->list_lock (Spinlock) * 3. kmem_cache->cpu_slab->lock (Local lock) - * 4. slab_lock(slab) (Only on some arches or for debugging) + * 4. slab_lock(slab) (Only on some arches) * 5. object_map_lock (Only for debugging) * * slab_mutex @@ -64,8 +64,9 @@ * The slab_lock is a wrapper around the page lock, thus it is a bit * spinlock. * - * The slab_lock is only used for debugging and on arches that do not - * have the ability to do a cmpxchg_double. It only protects: + * The slab_lock is only used on arches that do not have the ability + * to do a cmpxchg_double. It only protects: + * * A. slab->freelist -> List of free objects in a slab * B. slab->inuse -> Number of objects in use * C. slab->objects -> Number of objects in slab @@ -94,6 +95,9 @@ * allocating a long series of objects that fill up slabs does not require * the list lock. * + * For debug caches, all allocations are forced to go through a list_lock + * protected region to serialize against concurrent validation. + * * cpu_slab->lock local lock * * This locks protect slowpath manipulation of all kmem_cache_cpu fields @@ -4369,7 +4373,6 @@ static void list_slab_objects(struct kmem_cache *s, struct slab *slab, void *p; slab_err(s, slab, text, s->name); - slab_lock(slab, &flags); map = get_map(s, slab); for_each_object(p, s, addr, slab->objects) { @@ -4380,7 +4383,6 @@ static void list_slab_objects(struct kmem_cache *s, struct slab *slab, } } put_map(map); - slab_unlock(slab, &flags); #endif } @@ -5108,12 +5110,9 @@ static void validate_slab(struct kmem_cache *s, struct slab *slab, { void *p; void *addr = slab_address(slab); - unsigned long flags; - - slab_lock(slab, &flags); if (!check_slab(s, slab) || !on_freelist(s, slab, NULL)) - goto unlock; + return; /* Now we know that a valid freelist exists */ __fill_map(obj_map, s, slab); @@ -5124,8 +5123,6 @@ static void validate_slab(struct kmem_cache *s, struct slab *slab, if (!check_object(s, slab, p, val)) break; } -unlock: - slab_unlock(slab, &flags); } static int validate_slab_node(struct kmem_cache *s, |