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SubjectRe: [PATCH] seqlock: Use while instead of if+goto in __read_seqcount_begin
On Thu, Apr 09, 2020 at 09:45:58PM +0800, Muchun Song wrote:
> The creators of the C language gave us the while keyword. Let's use
> that instead of synthesizing it from if+goto.
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
> include/linux/seqlock.h | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
> index 8b97204f35a77..7bdea019814ce 100644
> --- a/include/linux/seqlock.h
> +++ b/include/linux/seqlock.h
> @@ -125,12 +125,8 @@ static inline unsigned __read_seqcount_begin(const seqcount_t *s)
> {
> unsigned ret;
>
> -repeat:
> - ret = READ_ONCE(s->sequence);
> - if (unlikely(ret & 1)) {
> + while (unlikely((ret = READ_ONCE(s->sequence)) & 1))
> cpu_relax();
> - goto repeat;
> - }
> kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX);
> return ret;

Patch looks fine to me, but I'll leave it to Peter as I don't have a
preference either way.

Will

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