From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Date: Sat, 01 Apr 2006 02:56:55 +0000 Subject: Re: Synchronizing Bit operations V2 Message-Id: <442DEBF7.1090806@yahoo.com.au> List-Id: References: <442C7B51.1060203@yahoo.com.au> <442CAC11.4070803@yahoo.com.au> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Christoph Lameter Cc: Zoltan Menyhart , "Boehm, Hans" , "Grundler, Grant G" , "Chen, Kenneth W" , akpm@osdl.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org Christoph Lameter wrote: > On Fri, 31 Mar 2006, Nick Piggin wrote: >>You acknowledge that you have to fix ia64 to match current semantics >>first, right? > > > Right. I believe I have done so by making both smb_mb_* full barriers. All bitop and atomic test_and_set, inc_return, etc etc (ie. everything that modifies the operand and returns something) needs to be a full barrier before and after too. >>Now people seem to be worried about the performance impact that will >>have, so I simply suggest that adding two or three new macros for the >>important cases to give you a 90% solution. > > > We could transition some key locations of core code to use _mode bitops > if there are performance problems. > > >>I think Documentation/atomic_ops.txt isn't bad. smp_mb__* really >>is a smp_mb, which can be optimised sometimes. > > > Ok. Then we are on the same page and the solution I presented may be > acceptable. I have a new rev here that changes the naming a bit but I > think we are okay right? Not sure, to be honest. I think it is probably something which needs input from all the other arch people, and Linus, if you intend to use it to introduce new types of barriers. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com