From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <439FFF63.6020105@yahoo.com.au> Date: Wed, 14 Dec 2005 22:17:55 +1100 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [PATCH 1/19] MUTEX: Introduce simple mutex implementation References: <439F6EAB.6030903@yahoo.com.au> <439E122E.3080902@yahoo.com.au> <22479.1134467689@warthog.cambridge.redhat.com> <13613.1134557656@warthog.cambridge.redhat.com> In-Reply-To: <13613.1134557656@warthog.cambridge.redhat.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit To: David Howells Cc: torvalds@osdl.org, akpm@osdl.org, hch@infradead.org, arjan@infradead.org, matthew@wil.cx, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org List-ID: David Howells wrote: > Nick Piggin wrote: > > >>atomic_cmpxchg should be available on all platforms. > > > Two points: > > (1) If it's using spinlocks, then it's pointless to use atomic_cmpxchg. > Why? > (2) atomic_t is a 32-bit type, and on a 64-bit platform I will want a 64-bit > type so that I can stick the owner address in there (I've got a second > variant not yet released). > I'm sure you could use a seperate field as it would be a debug option, right? But atomic longs are coming along and it is probably feasable to do 64-bit atomic_cmpxchg on all 64-bit word architectures if you really needed that. Send instant messages to your online friends http://au.messenger.yahoo.com