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: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-27 19:22 Why Semaphore Hardware-Dependent? Dong Feng
2006-08-27 20:52 ` Andi Kleen
2006-08-27 21:05 ` Christoph Lameter
2006-08-27 21:39 ` Andi Kleen
2006-08-27 22:14 ` Christoph Lameter
2006-08-28 0:18 ` Paul Mackerras
2006-08-28 5:14 ` Chris Wedgwood
2006-08-28 5:21 ` Christoph Lameter
2006-08-28 5:56 ` Jan Engelhardt
2006-08-28 12:35 ` linux-os (Dick Johnson)
2006-08-28 7:23 ` Andi Kleen
2006-08-29 1:00 ` Paul Mackerras
2006-08-28 7:30 ` Arjan van de Ven
2006-08-29 1:18 ` 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
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=21013.1156870656@warthog.cambridge.redhat.com \
--to=dhowells@redhat.com \
--cc=ak@suse.de \
--cc=arjan@infradead.org \
--cc=clameter@sgi.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=middle.fengdong@gmail.com \
--cc=nickpiggin@yahoo.com.au \
--cc=paulus@samba.org \
--cc=ralf@linux-mips.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.