Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753342AbbHCLn6 (ORCPT ); Mon, 3 Aug 2015 07:43:58 -0400 Received: from casper.infradead.org ([85.118.1.10]:47906 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753248AbbHCLn5 (ORCPT ); Mon, 3 Aug 2015 07:43:57 -0400 Date: Mon, 3 Aug 2015 13:43:52 +0200 From: Peter Zijlstra To: Vineet Gupta Cc: lkml , arc-linux-dev@synopsys.com Subject: Re: [PATCH 6/6] ARCv2: spinlock/rwlock: Reset retry delay when starting a new spin-wait cycle Message-ID: <20150803114352.GL25159@twins.programming.kicks-ass.net> References: <1438596188-10875-1-git-send-email-vgupta@synopsys.com> <1438596188-10875-7-git-send-email-vgupta@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1438596188-10875-7-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: 802 Lines: 17 On Mon, Aug 03, 2015 at 03:33:08PM +0530, Vineet Gupta wrote: > A spin lock could be available momentarily, but the SCOND to actually > acquire it might still fail due to concurrent update from other core(s). > To elide hardware lock, the sequence is retried after a "delay" which is > increased expoenntially to get a nice backoff behaviour. > > However, this could cause the delay counter to get to a high value. Thus > when the next spin cycle restarts, reset the counter back to starting > value of 1. Cute.. fwiw, did you look at what Sparc64 does? -- 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/