Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753203AbbHCLvH (ORCPT ); Mon, 3 Aug 2015 07:51:07 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:41495 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752403AbbHCLvG (ORCPT ); Mon, 3 Aug 2015 07:51:06 -0400 Date: Mon, 3 Aug 2015 13:50:59 +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: <20150803115059.GM25159@twins.programming.kicks-ass.net> References: <1438596188-10875-1-git-send-email-vgupta@synopsys.com> <1438596188-10875-6-git-send-email-vgupta@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1438596188-10875-6-git-send-email-vgupta@synopsys.com> 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: 805 Lines: 18 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. -- 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/