Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751748Ab3HAAQy (ORCPT ); Wed, 31 Jul 2013 20:16:54 -0400 Received: from smtp.codeaurora.org ([198.145.11.231]:49546 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750856Ab3HAAQw (ORCPT ); Wed, 31 Jul 2013 20:16:52 -0400 Message-ID: <51F9A8F1.9020704@codeaurora.org> Date: Wed, 31 Jul 2013 17:16:49 -0700 From: Stephen Boyd User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:17.0) Gecko/20130620 Thunderbird/17.0.7 MIME-Version: 1.0 To: Timur Tabi CC: Arpit Goel , linux@arm.linux.org.uk, takata@linux-m32r.org, philb@gnu.org, Geert Uytterhoeven , schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, linux390@de.ibm.com, David Miller , Rob Herring , Arnd Bergmann , Stephen Warren , john.stultz@linaro.org, jesper.nilsson@axis.com, gregkh@linuxfoundation.org, sam@ravnborg.org, "linux-arm-kernel@lists.infradead.org" , lkml , linux-m32r@ml.linux-m32r.org, linux-m32r-ja@ml.linux-m32r.org, linux-m68k@vger.kernel.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, mattw@codeaurora.org Subject: Re: [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architecture independent macro References: <1375187900-17582-1-git-send-email-B44344@freescale.com> <1375187900-17582-3-git-send-email-B44344@freescale.com> <20130731071630.GI8868@codeaurora.org> <51F9A5FE.8030608@codeaurora.org> <51F9A80E.5010307@tabi.org> In-Reply-To: <51F9A80E.5010307@tabi.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1245 Lines: 29 On 07/31/13 17:13, Timur Tabi wrote: > On 07/31/2013 07:04 PM, Stephen Boyd wrote: >> If it yields why are we using udelay? Why not usleep_range()? It would >> be useful to have a variant that worked in interrupt context and it >> looked like that was almost possible. > I've never heard of usleep_range() before, so I don't know if it > applies. Apparently, udelay() includes its own call to cpu_relax(). Is > it possible that cpu_relax() is a "lightweight" yield, compared to sleeping? cpu_relax() is usually just a compiler barrier or an instruction hint to the cpu that it should cool down because we're spinning in a tight loop. It certainly shouldn't be calling into the scheduler. > > FYI, you might want to look at the code reviews for spin_event_timeout() > on the linuxppc-dev mailing list, back in March 2009. > Sure. Any pointers? Otherwise I'll go digging around the archives. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- 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/