From: Will Deacon <will.deacon@arm.com>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Waiman Long <waiman.long@hp.com>,
Davidlohr Bueso <dave@stgolabs.net>
Subject: Re: [PATCH v3 6/6] powerpc: atomic: Implement cmpxchg{,64}_* and atomic{,64}_cmpxchg_* variants
Date: Tue, 13 Oct 2015 16:04:27 +0100 [thread overview]
Message-ID: <20151013150427.GP21550@arm.com> (raw)
In-Reply-To: <20151013145830.GC23991@fixme-laptop.cn.ibm.com>
On Tue, Oct 13, 2015 at 10:58:30PM +0800, Boqun Feng wrote:
> On Tue, Oct 13, 2015 at 03:43:33PM +0100, Will Deacon wrote:
> > Putting a barrier in the middle of that critical section is probably a
> > terrible idea, and that's why I thought you were avoiding it (hence my
>
> The fact is that I haven't thought of that way to implement
> cmpxchg_release before you ask that question ;-) And I'm not going to do
> that for now and probably not in the future.
>
> > original question). Perhaps just add a comment to that effect, since I
>
> Are you suggesting if I put a barrier in the middle I'd better to add a
> comment, right? So if I don't do that, it's OK to let this patch as it.
No, I mean put a comment in your file to explain the reason why you
override _relaxed and _acquire, but not _release (because overriding
_release would introduce this weird barrier in the middle of the critical
section, which would likely cause the conditional store to fail).
Will
next prev parent reply other threads:[~2015-10-13 15:04 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-12 14:14 [PATCH v3 0/6] atomics: powerpc: Implement relaxed/acquire/release variants of some atomics Boqun Feng
2015-10-12 14:14 ` [PATCH v3 1/6] powerpc: atomic: Make *xchg and *cmpxchg a full barrier Boqun Feng
2015-10-12 14:23 ` Boqun Feng
2015-10-12 14:14 ` [PATCH v3 2/6] atomics: Add test for atomic operations with _relaxed variants Boqun Feng
2015-10-12 14:14 ` [PATCH v3 3/6] atomics: Allow architectures to define their own __atomic_op_* helpers Boqun Feng
2015-10-12 14:14 ` [PATCH v3 4/6] powerpc: atomic: Implement atomic{, 64}_*_return_* variants Boqun Feng
2015-10-13 13:21 ` Will Deacon
2015-10-13 13:35 ` Boqun Feng
2015-10-14 1:00 ` Boqun Feng
2015-10-12 14:14 ` [PATCH v3 5/6] powerpc: atomic: Implement xchg_* and atomic{, 64}_xchg_* variants Boqun Feng
2015-10-12 14:14 ` [PATCH v3 6/6] powerpc: atomic: Implement cmpxchg{, 64}_* and atomic{, 64}_cmpxchg_* variants Boqun Feng
2015-10-13 13:24 ` [PATCH v3 6/6] powerpc: atomic: Implement cmpxchg{,64}_* and atomic{,64}_cmpxchg_* variants Will Deacon
2015-10-13 14:32 ` Boqun Feng
2015-10-13 14:43 ` Will Deacon
2015-10-13 14:58 ` Boqun Feng
2015-10-13 15:04 ` Will Deacon [this message]
2015-10-13 15:45 ` Boqun Feng
2015-10-14 1:47 ` Boqun Feng
2015-10-14 9:40 ` Will Deacon
2015-10-13 14:46 ` Boqun Feng
2015-10-12 14:30 ` [PATCH RESEND v3 1/6] powerpc: atomic: Make *xchg and *cmpxchg a full barrier Boqun Feng
2015-10-14 0:10 ` Michael Ellerman
2015-10-14 0:51 ` Boqun Feng
2015-10-14 8:06 ` Peter Zijlstra
2015-10-14 9:26 ` Boqun Feng
2015-10-14 9:33 ` Peter Zijlstra
2015-10-14 9:43 ` Michael Ellerman
2015-10-13 12:27 ` [PATCH v3 0/6] atomics: powerpc: Implement relaxed/acquire/release variants of some atomics Peter Zijlstra
2015-10-13 15:46 ` Paul E. McKenney
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