From: Jens Axboe <axboe@suse.de>
To: Robert Love <rml@tech9.net>
Cc: Joe Korty <joe.korty@ccur.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] 2.4 preemption bug in bh_kmap_irq
Date: Thu, 19 Jun 2003 14:16:58 +0200 [thread overview]
Message-ID: <20030619121658.GK6445@suse.de> (raw)
In-Reply-To: <1055895865.7069.1808.camel@localhost>
On Tue, Jun 17 2003, Robert Love wrote:
> On Mon, 2003-04-14 at 10:27, Joe Korty wrote:
>
> > The bug is that bh_map_irq *conditionally* calls kmap_atomic (which
> > disables preemption as one of its functions), while bh_unmap_irq
> > *unconditionally* calls kunmap_atomic (which enables it). This
> > imbalance results in a occasional off-by-one preempt_count, which in
> > turn causes IDE PIO mode interrupt code (specifically, read_intr) to
> > erronously invoke preempt_schedule while at interrupt level.
>
> Thanks for this (and sorry for the very delayed reply).
>
> I am going to put this in the 2.4.21 preempt-kernel patch, because
> actually someone else here at MontaVista fixed the problem in the same
> exact way a loooong time ago and it seems to work.
>
> I agree it is suboptimal and I will be happy to take patches from
> someone else with a better idea. Until then, simplicity rules. Thanks.
See 2.5 for the right fix.
--
Jens Axboe
prev parent reply other threads:[~2003-06-19 12:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-14 17:27 [PATCH] 2.4 preemption bug in bh_kmap_irq Joe Korty
2003-04-14 17:40 ` Marc-Christian Petersen
2003-04-14 19:57 ` Joe Korty
2003-06-18 0:24 ` Robert Love
2003-06-19 12:16 ` Jens Axboe [this message]
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