From: Andrew Morton <akpm@osdl.org>
To: David Howells <dhowells@redhat.com>
Cc: torvalds@osdl.org, hch@infradead.org, arjan@infradead.org,
matthew@wil.cx, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org
Subject: Re: [PATCH 1/19] MUTEX: Introduce simple mutex implementation
Date: Mon, 12 Dec 2005 16:19:44 -0800 [thread overview]
Message-ID: <20051212161944.3185a3f9.akpm@osdl.org> (raw)
In-Reply-To: <dhowells1134431145@warthog.cambridge.redhat.com>
David Howells <dhowells@redhat.com> wrote:
>
> The attached patch introduces a simple mutex implementation as an alternative
> to the usual semaphore implementation where simple mutex functionality is all
> that is required.
>
> This is useful in two ways:
>
> (1) A number of archs only provide very simple atomic instructions (such as
> XCHG on i386, TAS on M68K, SWAP on FRV) which aren't sufficient to
> implement full semaphore support directly. Instead spinlocks must be
> employed to implement fuller functionality.
>
> (2) This makes it obvious in what way the semaphore is being used: whether
> it's being used as a mutex or being used as a counter.
>
> This patch set does the following:
>
> (1) Provides a simple xchg() based semaphore as a default for all
> architectures that don't wish to override it and provide their own.
>
> Overriding is possible by setting CONFIG_ARCH_IMPLEMENTS_MUTEX and
> supplying asm/mutex.h
>
> Partial overriding is possible by #defining mutex_grab(), mutex_release()
> and is_mutex_locked() to perform the appropriate optimised functions.
>
> (2) Provides linux/mutex.h as a common include for gaining access to mutex
> semaphores.
>
> (3) Provides linux/semaphore.h as a common include for gaining access to all
> the different types of semaphore that may be used from within the kernel.
>
> (4) Renames down*() to down_sem*() and up() to up_sem() for the traditional
> semaphores, and removes init_MUTEX*() and DECLARE_MUTEX*() from
> asm/semaphore.h
>
> (5) Redirects the following to apply to the new mutexes rather than the
> traditional semaphores:
>
> down()
> down_trylock()
> down_interruptible()
> up()
> init_MUTEX()
> init_MUTEX_LOCKED()
> DECLARE_MUTEX()
> DECLARE_MUTEX_LOCKED()
>
> On the basis that most usages of semaphores are as mutexes, this makes
> sense for in most cases it's just then a matter of changing the type from
> struct semaphore to struct mutex. In some cases, sema_init() has to be
> changed to init_MUTEX*() also.
>
> (6) Generally include linux/semaphore.h in place of asm/semaphore.h.
>
> (7) Provides a debugging config option CONFIG_DEBUG_MUTEX_OWNER by which the
> mutex owner can be tracked and by which over-upping can be detected.
Maybe I'm not understanding all this, but...
I'd have thought that the way to do this is to simply reimplement down(),
up(), down_trylock(), etc using the new xchg-based code and to then hunt
down those few parts of the kernel which actually use the old semaphore's
counting feature and convert them to use down_sem(), up_sem(), etc. And
rename all the old semaphore code: s/down/down_sem/etc.
So after such a transformation, this new "mutex" thingy would not exist.
> include/linux/mutex.h | 32 +++++++
But it does.
> +#define mutex_grab(mutex) (xchg(&(mutex)->state, 1) == 0)
mutex_trylock(), please.
> +#define is_mutex_locked(mutex) ((mutex)->state)
Let's keep the namespace consistent. mutex_is_locked().
> +static inline void down(struct mutex *mutex)
> +{
> + if (mutex_grab(mutex)) {
likely()
> +#ifdef CONFIG_DEBUG_MUTEX_OWNER
> + mutex->__owner = current;
> +#endif
> + }
> + else {
> + __down(mutex);
> + }
> +}
> +
> +/*
> + * sleep interruptibly until we get the mutex
> + * - return 0 if successful, -EINTR if interrupted
> + */
> +static inline int down_interruptible(struct mutex *mutex)
> +{
> + if (mutex_grab(mutex)) {
likely()
> +static inline int down_trylock(struct mutex *mutex)
> +{
> + if (mutex_grab(mutex)) {
etc.
