From: Pavel Machek <pavel@ucw.cz>
To: Andrew Morton <akpm@osdl.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Greg Kroah-Hartman <gregkh@suse.de>,
Christoph Hellwig <hch@infradead.org>,
ltt-dev@shafik.org, systemtap@sources.redhat.com,
Douglas Niehaus <niehaus@eecs.ku.edu>,
"Martin J. Bligh" <mbligh@mbligh.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] local_t : Documentation
Date: Tue, 9 Jan 2007 23:38:26 +0100 [thread overview]
Message-ID: <20070109223826.GA6555@elf.ucw.cz> (raw)
In-Reply-To: <20070109130110.8934c29f.akpm@osdl.org>
On Tue 2007-01-09 13:01:10, Andrew Morton wrote:
> On Mon, 8 Jan 2007 22:14:46 -0500
> Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
>
> > +* How to use local atomic operations
> > +
> > +#include <linux/percpu.h>
> > +#include <asm/local.h>
> > +
> > +static DEFINE_PER_CPU(local_t, counters) = LOCAL_INIT(0);
> > +
> > +
> > +* Counting
> > +
> > +In preemptible context, use get_cpu_var() and put_cpu_var() around local atomic
> > +operations : it makes sure that preemption is disabled around write access to
> > +the per cpu variable. For instance :
> > +
> > + local_inc(&get_cpu_var(counters));
> > + put_cpu_var(counters);
>
> Confused. The whole point behind local_t is that we can do
> atomic-wrt-interrupts inc and dec on them.
Could we get this short of two line description into the Doc/ file? It
talks about how to implement them, mentions LOCK prefixes unlikely to
be present on non-i386, but does not tell me what they guarantee...
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
next prev parent reply other threads:[~2007-01-09 22:38 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-21 0:15 [PATCH 0/10] local_t : adding and standardising atomic primitives Mathieu Desnoyers
2006-12-21 0:20 ` [PATCH 1/10] local_t : architecture agnostic Mathieu Desnoyers
2006-12-21 0:21 ` [PATCH 2/10] local_t : alpha Mathieu Desnoyers
2006-12-21 0:22 ` [PATCH 3/10] local_t : i386 Mathieu Desnoyers
2006-12-21 19:44 ` [Ltt-dev] [PATCH 3/10] local_t : i386, local_add_return fix Mathieu Desnoyers
2006-12-21 0:23 ` [PATCH 4/10] local_t : ia64 Mathieu Desnoyers
2006-12-21 0:25 ` [PATCH 5/10] " Mathieu Desnoyers
2006-12-21 14:04 ` [Ltt-dev] [PATCH 5/10] local_t : MIPS Mathieu Desnoyers
2006-12-21 0:25 ` [PATCH 6/10] local_t : parisc Mathieu Desnoyers
2006-12-21 0:27 ` [PATCH 7/10] local_t : powerpc Mathieu Desnoyers
2006-12-21 3:34 ` [Ltt-dev] " Mathieu Desnoyers
2007-01-24 9:08 ` Paul Mackerras
2007-01-24 10:43 ` Gabriel Paubert
2007-01-24 17:00 ` Mathieu Desnoyers
2006-12-21 0:27 ` [PATCH 8/10] local_t : s390 Mathieu Desnoyers
2006-12-21 0:28 ` [PATCH 9/10] local_t : sparc64 Mathieu Desnoyers
2006-12-21 0:29 ` [PATCH 10/10] local_t : x86_64 Mathieu Desnoyers
2006-12-21 19:46 ` [Ltt-dev] [PATCH 10/10] local_t : x86_64 : local_add_return Mathieu Desnoyers
2006-12-23 9:33 ` [PATCH 0/10] local_t : adding and standardising atomic primitives Pavel Machek
2007-01-09 3:14 ` [PATCH] local_t : Documentation Mathieu Desnoyers
2007-01-09 21:01 ` Andrew Morton
2007-01-09 22:06 ` Mathieu Desnoyers
2007-01-09 22:11 ` Andrew Morton
2007-01-09 22:38 ` Pavel Machek [this message]
2007-01-09 22:41 ` Pavel Machek
2007-01-09 23:21 ` [PATCH] local_t : Documentation - update Mathieu Desnoyers
2007-01-09 23:45 ` Pavel Machek
2007-01-10 0:39 ` Mathieu Desnoyers
2007-01-10 1:06 ` [Ltt-dev] " Mathieu Desnoyers
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