From: Dan Carpenter <dan.carpenter@oracle.com>
To: Vladimir Davydov <vdavydov@parallels.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.cz>, Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH -mm] slab: update_memcg_params: explicitly check that old array != NULL
Date: Mon, 26 Jan 2015 18:13:59 +0300 [thread overview]
Message-ID: <20150126151359.GD6507@mwanda> (raw)
In-Reply-To: <20150126104534.GA28978@esperanza>
On Mon, Jan 26, 2015 at 01:45:34PM +0300, Vladimir Davydov wrote:
> On Mon, Jan 26, 2015 at 01:23:05PM +0300, Dan Carpenter wrote:
> > On Mon, Jan 26, 2015 at 01:01:19PM +0300, Vladimir Davydov wrote:
> > > This warning is false-positive, because @old equals NULL iff
> > > @memcg_nr_cache_ids equals 0.
> >
> > I don't see how it could be a false positive. The "old" pointer is
> > dereferenced inside the call to memset() so unless memset is a macro the
> > compiler isn't going to optimize the dereference away.
>
> old->entries is not dereferenced: memcg_cache_array->entries is not a
> pointer - it is embedded to the memcg_cache_array struct.
Ah. Ok. Thanks.
regards,
dan carpenter
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prev parent reply other threads:[~2015-01-26 15:14 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-26 8:56 [mmotm:master 200/417] mm/slab_common.c:166 update_memcg_params() warn: variable dereferenced before check 'old' (see line 162) Dan Carpenter
2015-01-26 10:01 ` [PATCH -mm] slab: update_memcg_params: explicitly check that old array != NULL Vladimir Davydov
2015-01-26 10:23 ` Dan Carpenter
2015-01-26 10:45 ` Vladimir Davydov
2015-01-26 15:13 ` Dan Carpenter [this message]
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