From: Roman Penyaev <rpenyaev@suse.de>
To: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 1/1] epoll: use rwlock in order to reduce ep_poll_callback() contention
Date: Wed, 05 Dec 2018 12:25:39 +0100 [thread overview]
Message-ID: <51e8202b163d7522efb18aa2ca79d952@suse.de> (raw)
In-Reply-To: <20181204235907.GA5388@andrea>
On 2018-12-05 00:59, Andrea Parri wrote:
> Hi Roman,
>
> On Tue, Dec 04, 2018 at 12:50:58PM +0100, Roman Penyaev wrote:
>> On 2018-12-03 18:34, Linus Torvalds wrote:
>
>> > This also ends up making the memory ordering of "xchg()" very very
>> > important. Yes, we've documented it as being an ordering op, but I'm
>> > not sure we've relied on it this directly before.
>>
>> Seems exit_mm() does exactly the same, the following chunk:
>>
>> up_read(&mm->mmap_sem);
>>
>> self.task = current;
>> self.next = xchg(&core_state->dumper.next, &self);
>>
>>
>> At least code pattern looks similar.
>
> Maybe add a comment on top of (your) xchg() to note/justify these
> memory
> ordering requirements? As Paul said: "if there are races, this would
> help force them to happen" (and simplify the review, this/future).
Hi Andrea,
Sure, this path is tricky, so will I cook something up.
--
Roman
next prev parent reply other threads:[~2018-12-05 11:25 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-03 11:02 [RFC PATCH 1/1] epoll: use rwlock in order to reduce ep_poll_callback() contention Roman Penyaev
2018-12-03 17:34 ` Linus Torvalds
2018-12-04 11:50 ` Roman Penyaev
2018-12-04 23:59 ` Andrea Parri
2018-12-05 11:25 ` Roman Penyaev [this message]
2018-12-04 17:23 ` Jason Baron
2018-12-04 19:02 ` Paul E. McKenney
2018-12-05 11:22 ` Roman Penyaev
2018-12-05 11:16 ` Roman Penyaev
2018-12-05 16:38 ` Jason Baron
2018-12-05 20:11 ` Roman Penyaev
2018-12-06 1:54 ` Davidlohr Bueso
2018-12-06 3:08 ` Davidlohr Bueso
2018-12-06 10:27 ` Roman Penyaev
2018-12-06 4:04 ` Davidlohr Bueso
2018-12-06 10:25 ` Roman Penyaev
2018-12-05 23:46 ` Eric Wong
2018-12-06 10:52 ` Roman Penyaev
2018-12-06 20:35 ` Eric Wong
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