The patch titled
Subject: slub: avoid false-postive warning
has been added to the -mm tree. Its filename is
slub-avoid-false-postive-warning.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/slub-avoid-false-postive-warning.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/slub-avoid-false-postive-warning.patch
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------------------------------------------------------
From: Arnd Bergmann <arnd@xxxxxxxx>
Subject: slub: avoid false-postive warning
The slub allocator gives us some incorrect warnings when
CONFIG_PROFILE_ANNOTATED_BRANCHES is set, as the unlikely() macro prevents
it from seeing that the return code matches what it was before:
mm/slub.c: In function `kmem_cache_free_bulk':
mm/slub.c:262:23: error: `df.s' may be used uninitialized in this function [-Werror=maybe-uninitialized]
mm/slub.c:2943:3: error: `df.cnt' may be used uninitialized in this function [-Werror=maybe-uninitialized]
mm/slub.c:2933:4470: error: `df.freelist' may be used uninitialized in this function [-Werror=maybe-uninitialized]
mm/slub.c:2943:3: error: `df.tail' may be used uninitialized in this function [-Werror=maybe-uninitialized]
I have not been able to come up with a perfect way for dealing with this,
the three options I see are:
- add a bogus initialization, which would increase the runtime overhead
- replace unlikely() with unlikely_notrace()
- remove the unlikely() annotation completely
I checked the object code for a typical x86 configuration and the last two
cases produce the same result, so I went for the last one, which is the
simplest.
Link: http://lkml.kernel.org/r/20161024155704.3114445-1-arnd@xxxxxxxx
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Acked-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Laura Abbott <labbott@xxxxxxxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN mm/slub.c~slub-avoid-false-postive-warning mm/slub.c
--- a/mm/slub.c~slub-avoid-false-postive-warning
+++ a/mm/slub.c
@@ -3076,7 +3076,7 @@ void kmem_cache_free_bulk(struct kmem_ca
struct detached_freelist df;
size = build_detached_freelist(s, size, p, &df);
- if (unlikely(!df.page))
+ if (!df.page)
continue;
slab_free(df.s, df.page, df.freelist, df.tail, df.cnt,_RET_IP_);
_
Patches currently in -mm which might be from arnd@xxxxxxxx are
slub-avoid-false-postive-warning.patch
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