From: Richard Henderson <rth@twiddle.net>
To: Stephen Hemminger <shemminger@osdl.org>
Cc: Linus Torvalds <torvalds@transmeta.com>,
Andrea Arcangeli <andrea@suse.de>, Andrew Morton <akpm@digeo.com>,
Andi Kleen <ak@suse.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] (1/4) 2.5.59 fast reader/writer lock for gettimeofday
Date: Tue, 28 Jan 2003 23:06:39 -0800 [thread overview]
Message-ID: <20030128230639.A17385@twiddle.net> (raw)
In-Reply-To: <1043797341.10150.300.camel@dell_ss3.pdx.osdl.net>; from shemminger@osdl.org on Tue, Jan 28, 2003 at 03:42:21PM -0800
On Tue, Jan 28, 2003 at 03:42:21PM -0800, Stephen Hemminger wrote:
> +static inline void fr_write_begin(frlock_t *rw)
> +{
> + preempt_disable();
> + rw->pre_sequence++;
> + wmb();
> +}
> +
> +static inline void fr_write_end(frlock_t *rw)
> +{
> + wmb();
> + rw->post_sequence++;
These need to be mb(), not wmb(), if you want the bits in between
to actually happen in between, as with your xtime example. At
present there's nothing stoping xtime from being *read* before
your read from pre_sequence happens.
r~
next prev parent reply other threads:[~2003-01-29 6:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-01-28 23:42 [PATCH] (1/4) 2.5.59 fast reader/writer lock for gettimeofday Stephen Hemminger
2003-01-29 7:06 ` Richard Henderson [this message]
2003-01-29 7:26 ` Anton Blanchard
2003-01-29 8:41 ` Andrew Morton
2003-01-30 1:15 ` frlock and barrier discussion Stephen Hemminger
2003-01-30 1:29 ` Andrea Arcangeli
2003-01-30 1:41 ` Richard Henderson
2003-01-30 1:52 ` Andrea Arcangeli
2003-01-31 0:41 ` Richard Henderson
2003-01-31 0:57 ` Andrea Arcangeli
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