Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753542AbbHCNG7 (ORCPT ); Mon, 3 Aug 2015 09:06:59 -0400 Received: from casper.infradead.org ([85.118.1.10]:48425 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751791AbbHCNG6 (ORCPT ); Mon, 3 Aug 2015 09:06:58 -0400 Date: Mon, 3 Aug 2015 15:06:52 +0200 From: Peter Zijlstra To: Vineet Gupta Cc: lkml , "arc-linux-dev@synopsys.com" Subject: Re: [PATCH 5/6] ARCv2: spinlock/rwlock/atomics: Delayed retry of failed SCOND with exponential backoff Message-ID: <20150803130652.GO25159@twins.programming.kicks-ass.net> References: <1438596188-10875-1-git-send-email-vgupta@synopsys.com> <1438596188-10875-6-git-send-email-vgupta@synopsys.com> <20150803115059.GM25159@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1456 Lines: 33 On Mon, Aug 03, 2015 at 01:02:09PM +0000, Vineet Gupta wrote: > On Monday 03 August 2015 05:21 PM, Peter Zijlstra wrote: > > On Mon, Aug 03, 2015 at 03:33:07PM +0530, Vineet Gupta wrote: > > > > +#define SCOND_FAIL_RETRY_ASM \ > > + " bz 4f \n" \ > > + " ; --- scond fail delay --- \n" \ > > + " mov %[tmp], %[delay] \n" /* tmp = delay */ \ > > + "2: brne.d %[tmp], 0, 2b \n" /* while (tmp != 0) */ \ > > + " sub %[tmp], %[tmp], 1 \n" /* tmp-- */ \ > > + " asl %[delay], %[delay], 1 \n" /* delay *= 2 */ \ > > + " b 1b \n" /* start over */ \ > > + "4: ; --- success --- \n" \ > > > One more note, you might want a test to handle the case where delay *= 2 > overflows and results in a 0. > > > yeah ! > > - asl %[delay], %[delay], 1 > + asl.f %[delay], %[delay], 1 > + mov.z %[delay], 1 The other obvious option is: 0x80000000 :-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/