You could just put likely() into mutex_trylock(). err, mutex_grab().
> +/*
> + * release the mutex
> + */
> +static inline void up(struct mutex *mutex)
> +{
> + unsigned long flags;
> +
> +#ifdef CONFIG_DEBUG_MUTEX_OWNER
> + if (mutex->__owner != current)
> + __up_bad(mutex);
> + mutex->__owner = NULL;
> +#endif
> +
> + /* must prevent a race */
> + spin_lock_irqsave(&mutex->wait_lock, flags);
> + if (!list_empty(&mutex->wait_list))
> + __up(mutex);
> + else
> + mutex_release(mutex);
> + spin_unlock_irqrestore(&mutex->wait_lock, flags);
> +}
This is too large to inline.
It's also significantly slower than the existing up()?
next prev parent reply other threads:[~2005-12-13 0:18 UTC|newest]
Thread overview: 249+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-12 23:45 [PATCH 1/19] MUTEX: Introduce simple mutex implementation David Howells
2005-12-12 23:45 ` [PATCH 2/19] MUTEX: i386 arch mutex David Howells
2005-12-12 23:45 ` [PATCH 8/19] MUTEX: Drivers I-K changes David Howells
2005-12-12 23:45 ` [PATCH 7/19] MUTEX: Drivers F-H changes David Howells
2005-12-12 23:45 ` [PATCH 6/19] MUTEX: Drivers A-E changes David Howells
2005-12-12 23:45 ` [PATCH 3/19] MUTEX: x86_64 arch mutex David Howells
2005-12-12 23:45 ` [PATCH 5/19] MUTEX: Core kernel changes David Howells
2005-12-12 23:45 ` [PATCH 4/19] MUTEX: FRV arch mutex David Howells
2005-12-12 23:45 ` [PATCH 15/19] MUTEX: Second set of include changes David Howells
2005-12-12 23:45 ` [PATCH 10/19] MUTEX: Drivers N-P changes David Howells
2005-12-12 23:45 ` [PATCH 9/19] MUTEX: Drivers L-M changes David Howells
2005-12-12 23:45 ` [PATCH 13/19] MUTEX: Filesystem changes David Howells
2005-12-12 23:45 ` [PATCH 14/19] MUTEX: First set of include changes David Howells
2005-12-12 23:45 ` [PATCH 12/19] MUTEX: Drivers T-Z changes David Howells
2005-12-12 23:45 ` [PATCH 11/19] MUTEX: Drivers Q-S changes David Howells
2005-12-12 23:45 ` [PATCH 18/19] MUTEX: Security changes David Howells
2005-12-12 23:45 ` [PATCH 17/19] MUTEX: Networking changes David Howells
2005-12-12 23:45 ` [PATCH 16/19] MUTEX: IPC changes David Howells
2005-12-12 23:45 ` [PATCH 19/19] MUTEX: Sound changes David Howells
2005-12-13 0:13 ` [PATCH 1/19] MUTEX: Introduce simple mutex implementation Nick Piggin
2005-12-13 0:19 ` Nick Piggin
2005-12-13 0:19 ` Andrew Morton [this message]
2005-12-13 7:54 ` Ingo Molnar
2005-12-13 7:58 ` Andi Kleen
2005-12-13 8:42 ` Andrew Morton
2005-12-13 8:49 ` Andi Kleen
2005-12-13 9:01 ` Andrew Morton
2005-12-13 9:02 ` Andrew Morton
