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Message-ID: <5541A5DF.4080700@linux.vnet.ibm.com>
Date: Thu, 30 Apr 2015 09:17:43 +0530
From: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Sudeep Holla <sudeep.holla@....com>,
Peter Zijlstra <peterz@...radead.org>,
Linus Walleij <linus.walleij@...aro.org>,
Daniel Lezcano <daniel.lezcano@...aro.org>
CC: "Rafael J. Wysocki" <rafael@...nel.org>,
Linux PM list <linux-pm@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH][Fix] cpuidle: Run tick_broadcast_exit() with disabled
interrupts
On 04/29/2015 07:37 PM, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Commit 335f49196fd6 (sched/idle: Use explicit broadcast oneshot
> control function) replaced clockevents_notify() invocations in
> cpuidle_idle_call() with direct calls to tick_broadcast_enter()
> and tick_broadcast_exit(), but it overlooked the fact that
> interrupts were already enabled before calling the latter which
> led to functional breakage on systems using idle states with the
> CPUIDLE_FLAG_TIMER_STOP flag set.
>
> Fix that by moving the invocations of tick_broadcast_enter()
> and tick_broadcast_exit() down into cpuidle_enter_state() where
> interrupts are still disabled when tick_broadcast_exit() is
> called. Also ensure that interrupts will be disabled before
> running tick_broadcast_exit() even if they have been enabled by
> the idle state's ->enter callback. Trigger a WARN_ON_ONCE() in
> that case, as we generally don't want that to happen for states
> with CPUIDLE_FLAG_TIMER_STOP set.
>
> Fixes: 335f49196fd6 (sched/idle: Use explicit broadcast oneshot control function)
> Reported-and-tested-by: Linus Walleij <linus.walleij@...aro.org>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Reported-and-tested-by: Sudeep Holla <sudeep.holla@....com>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>
> Thanks for the testing and ACKs, here it goes again with all tags and
> a changelog.
>
> If anything is missing/incorrect, please let me know ASAP as I'm going to
> push this to Linus in a couple of days.
>
> ---
> drivers/cpuidle/cpuidle.c | 16 ++++++++++++++++
> kernel/sched/idle.c | 16 ++--------------
> 2 files changed, 18 insertions(+), 14 deletions(-)
>
> Index: linux-pm/kernel/sched/idle.c
> ===================================================================
> --- linux-pm.orig/kernel/sched/idle.c
> +++ linux-pm/kernel/sched/idle.c
> @@ -81,7 +81,6 @@ static void cpuidle_idle_call(void)
> struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
> struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
> int next_state, entered_state;
> - unsigned int broadcast;
> bool reflect;
>
> /*
> @@ -150,17 +149,6 @@ static void cpuidle_idle_call(void)
> goto exit_idle;
> }
>
> - broadcast = drv->states[next_state].flags & CPUIDLE_FLAG_TIMER_STOP;
> -
> - /*
> - * Tell the time framework to switch to a broadcast timer
> - * because our local timer will be shutdown. If a local timer
> - * is used from another cpu as a broadcast timer, this call may
> - * fail if it is not available
> - */
> - if (broadcast && tick_broadcast_enter())
> - goto use_default;
> -
> /* Take note of the planned idle state. */
> idle_set_state(this_rq(), &drv->states[next_state]);
>
> @@ -174,8 +162,8 @@ static void cpuidle_idle_call(void)
> /* The cpu is no longer idle or about to enter idle. */
> idle_set_state(this_rq(), NULL);
>
> - if (broadcast)
> - tick_broadcast_exit();
> + if (entered_state == -EBUSY)
> + goto use_default;
>
> /*
> * Give the governor an opportunity to reflect on the outcome
> Index: linux-pm/drivers/cpuidle/cpuidle.c
> ===================================================================
> --- linux-pm.orig/drivers/cpuidle/cpuidle.c
> +++ linux-pm/drivers/cpuidle/cpuidle.c
> @@ -158,9 +158,18 @@ int cpuidle_enter_state(struct cpuidle_d
> int entered_state;
>
> struct cpuidle_state *target_state = &drv->states[index];
> + bool broadcast = !!(target_state->flags & CPUIDLE_FLAG_TIMER_STOP);
> ktime_t time_start, time_end;
> s64 diff;
>
> + /*
> + * Tell the time framework to switch to a broadcast timer because our
> + * local timer will be shut down. If a local timer is used from another
> + * CPU as a broadcast timer, this call may fail if it is not available.
> + */
> + if (broadcast && tick_broadcast_enter())
> + return -EBUSY;
> +
> trace_cpu_idle_rcuidle(index, dev->cpu);
> time_start = ktime_get();
>
> @@ -169,6 +178,13 @@ int cpuidle_enter_state(struct cpuidle_d
> time_end = ktime_get();
> trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);
>
> + if (broadcast) {
> + if (WARN_ON_ONCE(!irqs_disabled()))
> + local_irq_disable();
> +
> + tick_broadcast_exit();
> + }
> +
> if (!cpuidle_state_is_coupled(dev, drv, entered_state))
> local_irq_enable();
>
Reviewed-by: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
>
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