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Date: Wed, 9 Sep 2015 18:43:24 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>, Eric Dumazet <eric.dumazet@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        Maciej =?utf-8?Q?=C5=BBenczykowski?= <maze@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/3] Revert "task_work: remove fifo ordering guarantee"
Message-ID: <20150909164324.GA5824@redhat.com>
References: <20150908171433.GA14573@redhat.com> <20150908171452.GA14599@redhat.com> <CA+55aFy-cd6T+VeFV8WhegZXawzEFZEKN2U44-xLJRB4ww4s4w@mail.gmail.com> <20150909131642.GA28537@redhat.com> <CA+55aFxWoAPot0vLYaXPazgyiYA9pJgCThnb9MX3P87U+J7pbQ@mail.gmail.com>
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On 09/09, Linus Torvalds wrote:
>
> On Wed, Sep 9, 2015 at 6:16 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > Again, rightly or not I believe that FIFO makes task_work_add() more useful.
> > Perhaps I am wrong, so far I can only provide the artificial examples...
>
> I'd rather wait until somebody has a real use case. I hate adding
> infrastructure for "what if.." scenarios. We're better off if we can
> make do with minimal semantics (ie "there are no guarantees except
> that the work will be done before returning to user space") than with
> stronger semantics that people then perhaps start depending on even if
> they didn't really need them.

OK, I see. Thanks.

At least you seem to agree with 1-2, so if Al takes these changes we
can easily reconsider 3/3 later, if/when we have the new user which
needs FIFO.

Oleg.