From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>,
LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Luiz Capitulino <lcapitulino@redhat.com>,
Christoph Lameter <cl@linux.com>, Ingo Molnar <mingo@kernel.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 1/7] atomic: Export fetch_or()
Date: Wed, 25 Nov 2015 10:13:49 +0100 [thread overview]
Message-ID: <20151125091349.GW17308@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20151124211951.GA16609@lerouge>
On Tue, Nov 24, 2015 at 10:19:52PM +0100, Frederic Weisbecker wrote:
> Also note that or_return() means that you first do OR and then return the new value.
Yes, that's useless. OR is an irreversible operator, which means
or_return() looses data. You can never say if a bit included in the
mask was set before.
You really must have fetch_or().
next prev parent reply other threads:[~2015-11-25 9:14 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-13 14:22 [PATCH 0/7] nohz: Tick dependency mask v3 Frederic Weisbecker
2015-11-13 14:22 ` [PATCH 1/7] atomic: Export fetch_or() Frederic Weisbecker
2015-11-24 15:58 ` Chris Metcalf
2015-11-24 21:19 ` Frederic Weisbecker
2015-11-24 21:48 ` Chris Metcalf
2015-11-30 17:36 ` Frederic Weisbecker
2015-11-30 18:17 ` Chris Metcalf
2015-11-25 9:13 ` Peter Zijlstra [this message]
2015-11-13 14:22 ` [PATCH 2/7] nohz: New tick dependency mask Frederic Weisbecker
2015-11-24 16:19 ` Chris Metcalf
2015-11-25 11:32 ` Frederic Weisbecker
2015-12-01 20:41 ` Peter Zijlstra
2015-12-01 22:20 ` Frederic Weisbecker
2015-12-02 10:56 ` Peter Zijlstra
2015-12-02 14:08 ` Frederic Weisbecker
2015-12-02 15:09 ` Peter Zijlstra
2015-12-08 15:57 ` Frederic Weisbecker
2015-12-02 12:45 ` Peter Zijlstra
2015-12-02 14:10 ` Frederic Weisbecker
2015-12-02 12:48 ` Peter Zijlstra
2015-12-02 14:11 ` Frederic Weisbecker
2015-11-13 14:22 ` [PATCH 3/7] perf: Migrate perf to use new tick dependency mask model Frederic Weisbecker
2015-11-24 16:19 ` Chris Metcalf
2015-11-25 12:34 ` Frederic Weisbecker
2015-12-02 16:17 ` Peter Zijlstra
2015-12-02 17:03 ` Frederic Weisbecker
2015-12-02 17:15 ` Peter Zijlstra
2015-11-13 14:22 ` [PATCH 4/7] sched: Account rr and fifo tasks separately Frederic Weisbecker
2015-12-02 12:53 ` Peter Zijlstra
2015-12-02 14:16 ` Frederic Weisbecker
2015-11-13 14:22 ` [PATCH 5/7] sched: Migrate sched to use new tick dependency mask model Frederic Weisbecker
2015-11-13 14:22 ` [PATCH 6/7] posix-cpu-timers: Migrate " Frederic Weisbecker
2015-11-13 14:22 ` [PATCH 7/7] sched-clock: " Frederic Weisbecker
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