tree c30fc173d8b97343f8ae7b1b1ed511366af256ab
parent 90f30eccf41302a2542f5d374af243061902bd98
author Suleiman Souhlal <suleiman@google.com> 1176237517 +0200
committer Bartlomiej Zolnierkiewicz <bzolnier@gmail.com> 1176237517 +0200

ide: correctly prevent IDE timer expiry function to run if request was already handled

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.

Signed-off-by: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>