Messages in this thread |  | | | Date | Mon, 25 Mar 2002 13:33:02 -0500 (EST) | | From | Paul Clements <> | | Subject | Re: [PATCH] 2.4.18 raid1 - fix SMP locking/interrupt errors, fix resync counter errors |
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On Sun, 24 Mar 2002, Andrew Morton wrote:
> 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.
Yes, that was precisely what was happening in raid1. There were "nested" spin_lock_irq() calls.
> 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.
I was wondering about the performance of these. I was reluctant to change all occurrences of spin_lock_irq() to the save/restore versions, even though that seemed like the safest thing to do, so I had to analyze every code path where spin_locks were involved to see which ones absolutely needed to change...very tedious.
Thanks for the explanations.
-- Paul
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