From: Arnd Bergmann <arnd@arndb.de>
To: Kulikov Vasiliy <segooon@gmail.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: kernel-janitors@vger.kernel.org, Neil Brown <neilb@suse.de>,
Jens Axboe <jaxboe@fusionio.com>,
linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] md: do not use ++ in rcu_dereference() argument
Date: Mon, 6 Sep 2010 22:10:55 +0200 [thread overview]
Message-ID: <201009062210.56824.arnd@arndb.de> (raw)
In-Reply-To: <1283711539-7123-1-git-send-email-segooon@gmail.com>
On Sunday 05 September 2010 20:32:18 Kulikov Vasiliy wrote:
> From: Vasiliy Kulikov <segooon@gmail.com>
>
> rcu_dereference() is macro, so it might use its argument twice.
> Argument must not has side effects.
>
> It was found by compiler warning:
> drivers/md/raid1.c: In function ‘read_balance’:
> drivers/md/raid1.c:445: warning: operation on ‘new_disk’ may be undefined
I think the rcu_dereference macro should really not evaluate its argument
twice, and I don't see where it does.
As a general rule, we try to write macros in Linux such that they behave
like functions and don't have surprising side-effects.
Which kernel and gcc version do you see the warning with?
Arnd
next prev parent reply other threads:[~2010-09-06 20:11 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-05 18:32 [PATCH] md: do not use ++ in rcu_dereference() argument Kulikov Vasiliy
2010-09-05 19:01 ` Sam Ravnborg
2010-09-05 19:23 ` Kulikov Vasiliy
2010-09-05 20:39 ` Sam Ravnborg
2010-09-06 5:29 ` Neil Brown
2010-09-06 7:43 ` walter harms
2010-09-06 11:05 ` Neil Brown
2010-09-06 19:21 ` Sam Ravnborg
2010-09-08 7:04 ` Neil Brown
2010-09-16 12:54 ` Avi Kivity
2010-09-17 3:18 ` Neil Brown
2010-09-06 20:10 ` Arnd Bergmann [this message]
2010-09-07 19:21 ` Kulikov Vasiliy
2010-09-07 20:00 ` Arnd Bergmann
2010-09-07 20:50 ` Paul E. McKenney
2010-09-09 15:14 ` Arnd Bergmann
2010-09-10 3:46 ` Paul E. McKenney
2010-09-14 0:33 ` Paul E. McKenney
2010-09-15 12:28 ` Arnd Bergmann
2010-09-16 6:15 ` Paul E. McKenney
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