From: James Bottomley <James.Bottomley@steeleye.com>
To: Jesse Barnes <jbarnes@engr.sgi.com>
Cc: linux-arch@vger.kernel.org, jeremy@sgi.com
Subject: Re: [PATCH] I/O space write barrier
Date: 23 Sep 2004 15:27:24 -0400 [thread overview]
Message-ID: <1095967651.2157.42.camel@mulgrave> (raw)
In-Reply-To: <200409231507.26672.jbarnes@engr.sgi.com>
On Thu, 2004-09-23 at 15:07, Jesse Barnes wrote:
> If we're waiting for an interrupt here, I don't think it matters if we flush
> or order, we'll wait the same amount of time regardless.
I don't think so. Your ordering barrier doesn't cause a posted write
flush. Posted writes have theoretically no upper limit defined in the
spec for the time they may remain posted, so in the former case, you are
guaranteed that by the time you set the flag and exit the function that
interrupts are enabled in the qla1280. If you apply the patch you sent
in, this guarantee is broken and you don't really know how much longer
after exiting the function it will be before interrupts become enabled
(although in practice it's probably only of the order of ms).
James
next prev parent reply other threads:[~2004-09-23 19:27 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-23 18:48 [PATCH] I/O space write barrier Jesse Barnes
2004-09-23 19:03 ` James Bottomley
2004-09-23 19:07 ` Jesse Barnes
2004-09-23 19:27 ` James Bottomley [this message]
2004-09-23 19:41 ` Jesse Barnes
2004-09-23 19:57 ` Jeremy Higdon
2004-09-23 22:22 ` Jeremy Higdon
2004-09-23 23:36 ` James Bottomley
2004-09-24 5:03 ` Jeremy Higdon
2004-09-23 19:55 ` Jeremy Higdon
2004-09-23 20:09 ` Jesse Barnes
2004-09-27 0:45 ` Benjamin Herrenschmidt
2004-09-27 15:41 ` Jesse Barnes
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