From: Eric Dumazet <eric.dumazet@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andi Kleen <andi@firstfloor.org>,
Ben Hutchings <bhutchings@solarflare.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: >Re: [RFC] should VM_BUG_ON(cond) really evaluate cond
Date: Sun, 30 Oct 2011 18:59:53 +0100 [thread overview]
Message-ID: <1319997593.13597.76.camel@edumazet-laptop> (raw)
In-Reply-To: <CA+55aFz-mp8k7qdF3LaOjgX19TbzrCirGuCmGwqVMq9SwQ8yvw@mail.gmail.com>
Le dimanche 30 octobre 2011 à 10:48 -0700, Linus Torvalds a écrit :
> On Sun, Oct 30, 2011 at 10:41 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> >
> > Changing atomic_read(const atomic_t *v) prototype to
> > atomic_read(atomic_t *v) is not an option.
>
> Why not?
>
> #define atomic_read(v) ACCESS_AT_MOST_ONCE((v)->counter)
>
> seems to be the cleanest thing.
>
As I said, because v can be a const pointer provided by the caller.
Try it yourself and you'll discover hundred of call sites doing
.... some_function(const struct *xxx, ...)
{
if (atomic_read(&xxx->refcnt) <= 0)
do_something();
else
do_otherthing();
}
> And if you don't think this is "an option", I really can't see why you
> care about the extra instructions in the code stream either.
>
Not an option if we have to change all callers that expected to be able
to use a const atomic_t pointer.
OK, I now have to leave the net.
next prev parent reply other threads:[~2011-10-30 17:59 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-28 1:19 [RFC] should VM_BUG_ON(cond) really evaluate cond Eric Dumazet
2011-10-28 1:25 ` Andi Kleen
2011-10-28 1:34 ` Linus Torvalds
2011-10-28 1:44 ` Ben Hutchings
2011-10-28 2:52 ` Eric Dumazet
2011-10-28 3:29 ` Ben Hutchings
2011-10-28 4:43 ` >Re: " Eric Dumazet
2011-10-28 11:37 ` Linus Torvalds
2011-10-28 12:09 ` Eric Dumazet
2011-10-28 12:19 ` Linus Torvalds
2011-10-28 12:40 ` Linus Torvalds
2011-10-28 14:47 ` Eric Dumazet
2011-10-28 14:55 ` Linus Torvalds
2011-10-29 15:43 ` Eric Dumazet
2011-10-29 17:34 ` Linus Torvalds
2011-10-30 8:52 ` Eric Dumazet
2011-10-30 9:59 ` Andi Kleen
2011-10-30 15:16 ` Eric Dumazet
2011-10-30 17:07 ` Linus Torvalds
2011-10-30 17:41 ` Eric Dumazet
2011-10-30 17:48 ` Linus Torvalds
2011-10-30 17:59 ` Eric Dumazet [this message]
2011-10-30 18:09 ` Linus Torvalds
2011-11-02 0:14 ` Eric Dumazet
2011-11-01 4:06 ` Stephen Rothwell
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