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From: Robert Love <rml@tech9.net>
To: Joe Korty <joe.korty@ccur.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] 2.4 preemption bug in bh_kmap_irq
Date: 17 Jun 2003 17:24:26 -0700	[thread overview]
Message-ID: <1055895865.7069.1808.camel@localhost> (raw)
In-Reply-To: <20030414172730.GA17451@rudolph.ccur.com>

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.

	Robert Love



  parent reply	other threads:[~2003-06-18  0:10 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 [this message]
2003-06-19 12:16   ` Jens Axboe

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