From: Peter Zijlstra <peterz@infradead.org>
To: Vineet Gupta <Vineet.Gupta1@synopsys.com>
Cc: Christoph Lameter <cl@linux.com>,
linux-mm@kvack.org, Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
Noam Camus <noamc@ezchip.com>,
stable@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-snps-arc@lists.infradead.org, linux-parisc@vger.kernel,
"James E.J. Bottomley" <jejb@parisc-linux.org>,
Helge Deller <deller@gmx.de>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
Subject: Re: [PATCH] mm: slub: Ensure that slab_unlock() is atomic
Date: Wed, 9 Mar 2016 11:31:43 +0100 [thread overview]
Message-ID: <20160309103143.GF25010@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160309101349.GJ6344@twins.programming.kicks-ass.net>
On Wed, Mar 09, 2016 at 11:13:49AM +0100, Peter Zijlstra wrote:
> ---
> Subject: bitops: Do not default to __clear_bit() for __clear_bit_unlock()
>
> __clear_bit_unlock() is a special little snowflake. While it carries the
> non-atomic '__' prefix, it is specifically documented to pair with
> test_and_set_bit() and therefore should be 'somewhat' atomic.
>
> Therefore the generic implementation of __clear_bit_unlock() cannot use
> the fully non-atomic __clear_bit() as a default.
>
> If an arch is able to do better; is must provide an implementation of
> __clear_bit_unlock() itself.
>
FWIW, we could probably undo this if we unified all the spinlock based
atomic ops implementations (there's a whole bunch doing essentially the
same), and special cased __clear_bit_unlock() for that.
Collapsing them is probably a good idea anyway, just a fair bit of
non-trivial work to figure out all the differences and if they matter
etc..
next prev parent reply other threads:[~2016-03-09 10:31 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1457447457-25878-1-git-send-email-vgupta@synopsys.com>
[not found] ` <alpine.DEB.2.20.1603080857360.4047@east.gentwo.org>
[not found] ` <56DEF3D3.6080008@synopsys.com>
[not found] ` <alpine.DEB.2.20.1603081438020.4268@east.gentwo.org>
2016-03-09 6:43 ` [PATCH] mm: slub: Ensure that slab_unlock() is atomic Vineet Gupta
2016-03-09 6:43 ` Vineet Gupta
2016-03-09 10:13 ` Peter Zijlstra
2016-03-09 10:13 ` Peter Zijlstra
2016-03-09 10:31 ` Peter Zijlstra [this message]
2016-03-09 10:31 ` Peter Zijlstra
2016-03-09 11:12 ` Vineet Gupta
2016-03-09 11:00 ` Vineet Gupta
2016-03-09 11:40 ` Peter Zijlstra
2016-03-09 11:40 ` Peter Zijlstra
2016-03-09 11:53 ` Vineet Gupta
2016-03-09 12:22 ` Peter Zijlstra
2016-03-09 12:22 ` Peter Zijlstra
2016-03-14 8:05 ` Vineet Gupta
2016-03-14 8:05 ` Vineet Gupta
2016-03-09 13:22 ` Vineet Gupta
2016-03-09 13:22 ` Vineet Gupta
2016-03-09 14:51 ` Peter Zijlstra
2016-03-09 14:51 ` Peter Zijlstra
2016-03-10 5:51 ` Vineet Gupta
2016-03-10 9:10 ` Peter Zijlstra
2016-03-10 9:10 ` Peter Zijlstra
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