From: Nicolas Pitre <nico@cam.org>
To: Linus Torvalds <torvalds@osdl.org>
Cc: David Howells <dhowells@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
linux-arch@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>,
mingo@redhat.com, Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH 1/12]: MUTEX: Implement mutexes
Date: Sat, 17 Dec 2005 20:29:58 -0500 (EST) [thread overview]
Message-ID: <Pine.LNX.4.64.0512172018410.26663@localhost.localdomain> (raw)
In-Reply-To: <Pine.LNX.4.64.0512171201200.3698@g5.osdl.org>
On Sat, 17 Dec 2005, Linus Torvalds wrote:
> Of the other architectures you list, only ARM is really important. And no,
> arm doesn't do swap. It does LL/SC (except they call it "ldrex/strex",
> which I assume stands for "load/store with reservation and X just because
> X is cool. Yeah, we're cool" (*)).
Well, if you really want to be honest, you have to consider that the
ldrex/strex instructions are available only on ARM architecture level 6
and above, or in other words with only about 1% of all ARM deployments
out there. The other 99% of actual ARM processors in the field only
have the atomic swap (swp) instruction which is insufficient for
implementing a counting semaphore (we therefore have to disable
interrupts, do the semaphore update and enable interrupts again which is
much slower than a swp-based mutex).
Nicolas
next prev parent reply other threads:[~2005-12-18 1:30 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-16 23:13 [PATCH 0/12]: MUTEX: Introduce mutex implementation David Howells
2005-12-16 23:13 ` [PATCH 2/12]: MUTEX: Provide SWAP-based mutex for FRV David Howells
2005-12-16 23:13 ` [PATCH 3/12]: MUTEX: Rename DECLARE_MUTEX for arch/ dir David Howells
2005-12-16 23:13 ` [PATCH 1/12]: MUTEX: Implement mutexes David Howells
2005-12-17 3:58 ` Steven Rostedt
2005-12-17 7:35 ` Linus Torvalds
2005-12-17 7:55 ` Nick Piggin
2005-12-17 12:36 ` Steven Rostedt
2005-12-17 19:21 ` David Howells
2005-12-17 20:11 ` Linus Torvalds
2005-12-17 21:44 ` Russell King
2005-12-18 1:29 ` Nicolas Pitre [this message]
2005-12-18 2:34 ` Linus Torvalds
2005-12-18 4:07 ` Nicolas Pitre
2005-12-18 4:18 ` Steven Rostedt
2005-12-18 6:30 ` Linus Torvalds
2005-12-18 9:26 ` Russell King
2005-12-18 18:42 ` Linus Torvalds
2005-12-18 19:41 ` James Bottomley
2005-12-18 19:54 ` Linus Torvalds
2005-12-19 1:48 ` Nicolas Pitre
2005-12-19 9:27 ` Russell King
2005-12-19 13:54 ` Matthew Wilcox
2005-12-19 15:49 ` Nicolas Pitre
2005-12-19 15:45 ` Nicolas Pitre
2005-12-18 17:29 ` Nicolas Pitre
2005-12-18 13:38 ` Alan Cox
2005-12-18 17:21 ` Nicolas Pitre
2005-12-16 23:13 ` [PATCH 9/12]: MUTEX: Rename DECLARE_MUTEX for net/ dir David Howells
2005-12-16 23:13 ` [PATCH 10/12]: MUTEX: Rename DECLARE_MUTEX for sound/ dir David Howells
2005-12-16 23:13 ` [PATCH 5/12]: MUTEX: Rename DECLARE_MUTEX for drivers/ dir, N thru Z David Howells
2005-12-16 23:13 ` [PATCH 11/12]: MUTEX: Rename DECLARE_MUTEX for miscellaneous directories David Howells
2005-12-16 23:13 ` [PATCH 7/12]: MUTEX: Rename DECLARE_MUTEX for include/asm-*/ dirs David Howells
2005-12-16 23:13 ` [PATCH 4/12]: MUTEX: Rename DECLARE_MUTEX for drivers/ dir, A thru M David Howells
2005-12-16 23:13 ` [PATCH 8/12]: MUTEX: Rename DECLARE_MUTEX for kernel/ dir David Howells
2005-12-16 23:13 ` [PATCH 6/12]: MUTEX: Rename DECLARE_MUTEX for fs/ dir David Howells
2005-12-16 23:13 ` [PATCH 12/12]: MUTEX: Provide synchronisation primitive testing module David Howells
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