Messages in this thread | | | Date | Tue, 18 Feb 2014 22:34:00 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v4 1/3] qspinlock: Introducing a 4-byte queue spinlock implementation |
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On Tue, Feb 18, 2014 at 02:39:31PM -0500, Waiman Long wrote: > The #ifdef is harder to take away here. The point is that doing a 32-bit > exchange may accidentally steal the lock with the additional code to handle > that. Doing a 16-bit exchange, on the other hand, will never steal the lock > and so don't need the extra handling code. I could construct a function with > different return values to handle the different cases if you think it will > make the code easier to read.
Does it really pay to use xchg() with all those fixup cases? Why not have a single cmpxchg() loop that does just the exact atomic op you want?
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