From mboxrd@z Thu Jan 1 00:00:00 1970 From: Preeti U Murthy Subject: Re: [PATCH v2 1/6] idle: move the cpuidle entry point to the generic idle loop Date: Thu, 30 Jan 2014 11:20:17 +0530 Message-ID: <52E9E819.4040002@linux.vnet.ibm.com> References: <1391017513-12995-1-git-send-email-nicolas.pitre@linaro.org> <1391017513-12995-2-git-send-email-nicolas.pitre@linaro.org> <52E9C946.50704@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from e8.ny.us.ibm.com ([32.97.182.138]:36453 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751097AbaA3Fxy (ORCPT ); Thu, 30 Jan 2014 00:53:54 -0500 Received: from /spool/local by e8.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 30 Jan 2014 00:53:54 -0500 In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Nicolas Pitre Cc: Olof Johansson , Russell King , Benjamin Herrenschmidt , Paul Mundt , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , "Rafael J. Wysocki" , Daniel Lezcano , linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org, linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org Hi Nicolas, On 01/30/2014 10:58 AM, Nicolas Pitre wrote: > On Thu, 30 Jan 2014, Preeti U Murthy wrote: > >> Hi Nicolas, >> >> On 01/30/2014 02:01 AM, Nicolas Pitre wrote: >>> On Wed, 29 Jan 2014, Nicolas Pitre wrote: >>> >>>> In order to integrate cpuidle with the scheduler, we must have a better >>>> proximity in the core code with what cpuidle is doing and not delegate >>>> such interaction to arch code. >>>> >>>> Architectures implementing arch_cpu_idle() should simply enter >>>> a cheap idle mode in the absence of a proper cpuidle driver. >>>> >>>> Signed-off-by: Nicolas Pitre >>>> Acked-by: Daniel Lezcano >>> >>> As mentioned in my reply to Olof's comment on patch #5/6, here's a new >>> version of this patch adding the safety local_irq_enable() to the core >>> code. >>> >>> ----- >8 >>> >>> From: Nicolas Pitre >>> Subject: idle: move the cpuidle entry point to the generic idle loop >>> >>> In order to integrate cpuidle with the scheduler, we must have a better >>> proximity in the core code with what cpuidle is doing and not delegate >>> such interaction to arch code. >>> >>> Architectures implementing arch_cpu_idle() should simply enter >>> a cheap idle mode in the absence of a proper cpuidle driver. >>> >>> In both cases i.e. whether it is a cpuidle driver or the default >>> arch_cpu_idle(), the calling convention expects IRQs to be disabled >>> on entry and enabled on exit. There is a warning in place already but >>> let's add a forced IRQ enable here as well. This will allow for >>> removing the forced IRQ enable some implementations do locally and >> >> Why would this patch allow for removing the forced IRQ enable that are >> being done on some archs in arch_cpu_idle()? Isn't this patch expecting >> the default arch_cpu_idle() to have re-enabled the interrupts after >> exiting from the default idle state? Its supposed to only catch faulty >> cpuidle drivers that haven't enabled IRQs on exit from idle state but >> are expected to have done so, isn't it? > > Exact. However x86 currently does this: > > if (cpuidle_idle_call()) > x86_idle(); > else > local_irq_enable(); > > So whenever cpuidle_idle_call() is successful then IRQs are > unconditionally enabled whether or not the underlying cpuidle driver has > properly done it or not. And the reason is that some of the x86 cpuidle > do fail to enable IRQs before returning. > > So the idea is to get rid of this unconditional IRQ enabling and let the > core issue a warning instead (as well as enabling IRQs to allow the > system to run). Oh ok, thank you for clarifying this:) Regards Preeti U Murthy > > > Nicolas >