From: Peter Zijlstra <peterz@infradead.org>
To: "Xu, Yanfei" <yanfei.xu@windriver.com>
Cc: mingo@redhat.com, longman@redhat.com, boqun.feng@gmail.com,
will@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Documentation/atomic_t: Document cmpxchg() vs try_cmpxchg()
Date: Mon, 5 Jul 2021 19:12:26 +0200 [thread overview]
Message-ID: <YOM9emXjk2aHYosu@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <137696c1-7782-18f0-f005-a2416edbeac0@windriver.com>
On Mon, Jul 05, 2021 at 11:25:29PM +0800, Xu, Yanfei wrote:
> > +CMPXHG vs TRY_CMPXCHG
>
> CMPXHG -> CMPXCHG
Yeah, already fixed. I spotted it a minute after sending :/
> > +---------------------
> > +
> > + int atomic_cmpxchg(atomic_t *ptr, int old, int new);
> > + bool atomic_try_cmpxchg(atomic_t *ptr, int *oldp, int new);
> > +
> > +Both provide the same functionality, but try_cmpxchg() can lead to more
> > +compact code. The functions relate like:
> > +
> > + bool atomic_try_cmpxchg(atomic_t *ptr, int *oldp, int new)
> > + {
> > + int ret, old = *oldp;
> > + ret = atomic_cmpxchg(ptr, old, new);
> > + if (ret != old)
> > + *oldp = ret;
> > + return ret == old;
> > + }
>
> I tried to search some comments about atomic_try_cmpxchg(), but failed.
> Maybe I missed it. With your this document, it is more clear now.
OK, good, thanks!
> > +
> > +and:
> > +
> > + int atomic_cmpxchg(atomic_t *ptr, int old, int new)
> > + {
> > + (void)atomic_try_cmpxchg(ptr, &old, new);
> > + return old;
> > + }
> > +
> > +Usage:
> > +
> > + old = atomic_read(&v); old = atomic_read(&v);
> > + for (;;) { do {
> > + new = func(old); new = func(old);
> > + tmp = atomic_cmpxchg(&v, old, new); } while (!atomic_try_cmpxchg(&v, &old, new));
>
> Some unnecessary spaces before "while".
That's due to the diff prepending the line with "+ " which offsets the
tabstop. If you apply the patch the actual document is fine.
next prev parent reply other threads:[~2021-07-05 17:12 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-30 15:35 [RFC][PATCH 0/4] locking/mutex: Some HANDOFF fixes Peter Zijlstra
2021-06-30 15:35 ` [RFC][PATCH 1/4] locking/mutex: Use try_cmpxchg() Peter Zijlstra
2021-07-05 11:59 ` Xu, Yanfei
2021-07-05 14:00 ` Peter Zijlstra
2021-07-05 14:52 ` Xu, Yanfei
2021-07-05 15:07 ` [PATCH] Documentation/atomic_t: Document cmpxchg() vs try_cmpxchg() Peter Zijlstra
2021-07-05 15:21 ` Will Deacon
2021-07-05 15:25 ` Xu, Yanfei
2021-07-05 17:12 ` Peter Zijlstra [this message]
2021-07-08 8:42 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2021-07-08 8:42 ` [tip: locking/core] locking/mutex: Use try_cmpxchg() tip-bot2 for Peter Zijlstra
2021-06-30 15:35 ` [RFC][PATCH 2/4] locking/mutex: Fix HANDOFF condition Peter Zijlstra
2021-07-08 8:42 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2021-06-30 15:35 ` [RFC][PATCH 3/4] locking/mutex: Introduce __mutex_trylock_or_handoff() Peter Zijlstra
2021-06-30 16:30 ` Waiman Long
2021-06-30 18:04 ` Peter Zijlstra
2021-07-08 8:42 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2021-06-30 15:35 ` [RFC][PATCH 4/4] locking/mutex: Add MUTEX_WARN_ON Peter Zijlstra
2021-07-08 8:42 ` [tip: locking/core] " tip-bot2 for Peter Zijlstra
2021-06-30 19:03 ` [RFC][PATCH 0/4] locking/mutex: Some HANDOFF fixes Waiman Long
2021-07-01 2:11 ` Xu, Yanfei
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