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SubjectRe: sbp2.c on SMP
On Sun, Nov 11, 2001 at 05:37:21PM -0800, Andrew Morton wrote:
>
> With the appended patch I can confirm that the driver happily runs
> `dbench 40' for half an hour on dual x86. Even when you kick the

Thanks a lot.

> disk onto the floor (sorry, HJ).

That is a good stress test.

>
> 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()?
>
> I tried enabling SBP2_USE_REAL_SPINLOCKS in sbp2.c and that appears to
> work just fine, although I haven't left that change in place here.
>
> You don't actually _need_ SMP hardware to test SMP code, BTW. You
> can just build an SMP kernel and run that on a uniprocessor box.
> This will still catch a wide range of bugs - it certainly detects
> the lockup which was occurring because of the scsi_old_done() thing.
>
> Incidentally, it would be nice to be able to get this driver working
> properly when linked into the kernel - it makes debugging much easier :)
>

I guess I can try that. The only main issue will be the order of
initialization.



H.J.
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