From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e33.co.us.ibm.com (e33.co.us.ibm.com [32.97.110.151]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id CE2612C00A2 for ; Tue, 28 Jan 2014 21:52:46 +1100 (EST) Received: from /spool/local by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 28 Jan 2014 03:52:43 -0700 Received: from b03cxnp07028.gho.boulder.ibm.com (b03cxnp07028.gho.boulder.ibm.com [9.17.130.15]) by d03dlp01.boulder.ibm.com (Postfix) with ESMTP id 25F071FF0021 for ; Tue, 28 Jan 2014 03:52:08 -0700 (MST) Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by b03cxnp07028.gho.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id s0SAqLbb9830896 for ; Tue, 28 Jan 2014 11:52:21 +0100 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s0SAqd5r008199 for ; Tue, 28 Jan 2014 03:52:41 -0700 Message-ID: <52E78B1F.80409@linux.vnet.ibm.com> Date: Tue, 28 Jan 2014 16:19:03 +0530 From: Preeti U Murthy MIME-Version: 1.0 To: daniel.lezcano@linaro.org, peterz@infradead.org, fweisbec@gmail.com, galak@kernel.crashing.org, paul.gortmaker@windriver.com, paulus@samba.org, mingo@kernel.org, mikey@neuling.org, shangw@linux.vnet.ibm.com, rafael.j.wysocki@intel.com, agraf@suse.de, benh@kernel.crashing.org, paulmck@linux.vnet.ibm.com, arnd@arndb.de, linux-pm@vger.kernel.org, rostedt@goodmis.org, michael@ellerman.id.au, john.stultz@linaro.org, anton@samba.org, tglx@linutronix.de, chenhui.zhao@freescale.com, deepthi@linux.vnet.ibm.com, r58472@freescale.com, geoff@infradead.org, linux-kernel@vger.kernel.org, srivatsa.bhat@linux.vnet.ibm.com, schwidefsky@de.ibm.com, svaidy@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH V2 0/2] time/cpuidle: Support in tick broadcast framework in absence of external clock device References: <20140124065501.17564.39363.stgit@preeti.in.ibm.com> In-Reply-To: <20140124065501.17564.39363.stgit@preeti.in.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Thomas, I realized that the below patch is also required for this patchset. This patch apart, I noticed that there is also one corner case which we will need to handle. The BROADCAST_ON notifications in periodic mode (oneshot mode is a nop). We will need to fail the BROADCAST_ON notification too in this case if the CPU in question is made the stand by CPU. Thanks Regards Preeti U Murthy --------------------------------------------------------------------------------- time/cpuidle:Handle failed call to BROADCAST_ENTER on archs with CPUIDLE_FLAG_TIMER_STOP set From: Preeti U Murthy Some archs set the CPUIDLE_FLAG_TIMER_STOP flag for idle states in which the local timers stop. The cpuidle_idle_call() currently handles such idle states by calling into the broadcast framework so as to wakeup CPUs at their next wakeup event. With the hrtimer mode of broadcast, the BROADCAST_ENTER call into the broadcast frameowork can fail for archs that do not have an external clock device to handle wakeups and the CPU in question has to thus be made the stand by CPU. This patch handles such cases by failing the call into cpuidle so that the arch can take some default action. The arch will certainly not enter a similar idle state because a failed cpuidle call will also implicitly indicate that the broadcast framework has not registered this CPU to be woken up. Hence we are safe if we fail the cpuidle call. In the process move the functions that trace idle statistics just before and after the entry and exit into idle states respectively. In other scenarios where the call to cpuidle fails, we end up not tracing idle entry and exit since a decision on an idle state could not be taken. Similarly when the call to broadcast framework fails, we skip tracing idle statistics because we are in no further position to take a decision on an alternative idle state to enter into. Signed-off-by: Preeti U Murthy --- drivers/cpuidle/cpuidle.c | 38 +++++++++++++++++++++++--------------- 1 file changed, 23 insertions(+), 15 deletions(-) diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index a55e68f..8f42033 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -117,15 +117,19 @@ int cpuidle_idle_call(void) { struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices); struct cpuidle_driver *drv; - int next_state, entered_state; - bool broadcast; + int next_state, entered_state, ret = 0; + bool broadcast = false; - if (off || !initialized) - return -ENODEV; + if (off || !initialized) { + ret = -ENODEV; + goto out; + } /* check if the device is ready */ - if (!dev || !dev->enabled) - return -EBUSY; + if (!dev || !dev->enabled) { + ret = -EBUSY; + goto out; + } drv = cpuidle_get_cpu_driver(dev); @@ -137,15 +141,18 @@ int cpuidle_idle_call(void) if (cpuidle_curr_governor->reflect) cpuidle_curr_governor->reflect(dev, next_state); local_irq_enable(); - return 0; + goto out; } - trace_cpu_idle_rcuidle(next_state, dev->cpu); - broadcast = !!(drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP); - if (broadcast) - clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu); + if (broadcast) { + ret = clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu); + if (ret) + goto out; + } + + trace_cpu_idle_rcuidle(next_state, dev->cpu); if (cpuidle_state_is_coupled(dev, drv, next_state)) entered_state = cpuidle_enter_state_coupled(dev, drv, @@ -153,16 +160,17 @@ int cpuidle_idle_call(void) else entered_state = cpuidle_enter_state(dev, drv, next_state); - if (broadcast) - clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu); - trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu); /* give the governor an opportunity to reflect on the outcome */ if (cpuidle_curr_governor->reflect) cpuidle_curr_governor->reflect(dev, entered_state); - return 0; +out: if (broadcast) + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu); + + + return ret; } /**