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Subject[patch 46/61] lock validator: special locking: slab
From: Ingo Molnar <mingo@elte.hu>

teach special (recursive) locking code to the lock validator. Has no
effect on non-lockdep kernels.

fix initialize-locks-via-memcpy assumptions.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
mm/slab.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 48 insertions(+), 11 deletions(-)

Index: linux/mm/slab.c
===================================================================
--- linux.orig/mm/slab.c
+++ linux/mm/slab.c
@@ -1026,7 +1026,8 @@ static void drain_alien_cache(struct kme
}
}

-static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
+static inline int cache_free_alien(struct kmem_cache *cachep, void *objp,
+ int nesting)
{
struct slab *slabp = virt_to_slab(objp);
int nodeid = slabp->nodeid;
@@ -1044,7 +1045,7 @@ static inline int cache_free_alien(struc
STATS_INC_NODEFREES(cachep);
if (l3->alien && l3->alien[nodeid]) {
alien = l3->alien[nodeid];
- spin_lock(&alien->lock);
+ spin_lock_nested(&alien->lock, nesting);
if (unlikely(alien->avail == alien->limit)) {
STATS_INC_ACOVERFLOW(cachep);
__drain_alien_cache(cachep, alien, nodeid);
@@ -1073,7 +1074,8 @@ static inline void free_alien_cache(stru
{
}

-static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
+static inline int cache_free_alien(struct kmem_cache *cachep, void *objp,
+ int nesting)
{
return 0;
}
@@ -1278,6 +1280,11 @@ static void init_list(struct kmem_cache

local_irq_disable();
memcpy(ptr, list, sizeof(struct kmem_list3));
+ /*
+ * Do not assume that spinlocks can be initialized via memcpy:
+ */
+ spin_lock_init(&ptr->list_lock);
+
MAKE_ALL_LISTS(cachep, ptr, nodeid);
cachep->nodelists[nodeid] = ptr;
local_irq_enable();
@@ -1408,7 +1415,7 @@ void __init kmem_cache_init(void)
}
/* 4) Replace the bootstrap head arrays */
{
- void *ptr;
+ struct array_cache *ptr;

ptr = kmalloc(sizeof(struct arraycache_init), GFP_KERNEL);

@@ -1416,6 +1423,11 @@ void __init kmem_cache_init(void)
BUG_ON(cpu_cache_get(&cache_cache) != &initarray_cache.cache);
memcpy(ptr, cpu_cache_get(&cache_cache),
sizeof(struct arraycache_init));
+ /*
+ * Do not assume that spinlocks can be initialized via memcpy:
+ */
+ spin_lock_init(&ptr->lock);
+
cache_cache.array[smp_processor_id()] = ptr;
local_irq_enable();

@@ -1426,6 +1438,11 @@ void __init kmem_cache_init(void)
!= &initarray_generic.cache);
memcpy(ptr, cpu_cache_get(malloc_sizes[INDEX_AC].cs_cachep),
sizeof(struct arraycache_init));
+ /*
+ * Do not assume that spinlocks can be initialized via memcpy:
+ */
+ spin_lock_init(&ptr->lock);
+
malloc_sizes[INDEX_AC].cs_cachep->array[smp_processor_id()] =
ptr;
local_irq_enable();
@@ -1753,6 +1770,8 @@ static void slab_destroy_objs(struct kme
}
#endif

+static void __cache_free(struct kmem_cache *cachep, void *objp, int nesting);
+
/**
* slab_destroy - destroy and release all objects in a slab
* @cachep: cache pointer being destroyed
@@ -1776,8 +1795,17 @@ static void slab_destroy(struct kmem_cac
call_rcu(&slab_rcu->head, kmem_rcu_free);
} else {
kmem_freepages(cachep, addr);
- if (OFF_SLAB(cachep))
- kmem_cache_free(cachep->slabp_cache, slabp);
+ if (OFF_SLAB(cachep)) {
+ unsigned long flags;
+
+ /*
+ * lockdep: we may nest inside an already held
+ * ac->lock, so pass in a nesting flag:
+ */
+ local_irq_save(flags);
+ __cache_free(cachep->slabp_cache, slabp, 1);
+ local_irq_restore(flags);
+ }
}
}

@@ -3062,7 +3090,16 @@ static void free_block(struct kmem_cache
if (slabp->inuse == 0) {
if (l3->free_objects > l3->free_limit) {
l3->free_objects -= cachep->num;
+ /*
+ * It is safe to drop the lock. The slab is
+ * no longer linked to the cache. cachep
+ * cannot disappear - we are using it and
+ * all destruction of caches must be
+ * serialized properly by the user.
+ */
+ spin_unlock(&l3->list_lock);
slab_destroy(cachep, slabp);
+ spin_lock(&l3->list_lock);
} else {
list_add(&slabp->list, &l3->slabs_free);
}
@@ -3088,7 +3125,7 @@ static void cache_flusharray(struct kmem
#endif
check_irq_off();
l3 = cachep->nodelists[node];
- spin_lock(&l3->list_lock);
+ spin_lock_nested(&l3->list_lock, SINGLE_DEPTH_NESTING);
if (l3->shared) {
struct array_cache *shared_array = l3->shared;
int max = shared_array->limit - shared_array->avail;
@@ -3131,14 +3168,14 @@ free_done:
* Release an obj back to its cache. If the obj has a constructed state, it must
* be in this state _before_ it is released. Called with disabled ints.
*/
-static inline void __cache_free(struct kmem_cache *cachep, void *objp)
+static void __cache_free(struct kmem_cache *cachep, void *objp, int nesting)
{
struct array_cache *ac = cpu_cache_get(cachep);

check_irq_off();
objp = cache_free_debugcheck(cachep, objp, __builtin_return_address(0));

- if (cache_free_alien(cachep, objp))
+ if (cache_free_alien(cachep, objp, nesting))
return;

if (likely(ac->avail < ac->limit)) {
@@ -3393,7 +3430,7 @@ void kmem_cache_free(struct kmem_cache *
BUG_ON(virt_to_cache(objp) != cachep);

local_irq_save(flags);
- __cache_free(cachep, objp);
+ __cache_free(cachep, objp, 0);
local_irq_restore(flags);
}
EXPORT_SYMBOL(kmem_cache_free);
@@ -3418,7 +3455,7 @@ void kfree(const void *objp)
kfree_debugcheck(objp);
c = virt_to_cache(objp);
debug_check_no_locks_freed(objp, obj_size(c));
- __cache_free(c, (void *)objp);
+ __cache_free(c, (void *)objp, 0);
local_irq_restore(flags);
}
EXPORT_SYMBOL(kfree);
-
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