From: Oleg Nesterov <oleg@redhat.com>
To: Ming Lei <tom.leiming@gmail.com>
Cc: Shaohua Li <shli@kernel.org>, Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: + atomic-improve-atomic_inc_unless_negative-atomic_dec_unless_positive .patch added to -mm tree
Date: Fri, 15 Mar 2013 14:46:32 +0100 [thread overview]
Message-ID: <20130315134632.GA18335@redhat.com> (raw)
In-Reply-To: <CACVXFVP+fGeWS3xwBfaQDFaH7=e_4CbgCru9DJczB2vyWuUL1g@mail.gmail.com>
On 03/15, Ming Lei wrote:
>
> On Fri, Mar 15, 2013 at 12:24 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> > static inline int atomic_inc_unless_negative(atomic_t *p)
> > {
> > int v, v1;
> > - for (v = 0; v >= 0; v = v1) {
> > + for (v = atomic_read(p); v >= 0; v = v1) {
> > v1 = atomic_cmpxchg(p, v, v + 1);
>
> Unfortunately, the above will exchange the current value even though
> it is negative, so it isn't correct.
Hmm, why? We always check "v >= 0" before we try to do
atomic_cmpxchg(old => v) ?
Oleg.
next prev parent reply other threads:[~2013-03-15 13:48 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-14 16:24 + atomic-improve-atomic_inc_unless_negative-atomic_dec_unless_positive .patch added to -mm tree Oleg Nesterov
2013-03-15 3:46 ` Ming Lei
2013-03-15 13:46 ` Oleg Nesterov [this message]
2013-03-15 15:13 ` Ming Lei
2013-03-15 16:51 ` Oleg Nesterov
2013-03-15 17:23 ` Frederic Weisbecker
2013-03-15 17:51 ` Oleg Nesterov
2013-03-15 18:34 ` Frederic Weisbecker
2013-03-15 20:17 ` Paul E. McKenney
2013-03-16 18:30 ` Oleg Nesterov
2013-03-17 17:26 ` Paul E. McKenney
2013-03-21 17:08 ` Oleg Nesterov
2013-03-21 17:34 ` Paul E. McKenney
2013-03-21 18:03 ` Eric Dumazet
2013-03-21 18:30 ` Oleg Nesterov
2013-03-21 22:56 ` Eric Dumazet
2013-03-22 12:59 ` Oleg Nesterov
2013-03-22 16:34 ` Paul E. McKenney
2013-03-16 18:19 ` Oleg Nesterov
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