BUG: [2.4.18+] IDE Race Condition

[Ross Biro]

There is at least one more IDE race condition in 2.4.18 and 2.4.21-pre3. 
 Basically the interrupt for the controller being serviced is left on 
while setting up the next command.  I'm not sure how much trouble it can 
cause but it does lead to some interesting stack traces.

The condition
if (masked_irq && hwif->irq != masked_irq)
in ide_do_request should be replaced with
if (!masked_irq || hwif->irq != masked_irq)
in two places.

This doesn't totally eliminate the race conditions, but it does minimize 
them some more.  I can still see a race in 2.4.18.  I'll say more about 
it once I've tracked it down.

    Ross