From: Andrew Morton <akpm@linux-foundation.org>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>,
Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fix theoretical ccids_{read,write}_lock() race
Date: Sat, 21 Jul 2007 12:21:49 -0700 [thread overview]
Message-ID: <20070721122149.62c73ba5.akpm@linux-foundation.org> (raw)
In-Reply-To: <20070721191104.GA83@tv-sign.ru>
On Sat, 21 Jul 2007 23:11:04 +0400 Oleg Nesterov <oleg@tv-sign.ru> wrote:
> On 07/21, Andrew Morton wrote:
> >
> > On Sat, 21 Jul 2007 19:02:06 +0400 Oleg Nesterov <oleg@tv-sign.ru> wrote:
> >
> > > Make sure that spin_unlock_wait() is properly ordered wrt atomic_inc().
> > >
> > > Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
> > >
> > > --- t/net/dccp/ccid.c~ccid 2006-12-18 18:17:31.000000000 +0300
> > > +++ t/net/dccp/ccid.c 2007-07-21 18:29:21.000000000 +0400
> > > @@ -40,6 +40,7 @@ static inline void ccids_write_unlock(vo
> > > static inline void ccids_read_lock(void)
> > > {
> > > atomic_inc(&ccids_lockct);
> > > + smp_mb__after_atomic_inc();
> > > spin_unlock_wait(&ccids_lock);
> > > }
> > >
> >
> > Why not just use standard rwlocks in there?
> >
> > (This is probably an FAQ, but it should be).
>
> Perhaps because read_lock() doesn't allow to sleep?
>
down_read() does.
afaict the code doesn't sleep while holding that lock anwyay.
next prev parent reply other threads:[~2007-07-21 19:22 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-21 11:57 [PATCH] pi-futex: set PF_EXITING without taking ->pi_lock Oleg Nesterov
2007-07-21 12:31 ` Ingo Molnar
2007-07-21 14:18 ` Oleg Nesterov
2007-07-21 15:02 ` [PATCH] fix theoretical ccids_{read,write}_lock() race Oleg Nesterov
2007-07-21 19:02 ` Andrew Morton
2007-07-21 19:11 ` Oleg Nesterov
2007-07-21 19:21 ` Andrew Morton [this message]
2007-07-21 20:06 ` Oleg Nesterov
2007-07-21 15:05 ` [PATCH] pi-futex: set PF_EXITING without taking ->pi_lock Ingo Molnar
2007-07-21 16:39 ` Oleg Nesterov
2007-08-06 7:30 ` Ingo Molnar
2007-07-22 0:31 ` Paul Mackerras
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