From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e39.co.us.ibm.com (e39.co.us.ibm.com [32.97.110.160]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id DDC6D1A1627 for ; Fri, 8 May 2015 17:36:58 +1000 (AEST) Received: from /spool/local by e39.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 8 May 2015 01:36:56 -0600 Received: from b01cxnp23033.gho.pok.ibm.com (b01cxnp23033.gho.pok.ibm.com [9.57.198.28]) by d01dlp03.pok.ibm.com (Postfix) with ESMTP id 6EBB3C90042 for ; Fri, 8 May 2015 03:28:02 -0400 (EDT) Received: from d01av05.pok.ibm.com (d01av05.pok.ibm.com [9.56.224.195]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id t487asM439321690 for ; Fri, 8 May 2015 07:36:54 GMT Received: from d01av05.pok.ibm.com (localhost [127.0.0.1]) by d01av05.pok.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id t487arBf007717 for ; Fri, 8 May 2015 03:36:54 -0400 Message-ID: <554C6780.5050306@linux.vnet.ibm.com> Date: Fri, 08 May 2015 13:06:32 +0530 From: Preeti U Murthy MIME-Version: 1.0 To: "Rafael J. Wysocki" Subject: Re: [PATCH V2] cpuidle: Handle tick_broadcast_enter() failure gracefully References: <20150507174355.25321.85885.stgit@preeti.in.ibm.com> <1562115.g1s3BW0dJA@vostro.rjw.lan> In-Reply-To: <1562115.g1s3BW0dJA@vostro.rjw.lan> Content-Type: text/plain; charset=UTF-8 Cc: rlippert@google.com, daniel.lezcano@linaro.org, linux-pm@vger.kernel.org, peterz@infradead.org, linus.walleij@linaro.org, rafael.j.wysocki@intel.com, linux-kernel@vger.kernel.org, mingo@redhat.com, sudeep.holla@arm.com, tglx@linutronix.de, linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 05/08/2015 02:20 AM, Rafael J. Wysocki wrote: > On Thursday, May 07, 2015 11:17:21 PM Preeti U Murthy wrote: >> When a CPU has to enter an idle state where tick stops, it makes a call >> to tick_broadcast_enter(). The call will fail if this CPU is the >> broadcast CPU. Today, under such a circumstance, the arch cpuidle code >> handles this CPU. This is not convincing because not only are we not >> aware what the arch cpuidle code does, but we also do not account for >> the idle state residency time and usage of such a CPU. >> >> This scenario can be handled better by simply asking the cpuidle >> governor to choose an idle state where in ticks do not stop. To >> accommodate this change move the setting of runqueue idle state from the >> core to the cpuidle driver, else the rq->idle_state will be set wrong. >> >> Signed-off-by: Preeti U Murthy >> --- >> Changes from V1: https://lkml.org/lkml/2015/5/7/24 >> Rebased on the latest linux-pm/bleeding-edge >> >> drivers/cpuidle/cpuidle.c | 21 +++++++++++++++++---- >> drivers/cpuidle/governors/ladder.c | 13 ++++++++++--- >> drivers/cpuidle/governors/menu.c | 6 +++++- >> include/linux/cpuidle.h | 6 +++--- >> include/linux/sched.h | 16 ++++++++++++++++ >> kernel/sched/core.c | 17 +++++++++++++++++ >> kernel/sched/fair.c | 2 +- >> kernel/sched/idle.c | 8 +------- >> kernel/sched/sched.h | 24 ------------------------ >> 9 files changed, 70 insertions(+), 43 deletions(-) >> >> diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c >> index 8c24f95..b7e86f4 100644 >> --- a/drivers/cpuidle/cpuidle.c >> +++ b/drivers/cpuidle/cpuidle.c >> @@ -21,6 +21,7 @@ >> #include >> #include >> #include >> +#include >> #include >> >> #include "cpuidle.h" >> @@ -168,10 +169,17 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, >> * CPU as a broadcast timer, this call may fail if it is not available. >> */ >> if (broadcast && tick_broadcast_enter()) { >> - default_idle_call(); >> - return -EBUSY; >> + index = cpuidle_select(drv, dev, !broadcast); > > No, you can't do that. > > This code path may be used by suspend-to-idle and that should not call > cpuidle_select(). > > What's needed here seems to be a fallback mechanism like "choose the > deepest state shallower than X and such that it won't stop the tick". > You don't really need to run a full governor for that. Agreed. Makes the patch a lot simpler as well. I have sent out V3 doing this. Thank you Regards Preeti U Murthy > >