From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Shtylyov Subject: Re: [PATCH] Correctly prevent IDE timer expiry function to run if request was already handled Date: Fri, 06 Apr 2007 23:22:02 +0400 Message-ID: <46169DDA.6020008@ru.mvista.com> References: <20070406173603.GA82722@freefall.freebsd.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20070406173603.GA82722@freefall.freebsd.org> Sender: linux-kernel-owner@vger.kernel.org To: Suleiman Souhlal Cc: bzolnier@gmail.com, linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-ide@vger.kernel.org Hello. Suleiman Souhlal wrote: > It is possible for the timer expiry function to run even though the > request has already been handled: ide_timer_expiry() only checks that > the handler is not NULL, but it is possible that we have handled a > request (thus clearing the handler) and then started a new request > (thus starting the timer again, and setting a handler). > A simple way to exhibit this is to set the DMA timeout to 1 jiffy and > run dd: The kernel will panic after a few minutes because > ide_timer_expiry() tries to add a timer when it's already active. > To fix this, we simply add a request generation count that gets > incremented at every interrupt, and check in ide_timer_expiry() that > we have not already handled a new interrupt before running the expiry > function. Couldn't this be addressed by simply changing add_timer() to mod_timer()? MBR, Sergei