From: "Ulrich Drepper" <drepper@gmail.com>
To: "Davi Arnaut" <davi@haxent.com.br>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
"Davide Libenzi" <davidel@xmailserver.org>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [patch 14/22] pollfs: pollable futex
Date: Wed, 2 May 2007 09:46:53 -0700 [thread overview]
Message-ID: <a36005b50705020946x6cc1cb96r9ddd2b364ba168d7@mail.gmail.com> (raw)
In-Reply-To: <46388677.4050706@haxent.com.br>
On 5/2/07, Davi Arnaut <davi@haxent.com.br> wrote:
> It's quite easy to implement this scheme by write()ing the futexes all
> at once but that would break the one futex per fd association. For
> atomicity: if one of the futexes can't be queued, we would rollback
> (unqueue) the others.
>
> Sounds sane?
I don't know how you use "unqueue" in this context. If a queued futex
is one which is /locked/ by te call, then yes, this is the semantics
needed. Atomically locking a number of futexes means that if one of
the set cannot be locked all operations done to lock the others have
to be undone. It's an all-or-nothing situation.
Locking is not as easy as you might think, though. For non-PI futexes
there is deliberately no protocol in place describing what "locked"
means. The locking operation has to be customizable. This is what
the FUTEX_OP_* stuff is about.
And you wrote that currently each futex needs its own file descriptor.
So this would have to be changed, too.
next prev parent reply other threads:[~2007-05-02 16:46 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-02 5:22 [patch 00/22] pollfs: filesystem abstraction for pollable objects Davi Arnaut
2007-05-02 5:22 ` [patch 01/22] pollfs: kernel-side API header Davi Arnaut
2007-05-02 5:22 ` [patch 02/22] pollfs: file system operations Davi Arnaut
2007-05-02 5:22 ` [patch 03/22] pollfs: asynchronously wait for a signal Davi Arnaut
2007-05-02 5:22 ` [patch 04/22] pollfs: pollable signal Davi Arnaut
2007-05-02 5:22 ` [patch 05/22] pollfs: pollable signal compat code Davi Arnaut
2007-05-02 5:22 ` [patch 06/22] pollfs: export the plsignal system call Davi Arnaut
2007-05-02 5:22 ` [patch 07/22] pollfs: x86, wire up " Davi Arnaut
2007-05-02 5:22 ` [patch 08/22] pollfs: x86_64, " Davi Arnaut
2007-05-02 5:22 ` [patch 09/22] pollfs: pollable hrtimers Davi Arnaut
2007-05-02 21:16 ` Thomas Gleixner
2007-05-02 23:00 ` Davi Arnaut
2007-05-02 5:22 ` [patch 10/22] pollfs: export the pltimer system call Davi Arnaut
2007-05-02 5:22 ` [patch 11/22] pollfs: x86, wire up " Davi Arnaut
2007-05-02 5:22 ` [patch 12/22] pollfs: x86_64, " Davi Arnaut
2007-05-02 5:22 ` [patch 13/22] pollfs: asynchronous futex wait Davi Arnaut
2007-05-02 5:22 ` [patch 14/22] pollfs: pollable futex Davi Arnaut
2007-05-02 5:54 ` Eric Dumazet
2007-05-02 6:16 ` Davi Arnaut
2007-05-02 6:39 ` Eric Dumazet
2007-05-02 6:54 ` Davi Arnaut
2007-05-02 7:11 ` Davi Arnaut
2007-05-02 7:40 ` Ulrich Drepper
2007-05-02 7:55 ` Eric Dumazet
2007-05-02 8:08 ` Ulrich Drepper
2007-05-02 8:49 ` Eric Dumazet
2007-05-02 16:39 ` Ulrich Drepper
2007-05-02 16:59 ` Davi Arnaut
2007-05-02 17:10 ` Ulrich Drepper
2007-05-02 17:29 ` Davide Libenzi
2007-05-02 17:53 ` Ulrich Drepper
2007-05-02 18:21 ` Davide Libenzi
2007-05-03 13:46 ` Ulrich Drepper
2007-05-03 18:24 ` Davide Libenzi
2007-05-03 19:03 ` Ulrich Drepper
2007-05-03 22:14 ` Davide Libenzi
2007-05-04 15:28 ` Ulrich Drepper
2007-05-04 19:15 ` Davide Libenzi
2007-05-04 19:20 ` 2.6.20.4 / 2.6.21.1 AT91SAM9260-EK oops Ryan Ordway
2007-05-04 23:38 ` [patch 14/22] pollfs: pollable futex Ulrich Drepper
2007-05-05 18:54 ` Davide Libenzi
2007-05-06 7:50 ` Ulrich Drepper
2007-05-06 19:47 ` Davide Libenzi
2007-05-06 19:54 ` Andrew Morton
2007-05-06 20:18 ` Davide Libenzi
2007-05-06 21:57 ` Davi Arnaut
2007-05-07 5:33 ` Ulrich Drepper
2007-05-07 5:46 ` Ulrich Drepper
2007-05-02 17:37 ` Davi Arnaut
2007-05-02 17:49 ` Ulrich Drepper
2007-05-02 18:05 ` Davi Arnaut
2007-05-03 13:40 ` Ulrich Drepper
2007-05-02 12:20 ` Davi Arnaut
2007-05-02 12:39 ` Davi Arnaut
2007-05-02 16:46 ` Ulrich Drepper [this message]
2007-05-02 17:05 ` Davi Arnaut
2007-05-02 5:22 ` [patch 15/22] pollfs: export the plfutex system call Davi Arnaut
2007-05-02 5:22 ` [patch 16/22] pollfs: x86, wire up " Davi Arnaut
2007-05-02 5:22 ` [patch 17/22] pollfs: x86_64, " Davi Arnaut
2007-05-02 5:22 ` [patch 18/22] pollfs: check if a AIO event ring is empty Davi Arnaut
2007-05-02 5:22 ` [patch 19/22] pollfs: pollable aio Davi Arnaut
2007-05-02 5:22 ` [patch 20/22] pollfs: export the plaio system call Davi Arnaut
2007-05-02 5:22 ` [patch 21/22] pollfs: x86, wire up " Davi Arnaut
2007-05-02 5:22 ` [patch 22/22] pollfs: x86_64, " Davi Arnaut
2007-05-02 6:05 ` [patch 00/22] pollfs: filesystem abstraction for pollable objects Andrew Morton
2007-05-02 17:28 ` Davide Libenzi
2007-05-02 17:47 ` Davi Arnaut
2007-05-02 18:23 ` Davide Libenzi
2007-05-02 18:50 ` Davi Arnaut
2007-05-02 19:42 ` Davide Libenzi
2007-05-02 20:11 ` Davi Arnaut
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