From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: PATCH (for comment): ide-cd possible race in PIO mode
Date: Wed, 17 Nov 2004 16:25:30 +0000
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	 <20041117153706.GH26240@suse.de>
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To: Jens Axboe <axboe@suse.de>
Cc: linux-ide@vger.kernel.org, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

On Mer, 2004-11-17 at 15:37, Jens Axboe wrote:
> > -		HWIF(drive)->OUTB(WIN_PACKETCMD, IDE_COMMAND_REG);
> > +		spin_lock_irqsave(&ide_lock, flags);
> > +		HWIF(drive)->OUTBSYNC(WIN_PACKETCMD, IDE_COMMAND_REG);
> > +		ndelay(400);
> > +		spin_unlock_irqsave(&ide_lock, flags);
> >  		return (*handler) (drive);
> >  	}
> >  }
> 
> What good does the lock do?

The same as in ide_execute_command - make sure we don't take an IDE
interrupt that tries to read the state during the delay. That is the old
2.4 "may drives shared IRQ random fails" fix and why the lock is taken
in ide_execute_command.