2005-12-13 10:07 ` Jakub Jelinek
2005-12-13 10:11 ` Andi Kleen
2005-12-13 10:15 ` Jakub Jelinek
2005-12-13 10:25 ` Andrew Morton
2005-12-14 10:46 ` Russell King
2005-12-13 9:05 ` Andi Kleen
2005-12-13 9:15 ` Andrew Morton
2005-12-13 9:24 ` Andi Kleen
2005-12-13 9:44 ` Andrew Morton
2005-12-13 9:49 ` Andi Kleen
2005-12-13 10:28 ` Andreas Schwab
2005-12-13 10:30 ` Andi Kleen
2005-12-13 12:33 ` Matthew Wilcox
2005-12-13 22:18 ` Adrian Bunk
2005-12-13 22:25 ` Andi Kleen
2005-12-13 22:32 ` Adrian Bunk
2005-12-13 9:11 ` Ingo Molnar
2005-12-13 9:04 ` Christoph Hellwig
2005-12-13 9:13 ` Ingo Molnar
2005-12-13 10:11 ` Jakub Jelinek
2005-12-13 10:19 ` Christoph Hellwig
2005-12-13 10:27 ` Ingo Molnar
2005-12-15 4:53 ` Miles Bader
2005-12-15 5:05 ` Nick Piggin
2005-12-13 9:09 ` Ingo Molnar
2005-12-13 9:21 ` Andi Kleen
2005-12-13 16:16 ` Linus Torvalds
2005-12-13 21:56 ` Using C99 in the kernel was " Andi Kleen
2005-12-13 23:05 ` Al Viro
2005-12-13 23:41 ` Andi Kleen
2005-12-13 9:03 ` Christoph Hellwig
2005-12-13 9:14 ` Andrew Morton
2005-12-13 9:21 ` Christoph Hellwig
2005-12-13 10:31 ` drivers/scsi/sd.c gcc-2.95.3 Alexey Dobriyan
2005-12-13 8:00 ` [PATCH 1/19] MUTEX: Introduce simple mutex implementation Arjan van de Ven
2005-12-13 9:03 ` Ingo Molnar
2005-12-13 9:09 ` Andi Kleen
2005-12-13 9:34 ` Ingo Molnar
2005-12-13 14:33 ` Mark Lord
2005-12-13 14:45 ` Arjan van de Ven
2005-12-13 9:37 ` Ingo Molnar
2005-12-13 9:19 ` Arjan van de Ven
2005-12-13 9:02 ` Christoph Hellwig
2005-12-13 9:39 ` Ingo Molnar
2005-12-13 10:00 ` Ingo Molnar
2005-12-13 17:40 ` Paul Jackson
2005-12-13 18:34 ` David Howells
2005-12-13 22:31 ` Paul Jackson
2005-12-14 11:02 ` David Howells
2005-12-14 11:12 ` David Howells
2005-12-14 11:18 ` Alan Cox
2005-12-14 12:35 ` David Howells
2005-12-14 13:58 ` Thomas Gleixner
2005-12-14 23:40 ` Mark Lord
2005-12-14 23:54 ` Andrew Morton
2005-12-15 13:41 ` Nikita Danilov
2005-12-15 14:56 ` Alan Cox
2005-12-15 15:52 ` Nikita Danilov
2005-12-15 16:50 ` Christopher Friesen
2005-12-15 20:53 ` Steven Rostedt
2005-12-15 15:55 ` David Howells
2005-12-15 16:22 ` linux-os (Dick Johnson)
2005-12-15 16:28 ` Linus Torvalds
2005-12-15 17:04 ` Thomas Gleixner
2005-12-15 17:09 ` Paul Jackson
2005-12-15 17:17 ` David Howells
2005-12-15 16:51 ` David Howells
2005-12-15 16:56 ` Paul Jackson
2005-12-15 17:28 ` David Howells
2005-12-15 17:48 ` Linus Torvalds
2005-12-15 18:20 ` Nikita Danilov
2005-12-15 20:58 ` Steven Rostedt
2005-12-15 19:21 ` Andrew Morton
2005-12-15 19:38 ` Linus Torvalds
2005-12-15 20:28 ` Steven Rostedt
