Messages in this thread |  | | Date | Mon, 12 Nov 2001 18:34:42 +0100 | From | Jens Axboe <> | Subject | Re: sbp2.c on SMP |
| |
On Sun, Nov 11 2001, Andrew Morton wrote: > Guys, > > drivers/ieee1394/sbp2.c deadlocks immediately on SMP, because > io_request_lock is not held over its call to scsi_old_done(). > > I don't know why scsi_old_done() actually requires io_request_lock; > perhaps Jens could comment on whether I've taken the lock in the > appropriate place?
Yes it looks fine, unfortunately the mid layer locking design is crappy like that. Imposing locking downwards is just not good style :/
I've actually had quite good luck changing this for future kernels -- it was required to remove io_request_lock anyways.
> The games which scsi_old_done() plays with spinlocks and interrupt > enabling are really foul. If someone calls it with interrupts disabled > (sbp2 does this) then scsi_old_done() will enable interrupts for you. > If, for example, you call scsi_old_done() under spin_lock_irqsave(), > the reenabling of interrupts will expose you to deadlocks. Perhaps > scsi_old_done() should just use spin_unlock()/spin_lock()?
Yep it's not nice either. I wouldn't change that without further auditing though.
-- Jens Axboe
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |