From 9a543f007b702b0be4acacad416a0f90233b4558 Mon Sep 17 00:00:00 2001 From: Yunfeng Ye Date: Fri, 19 Nov 2021 16:43:25 -0800 Subject: 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 Reviewed-by: Vlastimil Babka Reviewed-by: John Hubbard Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slab.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'mm/slab.c') diff --git a/mm/slab.c b/mm/slab.c index da132a9ae6f8..ca4822f6b2b6 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -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); -- cgit