From: Will Deacon <will.deacon@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"Waiman.Long@hp.com" <Waiman.Long@hp.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"paulmck@linux.vnet.ibm.com" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v3 1/8] atomics: add acquire/release/relaxed variants of some atomic operations
Date: Mon, 27 Jul 2015 11:21:07 +0100 [thread overview]
Message-ID: <20150727102106.GD3358@arm.com> (raw)
In-Reply-To: <20150727091430.GP19282@twins.programming.kicks-ass.net>
On Mon, Jul 27, 2015 at 10:14:30AM +0100, Peter Zijlstra wrote:
> On Fri, Jul 24, 2015 at 03:04:34PM +0100, Will Deacon wrote:
> > This patch introduces three new ordering semantics for these operations:
> >
> > - *_relaxed: No ordering guarantees. This is similar to what we have
> > already for the non-return atomics (e.g. atomic_add).
> >
> > - *_acquire: ACQUIRE semantics, similar to smp_load_acquire.
> >
> > - *_release: RELEASE semantics, similar to smp_store_release.
>
> Do we want to further specify that for the RmW operations the Read/load
> will provide the acquire and the Write/store the release?
Yeah, that's not a bad idea, but if we add that then I probably need to
re-iterate the cmpxchg strangeness since a failed cmpxchg_acquire would
still not have barrier semantics with the current implementation even though
it must have performed a Read/load access.
Will
next prev parent reply other threads:[~2015-07-27 10:21 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-24 14:04 [PATCH v3 0/8] Add generic support for relaxed atomics Will Deacon
2015-07-24 14:04 ` Will Deacon
2015-07-24 14:04 ` [PATCH v3 1/8] atomics: add acquire/release/relaxed variants of some atomic operations Will Deacon
2015-07-27 9:14 ` Peter Zijlstra
2015-07-27 10:21 ` Will Deacon [this message]
2015-07-27 10:21 ` Will Deacon
2015-07-27 16:33 ` Will Deacon
2015-07-27 17:51 ` Peter Zijlstra
2015-07-24 14:04 ` [PATCH v3 2/8] asm-generic: rework atomic-long.h to avoid bulk code duplication Will Deacon
2015-07-24 14:04 ` [PATCH v3 3/8] asm-generic: add relaxed/acquire/release variants for atomic_long_t Will Deacon
2015-07-24 14:04 ` [PATCH v3 4/8] lockref: remove homebrew cmpxchg64_relaxed macro definition Will Deacon
2015-07-24 14:04 ` Will Deacon
2015-07-24 14:04 ` [PATCH v3 5/8] locking/qrwlock: implement queue_write_unlock using smp_store_release Will Deacon
2015-07-24 14:04 ` Will Deacon
2015-07-24 14:04 ` [PATCH v3 6/8] locking/qrwlock: make use of acquire/release/relaxed atomics Will Deacon
2015-07-24 14:04 ` Will Deacon
2015-07-24 14:04 ` [PATCH v3 7/8] include/llist: use linux/atomic.h instead of asm/cmpxchg.h Will Deacon
2015-07-24 14:04 ` Will Deacon
2015-07-24 14:04 ` [PATCH v3 8/8] ARM: atomics: define our SMP atomics in terms of _relaxed operations Will Deacon
2015-07-24 14:04 ` Will Deacon
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