From: Andrew Morton <akpm@linux-foundation.org>
To: Joe Perches <joe@perches.com>
Cc: Yann Collet <cyan@fb.com>, Vasily Averin <vvs@virtuozzo.com>,
Gao Xiang <hsiangkao@aol.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Gao Xiang <xiang@kernel.org>
Subject: Re: [PATCH] lib/lz4: smatch warning in LZ4_decompress_generic()
Date: Sun, 7 Jun 2020 18:24:28 -0700 [thread overview]
Message-ID: <20200607182428.0d9ce5139b9ab4f36eefca1b@linux-foundation.org> (raw)
In-Reply-To: <3bf931c6ea0cae3e23f3485801986859851b4f04.camel@perches.com>
On Sun, 07 Jun 2020 18:02:44 -0700 Joe Perches <joe@perches.com> wrote:
> On Mon, 2020-06-08 at 00:40 +0000, Yann Collet wrote:
> > Hi Vasily
> >
> >
> > If I do understand the discussion, the question is about usage of `&` instead of `&&`,
> > and the speculation that it might be an error.
> >
> > It's not an error. Unfortunately, explaining the reasoning behind this decision is a bit long.
>
> Likely better to add a comment around the use so that
> another patch like this doesn't get submitted again.
>
> Perhaps something like:
Yup.
From: Joe Perches <joe@perches.com>
Subject: lib/lz4/lz4_decompress.c: document deliberate use of `&'
This operation was intentional, but tools such as smatch will warn that it
might not have been.
Link: http://lkml.kernel.org/r/3bf931c6ea0cae3e23f3485801986859851b4f04.camel@perches.com
Cc: Yann Collet <cyan@fb.com>
Cc: Vasily Averin <vvs@virtuozzo.com>
Cc: Gao Xiang <hsiangkao@aol.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
lib/lz4/lz4_decompress.c | 3 +++
1 file changed, 3 insertions(+)
--- a/lib/lz4/lz4_decompress.c~lib-lz4-smatch-warning-in-lz4_decompress_generic
+++ a/lib/lz4/lz4_decompress.c
@@ -141,6 +141,9 @@ static FORCE_INLINE int LZ4_decompress_g
* space in the output for those 18 bytes earlier, upon
* entering the shortcut (in other words, there is a
* combined check for both stages).
+ *
+ * The & in the likely() below is intentionally not && so that
+ * some compilers can produce better parallelized runtime code
*/
if ((endOnInput ? length != RUN_MASK : length <= 8)
/*
_
prev parent reply other threads:[~2020-06-08 1:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200606143646.GB10839.ref@hsiangkao-HP-ZHAN-66-Pro-G1>
2020-06-06 13:28 ` [PATCH] lib/lz4: smatch warning in LZ4_decompress_generic() Vasily Averin
2020-06-06 14:36 ` Gao Xiang
2020-06-06 15:16 ` Vasily Averin
2020-06-08 0:40 ` Yann Collet
2020-06-08 1:02 ` Joe Perches
2020-06-08 1:24 ` Andrew Morton [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200607182428.0d9ce5139b9ab4f36eefca1b@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=cyan@fb.com \
--cc=hsiangkao@aol.com \
--cc=joe@perches.com \
--cc=linux-kernel@vger.kernel.org \
--cc=vvs@virtuozzo.com \
--cc=xiang@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).