X-Recipient: archive-cygwin@delorie.com X-Spam-Check-By: sourceware.org Date: Wed, 10 Mar 2010 10:12:52 -0500 From: Christopher Faylor To: cygwin@cygwin.com Subject: Re: Cygwin 1.7: Concurrency Issue with Shared State Initialization Message-ID: <20100310151252.GC19509@ednor.casa.cgf.cx> Reply-To: cygwin@cygwin.com Mail-Followup-To: cygwin@cygwin.com References: <20100310095929.GY6505@calimero.vinschen.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100310095929.GY6505@calimero.vinschen.de> User-Agent: Mutt/1.5.20 (2009-06-14) Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Delivered-To: mailing list cygwin@cygwin.com On Wed, Mar 10, 2010 at 10:59:29AM +0100, Corinna Vinschen wrote: >On Mar 10 10:55, Schmidt, Oliver wrote: >> Hi Corrina, >> >> Thanks for your involvement :-) >> >> >> [...] a spinlock [...] With >> >> InterlockedCompareExchange() and Sleep() it should be quite simple to >> >> create one that's very efficient in the usual scenario. >> >> > Does the below patch fix this for you? >> >> I'll test the snapshot asap! >> >> [...] >> + LONG init = InterlockedCompareExchange (&installation_root_init, 1L, 0L); >> [...] >> + low_priority_sleep (0); >> [...] >> >> I see we were thinking along the same lines ;-) > >The final patch is from cgf. It's probably more performant since it >drops the requirement for an additional spinlock. The snapshot contains try #3 on getting the locking right. I had to scrap my approach after Corinna politely reminded me that I had done something stupid in the prior snapshot. But, the spinlock approach was nothing new. We use that technique in several places in Cygwin. cgf -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple