Messages in this thread |  | | | From | "Manfred Spraul" <> | | Subject | Re: [PATCH] 2.4.18 raid1 - fix SMP locking/interrupt | | Date | Mon, 25 Mar 2002 20:50:26 +0100 |
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> > However a bare spin_unlock_irq() in a function means that > callers which wish to keep interrupts disabled are subtly > subverted. We've had bugs from this before. > It is trivial to catch such bugs at runtime. I tried it a year ago, and immediately run into sleep_on() users that legitimately call spin_lock_irq() with disabled interrupts. Perhaps they are gone now, I'll retest my patch.
> So the irqrestore functions are much more robust. I believe > that they should be the default choice. The non-restore > versions should be viewed as a micro-optimised version, > to be used with caution. The additional expense of the save/restore > is quite tiny - 20-30 cycles, perhaps.
OTHO, if a function doesn't work correctly if it's called with disabled interrupts, then it should not use spin_lock_irqsave() - it's misleading. e.g. if it calls kmalloc(GFP_KERNEL), down(), schedule(), etc.
-- Manfred
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