From: Will Deacon <[email protected]>
To: Peter Zijlstra <[email protected]>
Cc: "Jens Axboe" <[email protected]>,
"Carter Li 李通洲" <[email protected]>,
"Pavel Begunkov" <[email protected]>,
io-uring <[email protected]>,
"Oleg Nesterov" <[email protected]>,
"Mark Rutland" <[email protected]>,
[email protected]
Subject: Re: [PATCH] asm-generic/atomic: Add try_cmpxchg() fallbacks
Date: Thu, 20 Feb 2020 10:39:35 +0000 [thread overview]
Message-ID: <20200220103934.GA14459@willie-the-truck> (raw)
In-Reply-To: <[email protected]>
On Thu, Feb 20, 2020 at 11:37:27AM +0100, Peter Zijlstra wrote:
> On Thu, Feb 20, 2020 at 10:30:45AM +0000, Will Deacon wrote:
> > On Tue, Feb 18, 2020 at 03:27:00PM +0100, Peter Zijlstra wrote:
> > > diff --git a/scripts/atomic/gen-atomic-fallback.sh b/scripts/atomic/gen-atomic-fallback.sh
> > > index b6c6f5d306a7..3c9be8d550e0 100755
> > > --- a/scripts/atomic/gen-atomic-fallback.sh
> > > +++ b/scripts/atomic/gen-atomic-fallback.sh
> > > @@ -140,6 +140,32 @@ cat <<EOF
> > > EOF
> > > }
> > >
> > > +gen_try_cmpxchg_fallback()
> > > +{
> > > + local order="$1"; shift;
> > > +
> > > +cat <<EOF
> > > +#ifndef try_cmpxchg${order}
> > > +#define try_cmpxchg${order}(_ptr, _oldp, _new) \\
> > > +({ \\
> > > + typeof(*ptr) ___r, ___o = *(_oldp); \\
> > > + ___r = cmpxchg${order}((_ptr), ___o, (_new)); \\
> > > + if (unlikely(___r != ___o)) \\
> > > + *(_old) = ___r; \\
> >
> > This doesn't compile because _old isn't declared. Probably best to avoid
> > evaluating _oldp twice though.
>
> Compiler had already spotted that, I'll make it something like:
>
> typeof(*ptr) *___op = (_oldp), ___o = *___op;
>
> ...
>
> *___op = ___r;
>
> Which avoids the double eval.
Cool, you can stick my Ack on the patch with that change.
Will
next prev parent reply other threads:[~2020-02-20 10:39 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-12 16:31 [ISSUE] The time cost of IOSQE_IO_LINK Carter Li 李通洲
2020-02-12 17:11 ` Jens Axboe
2020-02-12 17:22 ` Jens Axboe
2020-02-12 17:29 ` Jens Axboe
2020-02-13 0:33 ` Carter Li 李通洲
2020-02-13 15:08 ` Pavel Begunkov
2020-02-13 15:14 ` Jens Axboe
2020-02-13 15:51 ` Carter Li 李通洲
2020-02-14 1:25 ` Carter Li 李通洲
2020-02-14 2:45 ` Jens Axboe
2020-02-14 5:03 ` Jens Axboe
2020-02-14 15:32 ` Peter Zijlstra
2020-02-14 15:47 ` Jens Axboe
2020-02-14 16:18 ` Jens Axboe
2020-02-14 17:52 ` Jens Axboe
2020-02-14 20:44 ` Jens Axboe
2020-02-15 0:16 ` Carter Li 李通洲
2020-02-15 1:10 ` Jens Axboe
2020-02-15 1:25 ` Carter Li 李通洲
2020-02-15 1:27 ` Jens Axboe
2020-02-15 6:01 ` Jens Axboe
2020-02-15 6:32 ` Carter Li 李通洲
2020-02-15 15:11 ` Jens Axboe
2020-02-16 19:06 ` Pavel Begunkov
2020-02-16 22:23 ` Jens Axboe
2020-02-17 10:30 ` Pavel Begunkov
2020-02-17 19:30 ` Jens Axboe
2020-02-16 23:06 ` Jens Axboe
2020-02-16 23:07 ` Jens Axboe
2020-02-17 12:09 ` Peter Zijlstra
2020-02-17 16:12 ` Jens Axboe
2020-02-17 17:16 ` Jens Axboe
2020-02-17 17:46 ` Peter Zijlstra
2020-02-17 18:16 ` Jens Axboe
2020-02-18 13:13 ` Peter Zijlstra
2020-02-18 14:27 ` [PATCH] asm-generic/atomic: Add try_cmpxchg() fallbacks Peter Zijlstra
2020-02-18 14:40 ` Peter Zijlstra
2020-02-20 10:30 ` Will Deacon
2020-02-20 10:37 ` Peter Zijlstra
2020-02-20 10:39 ` Will Deacon [this message]
2020-02-18 14:56 ` [ISSUE] The time cost of IOSQE_IO_LINK Oleg Nesterov
2020-02-18 15:07 ` Oleg Nesterov
2020-02-18 15:38 ` Peter Zijlstra
2020-02-18 16:33 ` Jens Axboe
2020-02-18 15:07 ` Peter Zijlstra
2020-02-18 15:50 ` [PATCH] task_work_run: don't take ->pi_lock unconditionally Oleg Nesterov
2020-02-20 16:39 ` Peter Zijlstra
2020-02-20 17:22 ` Oleg Nesterov
2020-02-20 17:49 ` Peter Zijlstra
2020-02-21 14:52 ` Oleg Nesterov
2020-02-24 18:47 ` Jens Axboe
2020-02-28 19:17 ` Jens Axboe
2020-02-28 19:25 ` Peter Zijlstra
2020-02-28 19:28 ` Jens Axboe
2020-02-28 20:06 ` Peter Zijlstra
2020-02-28 20:15 ` Jens Axboe
2020-02-18 16:46 ` [ISSUE] The time cost of IOSQE_IO_LINK Jens Axboe
2020-02-18 16:52 ` Jens Axboe
2020-02-18 13:13 ` Peter Zijlstra
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