linux-kernel - [PATCH AUTOSEL 5.2 51/85] mm/slab_common.c: work around clang bug #42570

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Message-Id: <20190726133936.11177-51-sashal@kernel.org>
Date:   Fri, 26 Jul 2019 09:39:01 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Arnd Bergmann <arnd@...db.de>,
        David Rientjes <rientjes@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>, linux-mm@...ck.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH AUTOSEL 5.2 51/85] mm/slab_common.c: work around clang bug #42570

From: Arnd Bergmann <arnd@...db.de>

[ Upstream commit a07057dce2823e10d64a2b73cefbf09d8645efe9 ]

Clang gets rather confused about two variables in the same special
section when one of them is not initialized, leading to an assembler
warning later:

  /tmp/slab_common-18f869.s: Assembler messages:
  /tmp/slab_common-18f869.s:7526: Warning: ignoring changed section attributes for .data..ro_after_init

Adding an initialization to kmalloc_caches is rather silly here
but does avoid the issue.

Link: https://bugs.llvm.org/show_bug.cgi?id=42570
Link: http://lkml.kernel.org/r/20190712090455.266021-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Acked-by: David Rientjes <rientjes@...gle.com>
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>
Cc: Roman Gushchin <guro@...com>
Cc: Shakeel Butt <shakeelb@...gle.com>
Cc: Vladimir Davydov <vdavydov.dev@...il.com>
Cc: Andrey Konovalov <andreyknvl@...gle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 mm/slab_common.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 58251ba63e4a..cbd3411f644e 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1003,7 +1003,8 @@ struct kmem_cache *__init create_kmalloc_cache(const char *name,
 }
 
 struct kmem_cache *
-kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1] __ro_after_init;
+kmalloc_caches[NR_KMALLOC_TYPES][KMALLOC_SHIFT_HIGH + 1] __ro_after_init =
+{ /* initialization for https://bugs.llvm.org/show_bug.cgi?id=42570 */ };
 EXPORT_SYMBOL(kmalloc_caches);
 
 /*
-- 
2.20.1