2005-12-15 20:32 ` Geert Uytterhoeven
2005-12-16 21:41 ` Thomas Gleixner
2005-12-16 21:41 ` Linus Torvalds
2005-12-16 22:06 ` Thomas Gleixner
2005-12-16 22:19 ` Linus Torvalds
2005-12-16 22:32 ` Steven Rostedt
2005-12-16 22:42 ` Thomas Gleixner
2005-12-16 22:41 ` Linus Torvalds
2005-12-16 22:49 ` Steven Rostedt
2005-12-16 23:29 ` Thomas Gleixner
2005-12-17 0:29 ` Joe Korty
2005-12-17 1:00 ` Linus Torvalds
2005-12-17 3:13 ` Steven Rostedt
2005-12-17 7:34 ` Linus Torvalds
2005-12-17 23:43 ` Matthew Wilcox
2005-12-18 0:05 ` Lee Revell
2005-12-18 0:21 ` Matthew Wilcox
2005-12-18 1:25 ` Lee Revell
2005-12-22 12:27 ` Bill Huey
2005-12-19 16:08 ` Ingo Molnar
2005-12-22 12:40 ` Bill Huey
2005-12-22 12:45 ` Bill Huey
2005-12-19 23:46 ` Keith Owens
2005-12-15 14:41 ` Steven Rostedt
2005-12-14 23:57 ` Thomas Gleixner
2005-12-14 23:57 ` Mark Lord
2005-12-15 0:10 ` Thomas Gleixner
2005-12-15 2:46 ` Linus Torvalds
2005-12-15 15:53 ` David Howells
2005-12-15 15:37 ` David Howells
2005-12-15 19:28 ` Andrew Morton
2005-12-15 20:18 ` Andrew Morton
2005-12-15 21:28 ` Steven Rostedt
2005-12-16 22:02 ` Thomas Gleixner
2005-12-16 10:45 ` David Howells
2005-12-13 9:55 ` Ingo Molnar
2005-12-13 0:30 ` Arnd Bergmann
2005-12-13 0:57 ` Daniel Walker
2005-12-13 3:23 ` Steven Rostedt
2005-12-13 2:57 ` Mark Lord
2005-12-13 3:17 ` Steven Rostedt
2005-12-13 9:06 ` Christoph Hellwig
2005-12-13 9:54 ` David Howells
2005-12-13 10:13 ` Ingo Molnar
2005-12-13 10:34 ` Ingo Molnar
2005-12-13 10:37 ` Ingo Molnar
2005-12-13 12:47 ` Oliver Neukum
2005-12-13 13:09 ` Alan Cox
2005-12-13 13:13 ` Matthew Wilcox
2005-12-13 14:04 ` Alan Cox
2005-12-13 13:24 ` Oliver Neukum
2005-12-14 1:00 ` Nick Piggin
2005-12-14 10:54 ` David Howells
2005-12-14 11:17 ` Nick Piggin
2005-12-14 11:46 ` David Howells
2005-12-14 21:23 ` Nick Piggin
2005-12-16 12:00 ` David Howells
2005-12-16 13:16 ` Nick Piggin
2005-12-16 15:53 ` David Howells
2005-12-16 23:41 ` Nick Piggin
2005-12-16 16:02 ` David Howells
2005-12-13 10:48 ` David Howells
2005-12-13 12:39 ` Matthew Wilcox
2005-12-13 10:54 ` Ingo Molnar
2005-12-13 11:23 ` David Howells
2005-12-13 11:24 ` David Howells
2005-12-13 13:45 ` Ingo Molnar
2005-12-13 11:34 ` David Howells
2005-12-13 13:05 ` Alan Cox
2005-12-13 13:15 ` Alan Cox
2005-12-13 23:21 ` Nikita Danilov
2005-12-13 13:32 ` David Howells
2005-12-13 14:00 ` Alan Cox
2005-12-13 14:35 ` Christopher Friesen
2005-12-13 14:44 ` Arjan van de Ven
2005-12-13 14:59 ` Christopher Friesen
2005-12-13 15:23 ` David Howells
