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 v2] atomic: Fix bugs in 'fetch_or()' and rename it to 'xchg_or()'
Date: Tue, 15 Mar 2016 14:26:23 +0100 [thread overview]
Message-ID: <20160315132623.GZ6344@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160315122145.GA7225@gmail.com>
On Tue, Mar 15, 2016 at 01:21:45PM +0100, Ingo Molnar wrote:
> - Renaming fetch_or() to xchg_or(), recognizing that the semantics
> are xchg()-alike.
Let me add another argument for why I don't like the "exchange/swap
(and) add" naming.
Exchange (and swap) replace one value for another, like:
old = xchg(ptr, val);
Whatever was there, gets replaced by the independent value in @val.
Straight up replacement.
However with something like xchg_or, you don't do a direct replacement
with an unrelated value. Instead you modify the pre-existing value. So
there really isn't an exchange at all.
So "fetch (and) or" really describes the operation better. You load
(fetch) the value and then modify it, in an indivisible (aka atomic)
fashion.
next prev parent reply other threads:[~2016-03-15 13:26 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
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 [this message]
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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