linux-kernel - Re: [PATCH 3/3] Revert "task_work: remove fifo ordering guarantee"

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Message-ID: <CA+55aFwO=ZLnfkK9CcM3aaHh87F79NbfDPswmMmRh_9DTpHGew@mail.gmail.com>
Date:	Tue, 8 Sep 2015 10:41:30 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Maciej Żenczykowski <maze@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] Revert "task_work: remove fifo ordering guarantee"

On Tue, Sep 8, 2015 at 10:39 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> The other patches I do like - why add those list operations that are
> just guaranteed to mess up the cache to add the file descriptors to
> the workqueue list, when we can just do the operation directly?

Side note, it's not just messing with the cache unnecessarily when the
lists grow long, the "cmpxchg" involved in adding the work is fairly
expensive. It may be an unlocked operation, but it's generally as
expensive as a locked one - just without the possibility of a
deadlock.

               Linus
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