2005-12-15 5:24 ` Miles Bader
2005-12-13 15:39 ` David Howells
2005-12-13 16:10 ` Alan Cox
2005-12-14 10:29 ` Arjan van de Ven
2005-12-14 11:03 ` Arjan van de Ven
2005-12-14 11:03 ` Alan Cox
2005-12-14 11:08 ` Arjan van de Ven
2005-12-14 11:24 ` Alan Cox
2005-12-14 11:35 ` Andrew Morton
2005-12-14 11:44 ` Arjan van de Ven
2005-12-14 11:52 ` Andi Kleen
2005-12-14 11:55 ` Arjan van de Ven
2005-12-14 11:57 ` David Howells
2005-12-14 12:19 ` Jakub Jelinek
2005-12-16 1:54 ` Nick Piggin
2005-12-16 11:02 ` David Howells
2005-12-16 13:01 ` Nick Piggin
2005-12-16 13:21 ` Russell King
2005-12-16 13:41 ` Nick Piggin
2005-12-16 13:46 ` Linh Dang
2005-12-16 14:31 ` Russell King
2005-12-16 15:24 ` Linh Dang
2005-12-16 15:35 ` Nick Piggin
2005-12-16 15:40 ` Kyle Moffett
2005-12-16 15:49 ` Linh Dang
2005-12-16 15:46 ` David Howells
2005-12-16 15:58 ` Russell King
2005-12-17 15:57 ` Nikita Danilov
2005-12-16 16:28 ` Linus Torvalds
2005-12-16 11:30 ` David Howells
2005-12-16 16:33 ` Linus Torvalds
2005-12-16 22:23 ` David S. Miller
2005-12-16 22:38 ` Linus Torvalds
2005-12-16 22:53 ` David S. Miller
2005-12-17 0:41 ` Jesse Barnes
2005-12-17 7:10 ` David S. Miller
2005-12-17 7:40 ` Linus Torvalds
2005-12-17 17:22 ` Jesse Barnes
2005-12-17 17:19 ` Jesse Barnes
2005-12-17 22:38 ` Richard Henderson
2005-12-17 23:05 ` David S. Miller
2005-12-14 12:17 ` Christoph Hellwig
2005-12-14 11:42 ` Arjan van de Ven
2005-12-14 8:31 ` Ingo Molnar
2005-12-13 20:04 ` Steven Rostedt
2005-12-13 21:03 ` David Howells
2005-12-15 13:58 linux
2005-12-15 16:15 ` Linus Torvalds
2005-12-15 16:52 ` Erik Mouw
2005-12-15 17:23 ` Dick Streefland
2005-12-16 12:17 ` Erik Mouw
2005-12-17 10:59 ` Sander
2005-12-17 14:14 ` Douglas McNaught
2005-12-17 15:09 ` Sander
2005-12-19 10:44 ` Erik Mouw
2005-12-15 19:02 ` Nikita Danilov
2005-12-15 19:09 ` linux
2005-12-15 19:52 ` Linus Torvalds
2005-12-16 1:33 ` linux
2005-12-15 21:18 ` Steven Rostedt
2005-12-15 20:52 ` Steven Rostedt
2005-12-15 17:45 Luck, Tony
2005-12-15 18:00 ` David Howells
2005-12-15 18:48 ` James Bottomley
2005-12-15 20:38 ` Jeff Dike
2005-12-15 23:45 ` Stephen Rothwell
2005-12-16 12:49 linux
2005-12-16 15:24 ` David Howells
2005-12-16 18:03 ` linux
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=20051212161944.3185a3f9.akpm@osdl.org \
--to=akpm@osdl.org \
--cc=arjan@infradead.org \
--cc=dhowells@redhat.com \
--cc=hch@infradead.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=matthew@wil.cx \
--cc=torvalds@osdl.org \
/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).