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mm: emit the "free" trace report before freeing memory in kmem_cache_free() 

After the memory is freed, it can be immediately allocated by other
CPUs, before the "free" trace report has been emitted.  This causes
inaccurate traces.

For example, if the following sequence of events occurs:

    CPU 0                 CPU 1

  (1) alloc xxxxxx
  (2) free  xxxxxx
                         (3) alloc xxxxxx
                         (4) free  xxxxxx

Then they will be inaccurately reported via tracing, so that they appear
to have happened in this order:

    CPU 0                 CPU 1

  (1) alloc xxxxxx
                         (2) alloc xxxxxx
  (3) free  xxxxxx
                         (4) free  xxxxxx

This makes it look like CPU 1 somehow managed to allocate memory that
CPU 0 still had allocated for itself.

In order to avoid this, emit the "free xxxxxx" tracing report just
before the actual call to free the memory, instead of just after it.

Link: https://lkml.kernel.org/r/374eb75d-7404-8721-4e1e-65b0e5b17279@huawei.com
Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Yunfeng Ye 2021-11-19 16:43:25 -08:00 committed by Linus Torvalds
parent 85b6d24646
commit 9a543f007b
3 changed files with 3 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
mm/slab.c
View File

@ -3733,14 +3733,13 @@ void kmem_cache_free(struct kmem_cache *cachep, void *objp)
if (!cachep)
return;
trace_kmem_cache_free(_RET_IP_, objp, cachep->name);
local_irq_save(flags);
debug_check_no_locks_freed(objp, cachep->object_size);
if (!(cachep->flags & SLAB_DEBUG_OBJECTS))
debug_check_no_obj_freed(objp, cachep->object_size);
__cache_free(cachep, objp, _RET_IP_);
local_irq_restore(flags);
trace_kmem_cache_free(_RET_IP_, objp, cachep->name);
}
EXPORT_SYMBOL(kmem_cache_free);

3
mm/slob.c
View File

@ -666,6 +666,7 @@ static void kmem_rcu_free(struct rcu_head *head)
void kmem_cache_free(struct kmem_cache *c, void *b)
{
kmemleak_free_recursive(b, c->flags);
trace_kmem_cache_free(_RET_IP_, b, c->name);
if (unlikely(c->flags & SLAB_TYPESAFE_BY_RCU)) {
struct slob_rcu *slob_rcu;
slob_rcu = b + (c->size - sizeof(struct slob_rcu));
@ -674,8 +675,6 @@ void kmem_cache_free(struct kmem_cache *c, void *b)
} else {
__kmem_cache_free(b, c->size);
}
trace_kmem_cache_free(_RET_IP_, b, c->name);
}
EXPORT_SYMBOL(kmem_cache_free);

2
mm/slub.c
View File

@ -3526,8 +3526,8 @@ void kmem_cache_free(struct kmem_cache *s, void *x)
s = cache_from_obj(s, x);
if (!s)
return;
slab_free(s, virt_to_head_page(x), x, NULL, 1, _RET_IP_);
trace_kmem_cache_free(_RET_IP_, x, s->name);
slab_free(s, virt_to_head_page(x), x, NULL, 1, _RET_IP_);
}
EXPORT_SYMBOL(kmem_cache_free);