Re: [PATCH RESEND] sbitmap: Use atomic_{,long}_try_cmpxchg in sbitmap.c

Jens Axboe
2022-09-08T14:41:39Z

On 9/7/22 12:21 PM, Uros Bizjak wrote:
> Use atomic_long_try_cmpxchg instead of
> atomic_long_cmpxchg (*ptr, old, new) == old in __sbitmap_queue_get_batch
> and atomic_try_cmpxchg instead of atomic_cmpxchg (*ptr, old, new) == old
> in __sbq_wake_up. x86 CMPXCHG instruction returns success in ZF flag, so
> this change saves a compare after cmpxchg (and related move instruction
> in front of cmpxchg).
>
> Also, atomic_long_cmpxchg implicitly assigns old *ptr value to "old"
> when cmpxchg fails, enabling further code simplifications, e.g.
> an extra memory read can be avoided in the loop.
>
> No functional change intended.

It doesn't apply to the current tree, can you please resend one against
for-6.1/block?

--
Jens Axboe