From: Martin Wirth <Martin.Wirth@dlr.de>
To: Rusty Russell <rusty@rustcorp.com.au>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Futexes IV (Fast Lightweight Userspace Semaphores)
Date: Wed, 13 Mar 2002 10:12:33 +0100 [thread overview]
Message-ID: <3C8F1801.6070107@dlr.de> (raw)
> > > On Tue, 12 Mar 2002, Rusty Russell wrote:
> > > > > > > You've convinced me.
> > > > > Damn. Because now I've been playing with a different approach.
> > > I don't think your current patch is very useful.
> I agree. But your "Applied" EMail rushed me into posting it.
The normal way to use multithreading under UNIX is the pthread
library. Here the condition variables are the equivalent to kernel
wait queues. So I think to really implement a fast pthread lib based
on futexes one needs some means to implement condition variables
(with synchronous futex release to implement pthread_cond_wait(..)!).
This could either be done with the exported waitqueue approach or a bit
easier (but less general) by associating a second hashed waitqueue with
each futex (maybe marked by the odd offset+1?). Then we would have two
additional variants of sys_futex (with parameters FUTEX_WAIT,
FUTEX_SIGNAL).
The principle implementation is:
FUTEX_WAIT:
add_to_cond_queue
current->state=INTERRUPTIBLE
futex_up
schedule
remove_from_cond_queue
futex_down
FUTEX_SIGNAL
wake_up_all on cond_queue
Later we may also want FUTEX_SIGNAL_ONE and FUTEX_WAIT_TIMEOUT.
The user space code for pthread_cond_wait then of course needs a
chaining of the protecting pthread_mutex and the futex used as condition
variable.
Martin
next reply other threads:[~2002-03-13 9:13 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-03-13 9:12 Martin Wirth [this message]
2002-03-13 19:41 ` [PATCH] Futexes IV (Fast Lightweight Userspace Semaphores) Bill Davidsen
2002-03-13 19:52 ` Dave McCracken
2002-03-13 22:17 ` Bill Davidsen
2002-03-13 20:06 ` Alan Cox
2002-03-15 7:31 ` Rusty Russell
2002-03-15 8:41 ` Martin Wirth
2002-03-15 15:29 ` Hubertus Franke
2002-03-15 16:23 ` Peter Wächtler
2002-03-16 0:12 ` Rusty Russell
2002-03-16 11:23 ` Martin Wirth
2002-03-18 0:52 ` Ulrich Drepper
2002-03-19 3:28 ` Rusty Russell
2002-03-19 4:05 ` Ulrich Drepper
2002-03-20 6:20 ` Rusty Russell
2002-03-20 10:42 ` Peter Wächtler
2002-03-20 17:20 ` Ulrich Drepper
2002-03-19 8:34 ` Martin Wirth
2002-03-20 6:45 ` Rusty Russell
2002-03-21 6:48 ` Martin Wirth
2002-03-24 18:25 ` Peter Wächtler
2002-03-25 2:28 ` Rusty Russell
2002-03-25 4:46 ` Rusty Russell
2002-03-25 11:56 ` Peter Wächtler
2002-03-26 1:02 ` Rusty Russell
2002-03-26 8:17 ` Martin Wirth
2002-03-26 23:10 ` Rusty Russell
2002-03-27 21:05 ` Hubertus Franke
2002-03-27 23:53 ` Rusty Russell
2002-03-25 9:47 ` Peter Wächtler
2002-03-16 19:48 ` Peter Wächtler
2002-03-17 6:50 ` Rusty Russell
-- strict thread matches above, loose matches on Subject: below --
2002-03-05 7:01 Rusty Russell
2002-03-05 22:39 ` Davide Libenzi
2002-03-05 23:16 ` Hubertus Franke
2002-03-05 23:26 ` Davide Libenzi
2002-03-05 23:37 ` Peter Svensson
2002-03-05 23:50 ` Davide Libenzi
2002-03-08 0:07 ` Richard Henderson
2002-03-06 1:46 ` Rusty Russell
2002-03-06 2:03 ` Davide Libenzi
2002-03-08 18:07 ` Linus Torvalds
2002-03-08 19:03 ` Hubertus Franke
2002-03-08 19:22 ` Linus Torvalds
2002-03-08 20:29 ` Hubertus Franke
2002-03-08 20:48 ` Matthew Kirkwood
2002-03-08 21:02 ` Linus Torvalds
2002-03-08 23:15 ` Hubertus Franke
2002-03-08 23:36 ` Alan Cox
2002-03-08 23:41 ` Linus Torvalds
2002-03-08 23:56 ` Hubertus Franke
2002-03-09 2:12 ` Linus Torvalds
2002-03-11 14:14 ` Hubertus Franke
2002-03-09 0:03 ` H. Peter Anvin
2002-03-09 1:15 ` Alan Cox
2002-03-10 19:41 ` Linus Torvalds
2002-03-11 20:49 ` Pavel Machek
2002-03-10 19:58 ` Martin J. Bligh
2002-03-10 20:40 ` Alan Cox
2002-03-10 20:28 ` Martin J. Bligh
2002-03-10 21:05 ` Alan Cox
2002-03-13 7:40 ` Rusty Russell
2002-03-13 16:37 ` Alan Cox
2002-03-12 9:35 ` Helge Hafting
2002-03-08 20:40 ` Alan Cox
2002-03-08 20:57 ` Linus Torvalds
2002-03-08 23:43 ` H. Peter Anvin
2002-03-08 22:55 ` Hubertus Franke
2002-03-08 23:38 ` Alan Cox
2002-03-08 23:44 ` H. Peter Anvin
2002-03-08 20:47 ` george anzinger
2002-03-08 23:02 ` Hubertus Franke
2002-03-08 23:47 ` george anzinger
2002-03-09 1:11 ` Alan Cox
2002-03-09 1:20 ` Linus Torvalds
2002-03-09 4:49 ` Rusty Russell
2002-03-11 22:45 ` Linus Torvalds
2002-03-11 23:12 ` Hubertus Franke
2002-03-12 7:20 ` Rusty Russell
2002-03-12 14:56 ` Hubertus Franke
2002-03-13 4:02 ` Rusty Russell
2002-03-12 17:17 ` Linus Torvalds
2002-03-13 2:57 ` Rusty Russell
2002-03-09 4:51 ` Rusty Russell
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=3C8F1801.6070107@dlr.de \
--to=martin.wirth@dlr.de \
--cc=linux-kernel@vger.kernel.org \
--cc=rusty@rustcorp.com.au \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).