From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: "Linus Torvalds" <torvalds@linux-foundation.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Frédéric Weisbecker" <fweisbec@gmail.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Andrew Morton" <akpm@linux-foundation.org>
Subject: Re: [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to 'xchg_or()'
Date: Tue, 15 Mar 2016 11:50:08 +0100 [thread overview]
Message-ID: <20160315105008.GT6344@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160315093245.GA7943@gmail.com>
On Tue, Mar 15, 2016 at 10:32:45AM +0100, Ingo Molnar wrote:
> 2) its naming sucks. "fetch_or()" does not really signal that it's a
> fundamentally atomic operation, nor what API family it belongs to.
I disagree there, the fetch-$op naming is widely used for atomic
operations that return the previous value. See for example the C/C++11
atomic ops.
I've even thought about reworking our entire atomic*_t bits to match.
That is, introduce all the fetch_$op primitives, then convert all the
$op_return ones over and finally remove all the $op_return ones.
I've not done so because we're all so very used to $op_return that I'm
sure people (and this would very much include me) would curse me for
changing this.
The reason for fetch_$op is that it also works for irreversible
operations like or. With or_return you simply cannot tell what the
previous state was (with add_return you can do a simple subtraction to
revert to the prior state).
And yes, some people use the xchg-$op naming, but its less widely used
(x86 asm being one). Other also use swap-$op.
In any case, I prefer the name as it was.
next prev parent reply other threads:[~2016-03-15 10:51 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-14 12:32 [GIT PULL] NOHZ updates for v4.6 Ingo Molnar
2016-03-15 2:44 ` Linus Torvalds
2016-03-15 8:42 ` Peter Zijlstra
2016-03-15 9:49 ` Ingo Molnar
2016-03-15 9:32 ` [PATCH] atomic: Fix bugs in 'fetch_or()' and rename it to 'xchg_or()' Ingo Molnar
2016-03-15 10:50 ` Peter Zijlstra [this message]
2016-03-15 12:08 ` Ingo Molnar
2016-03-15 12:42 ` Peter Zijlstra
2016-03-15 11:06 ` Peter Zijlstra
2016-03-15 11:59 ` Peter Zijlstra
2016-03-15 12:01 ` Ingo Molnar
2016-03-15 12:32 ` Ingo Molnar
2016-03-15 12:37 ` Ingo Molnar
2016-03-15 13:17 ` Peter Zijlstra
2016-03-15 12:21 ` [PATCH v2] " Ingo Molnar
2016-03-15 13:26 ` Peter Zijlstra
2016-03-16 8:04 ` Ingo Molnar
2016-03-16 8:29 ` Peter Zijlstra
2016-03-15 17:08 ` Frederic Weisbecker
2016-03-16 8:14 ` Ingo Molnar
2016-03-17 0:54 ` Frederic Weisbecker
2016-03-15 16:18 ` [PATCH] " Linus Torvalds
2016-03-15 9:53 ` [PATCH] nohz: Change tick_dep_mask from 'unsigned long' to 'unsigned int' Ingo Molnar
2016-03-15 12:15 ` Ingo Molnar
2016-03-15 16:30 ` Linus Torvalds
2016-03-15 17:28 ` Frederic Weisbecker
2016-03-15 17:36 ` Linus Torvalds
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