Re: PATCH (for comment): ide-cd possible race in PIO mode

[Jens Axboe <axboe@suse.de>]

On Wed, Nov 17 2004, Alan Cox wrote:
> 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.

Ah I see, makes sense. I didn't think about the shared irq case.

-- 
Jens Axboe