From: Linus Torvalds <torvalds@osdl.org>
To: Hugh Dickins <hugh@veritas.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
Jamie Lokier <jamie@shareable.org>, Andrew Morton <akpm@osdl.org>,
Ingo Molnar <mingo@redhat.com>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Alternate futex non-page-pinning and COW fix
Date: Thu, 4 Sep 2003 08:40:14 -0700 (PDT) [thread overview]
Message-ID: <Pine.LNX.4.44.0309040837560.580-100000@home.osdl.org> (raw)
In-Reply-To: <Pine.LNX.4.44.0309041230020.3647-100000@localhost.localdomain>
On Thu, 4 Sep 2003, Hugh Dickins wrote:
>
> Isn't it the case that to use sys_futex (in the way it's intended),
> userspace needs write access to the futex? FUTEX_WAIT and FUTEX_WAKE
> are used (depending on condition) after decrementing or incrementing
> the futex in userspace. FUTEX_FD is not such a clear case, but again
> it appears that you'd use it for an async wait after decrementing.
> FUTEX_REQUEUE seems to be a move or remap, doesn't change the picture.
Yes.
We can certainly just document it as a nonsense op. All I care about is
that it is _consistently_ broken, and that people don't make read-only
MAP_SHARED do something it has never ever done before - differ from a
semantic standpoint.
> The particular case above: if it's !PROT_WRITE MAP_PRIVATE, I'm
> saying that's not an area you can manipulate mutexes in anyway;
However, the thing is, the case really can be a totally writable
MAP_PRIVATE that just hasn't been modified (and thus not COW'ed) _yet_.
But sure, we could just require that futex pages are dirty in this case.
Linus
next prev parent reply other threads:[~2003-09-04 15:40 UTC|newest]
Thread overview: 102+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-08-26 3:12 [PATCH 2/2] Futex non-page-pinning fix Rusty Russell
2003-08-26 4:06 ` Andrew Morton
2003-08-26 5:30 ` Ingo Molnar
2003-08-26 5:50 ` Andrew Morton
2003-08-26 5:58 ` Ingo Molnar
2003-08-26 6:14 ` Andrew Morton
2003-08-26 6:36 ` Ingo Molnar
2003-08-26 7:02 ` Andrew Morton
2003-08-26 7:56 ` Arjan van de Ven
2003-08-26 8:08 ` Muli Ben-Yehuda
2003-08-26 8:11 ` Arjan van de Ven
2003-08-26 8:25 ` Andrew Morton
2003-08-26 9:02 ` Muli Ben-Yehuda
2003-08-26 10:38 ` William Lee Irwin III
2003-08-26 10:44 ` Andrew Morton
2003-08-26 10:45 ` William Lee Irwin III
2003-08-26 17:29 ` Andrew Morton
2003-08-26 19:35 ` William Lee Irwin III
2003-08-27 5:17 ` Rusty Russell
2003-08-27 6:20 ` Andrew Morton
2003-08-28 0:47 ` Rusty Russell
2003-08-28 8:21 ` Andrew Morton
2003-08-29 3:46 ` Rusty Russell
2003-08-29 4:17 ` Andrew Morton
2003-08-30 7:49 ` Rusty Russell
2003-09-01 0:35 ` Jamie Lokier
2003-09-01 4:11 ` Rusty Russell
2003-09-01 20:57 ` Hugh Dickins
2003-09-02 3:12 ` Rusty Russell
2003-09-02 6:51 ` Jamie Lokier
2003-09-02 16:14 ` Hugh Dickins
2003-09-02 19:54 ` Jamie Lokier
2003-09-02 20:15 ` Andrew Morton
2003-09-02 21:20 ` Jamie Lokier
2003-09-03 2:40 ` Rusty Russell
2003-09-03 7:36 ` [PATCH] Alternate futex non-page-pinning and COW fix Jamie Lokier
2003-09-03 11:19 ` Hugh Dickins
2003-09-03 14:38 ` Jamie Lokier
2003-09-03 17:39 ` Jamie Lokier
2003-09-03 17:55 ` Linus Torvalds
2003-09-03 18:06 ` Hugh Dickins
2003-09-03 18:19 ` Linus Torvalds
2003-09-03 18:43 ` Hugh Dickins
2003-09-03 19:05 ` Linus Torvalds
2003-09-03 19:40 ` Hugh Dickins
2003-09-03 20:04 ` Linus Torvalds
2003-09-04 2:43 ` Rusty Russell
2003-09-04 8:28 ` Linus Torvalds
2003-09-04 12:20 ` Hugh Dickins
2003-09-04 15:40 ` Linus Torvalds [this message]
2003-09-04 16:55 ` Hugh Dickins
2003-09-04 18:38 ` Jamie Lokier
2003-09-04 18:46 ` Linus Torvalds
2003-09-04 20:04 ` Jamie Lokier
2003-09-04 21:49 ` Linus Torvalds
2003-09-04 22:10 ` Jamie Lokier
2003-09-04 17:16 ` Jamie Lokier
2003-09-04 17:38 ` Linus Torvalds
2003-09-04 18:42 ` Linus Torvalds
2003-09-04 18:42 ` Linus Torvalds
2003-09-05 3:55 ` Rusty Russell
2003-09-05 17:55 ` Jamie Lokier
2003-09-04 17:26 ` Jamie Lokier
2003-09-04 1:30 ` Rusty Russell
2003-09-04 21:00 ` Jamie Lokier
2003-09-05 5:19 ` Rusty Russell
2003-09-05 20:54 ` Jamie Lokier
2003-09-07 6:45 ` Rusty Russell
2003-09-07 13:20 ` Jamie Lokier
2003-09-08 1:49 ` Rusty Russell
2003-09-08 9:44 ` Jamie Lokier
2003-09-03 14:40 ` [PATCH 2] Little fixes to previous futex patch Jamie Lokier
2003-09-04 16:45 ` Hugh Dickins
2003-09-04 17:59 ` Jamie Lokier
2003-09-04 18:35 ` Hugh Dickins
2003-09-04 20:11 ` Jamie Lokier
2003-09-04 21:36 ` Hugh Dickins
2003-09-04 21:58 ` Jamie Lokier
2003-09-07 7:23 ` Ingo Molnar
2003-09-07 12:27 ` Hugh Dickins
2003-09-07 15:03 ` Jamie Lokier
2003-09-08 1:56 ` Rusty Russell
2003-09-07 13:00 ` Jamie Lokier
2003-09-08 3:32 ` Ingo Molnar
2003-09-08 9:33 ` Jamie Lokier
2003-09-08 9:57 ` Ingo Molnar
2003-09-05 4:56 ` Rusty Russell
2003-09-03 15:34 ` [PATCH] Alternate futex non-page-pinning and COW fix Andrew Morton
2003-09-03 17:16 ` Jamie Lokier
2003-09-04 1:35 ` Rusty Russell
2003-09-04 17:35 ` Jamie Lokier
2003-09-03 0:14 ` [PATCH 2/2] Futex non-page-pinning fix Rusty Russell
2003-09-03 1:16 ` Andrew Morton
2003-09-03 1:54 ` Dave Hansen
2003-09-03 2:54 ` Andrew Morton
2003-09-02 3:23 ` Hugh Dickins
2003-09-02 23:58 ` Rusty Russell
2003-08-27 8:37 ` Hugh Dickins
2003-08-27 8:56 ` William Lee Irwin III
2003-08-27 10:38 ` Andrew Morton
2003-08-27 10:57 ` Hugh Dickins
2003-08-28 8:03 ` Rusty Russell
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