On Mon, 2018-04-09 at 11:37 +0200, Christoph Hellwig wrote:
> This looks sensible, but I'm worried about taking a whole spinlock
> for every request completion, including irq disabling.  However it seems
> like your new updated pattern would fit use of cmpxchg() very nicely.

Hello Christoph,

Thanks for the review. I had a look at the spin lock implementation on
x86 and apparently on x86 spin locks are implemented as qspinlocks
(include/asm-generic/qspinlock.h). queued_spin_lock() already uses
atomic_cmpxchg_acquire(). Are you sure that replacing the spin lock
by cmpxchg() will yield a performance improvement?



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