From mboxrd@z Thu Jan 1 00:00:00 1970 From: peterz@infradead.org (Peter Zijlstra) Date: Tue, 17 Nov 2015 12:23:43 +0100 Subject: [PATCH v2 18/19] ARC: [plat-eznps] replace sync with proper cpu barrier In-Reply-To: <564B0BB1.8080709@synopsys.com> References: <1446297327-16298-1-git-send-email-noamc@ezchip.com> <1446893557-29748-19-git-send-email-noamc@ezchip.com> <564B0BB1.8080709@synopsys.com> List-ID: Message-ID: <20151117112343.GW3816@twins.programming.kicks-ass.net> To: linux-snps-arc@lists.infradead.org On Tue, Nov 17, 2015@04:42:49PM +0530, Vineet Gupta wrote: > On Saturday 07 November 2015 04:22 PM, Noam Camus wrote: > > From: Tal Zilcer > > > > In SMT system like we have the generic "sync" is not working with > > HW threads. The replacement is "schd.rw" instruction that is served > > as cpu barrier for HW threads. > > As discussed in v2 of this patch, SYNC or some such in __switch_to is completely > superfluous. We don't need this patch, you may instead wanna submit a patch which > removes the sync. Also please do that in assembler version of this file as well ! Do test it though; as is ARC-SMP seems to have a _lot_ of superfluous barriers many of which have no explanation yet (I'm thinking of those extra smp_mb()s in the lock primitives).