From: David Howells <dhowells@redhat.com>
To: Christoph Lameter <clameter@sgi.com>
Cc: David Howells <dhowells@redhat.com>,
Ralf Baechle <ralf@linux-mips.org>,
Nick Piggin <nickpiggin@yahoo.com.au>,
Arjan van de Ven <arjan@infradead.org>,
Dong Feng <middle.fengdong@gmail.com>,
ak@suse.de, Paul Mackerras <paulus@samba.org>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: Why Semaphore Hardware-Dependent?
Date: Tue, 29 Aug 2006 17:57:36 +0100 [thread overview]
Message-ID: <21013.1156870656@warthog.cambridge.redhat.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0608290926230.18503@schroedinger.engr.sgi.com>
Christoph Lameter <clameter@sgi.com> wrote:
> > Some of these have LL/SC or equivalent instead, but ARM5 and before, FRV,
> > M68K before 68020 to name but a few.
>
> This is all pretty ancient hardware, right? And they are mostly single
> processor so no need to worry about concurrency. Just disable interrupts.
No, they're not all ancient h/w, and "just disabling interrupts" can be really
expensive.
> > And anything that implements CMPXCHG with spinlocks is a really bad
> > candidate for CMPXCHG-based rwsems.
>
> Those will optimize out if it is a single processor configuration.
Not necessarily. Consider preemption.
David
next prev parent reply other threads:[~2006-08-29 16:57 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <a2ebde260608271222x2b51693fnaa600965fcfaa6d2@mail.gmail.com>
[not found] ` <1156750249.3034.155.camel@laptopd505.fenrus.org>
2006-08-29 1:18 ` Why Semaphore Hardware-Dependent? Nick Piggin
2006-08-29 6:07 ` Andi Kleen
2006-09-13 17:54 ` Nick Piggin
2006-08-29 10:05 ` David Howells
2006-08-29 10:56 ` Andi Kleen
2006-08-29 17:40 ` Andrew Morton
2006-08-29 19:10 ` Benjamin LaHaise
2006-08-29 15:56 ` Christoph Lameter
2006-08-29 16:20 ` Ralf Baechle
2006-08-29 16:25 ` David Howells
2006-08-29 16:28 ` Christoph Lameter
2006-08-29 16:57 ` David Howells [this message]
2006-08-29 16:53 ` Ralf Baechle
2006-08-29 16:58 ` Geert Uytterhoeven
2006-08-29 17:22 ` Andi Kleen
2006-08-29 17:36 ` Christoph Lameter
2006-08-29 18:18 ` Andi Kleen
2006-08-29 18:30 ` David Howells
2006-08-29 18:33 ` Andi Kleen
2006-08-29 18:56 ` David Howells
2006-08-29 18:41 ` Christoph Lameter
2006-09-13 18:04 ` Nick Piggin
2006-09-13 18:07 ` Christoph Lameter
2006-09-13 18:13 ` Nick Piggin
2006-09-13 18:16 ` Christoph Lameter
2006-09-13 18:50 ` David Howells
2006-09-13 19:25 ` Nick Piggin
2006-09-14 11:41 ` David Howells
2006-09-14 15:27 ` Nick Piggin
2006-09-14 15:38 ` Nick Piggin
2006-09-15 8:59 ` David Howells
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