Messages in this thread | | | Subject | Re: NFS deadlock explained (on S/390) | From | "Ulrich Weigand" <> | Date | Mon, 3 Sep 2001 14:35:43 +0200 |
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Manfred Spraul:
>I think in_irq() and in_interrupt() should check the cpu interrupt flag >and return TRUE if the per-cpu interrupts are disabled. > >The current behavious is just weird: > spin_lock_bh(); > in_interrupt(); --> true > spin_unlock_bh(); > spin_lock_irq(); > in_interrupt(); --> false > spin_unlock_irq();
I see. Instead of checking the interrupt flag in in_irq(), spin_lock_irq could also simply increment the local_irq_count, just like spin_lock_bh increments the local_bh_count.
>> Whether this same situation can explain the deadlocks seen on >> other platforms depends on whether the drivers used there exhibit >> similar locking behaviours as the QDIO driver, of course. > >It should be possible to detect that automatically: if >dev_kfree_skb_any() is called outside irq context with disabled per-cpu >interrupts then it's probably due to a spin_lock_irq() and could >deadlock.
This would definitely solve the deadlock in our case. However, I'm not sure this doesn't have some adverse effect on other code; e.g. there are quite a few routines that use if (!in_interrupt()) as a bug-check, and some might possibly be called from inside a spin_lock_irq ...
Mit freundlichen Gruessen / Best Regards
Ulrich Weigand
-- Dr. Ulrich Weigand Linux for S/390 Design & Development IBM Deutschland Entwicklung GmbH, Schoenaicher Str. 220, 71032 Boeblingen Phone: +49-7031/16-3727 --- Email: Ulrich.Weigand@de.ibm.com
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