| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Thu, 06 Feb 2014 13:50:50 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc: rafael.j.wysocki@...el.com, linux-pm@...r.kernel.org,
peterz@...radead.org, fweisbec@...il.com,
daniel.lezcano@...aro.org, linux-kernel@...r.kernel.org,
paulus@...ba.org, benh@...nel.crashing.org, tglx@...utronix.de,
linuxppc-dev@...ts.ozlabs.org, mingo@...nel.org,
deepthi@...ux.vnet.ibm.com, paulmck@...ux.vnet.ibm.com,
svaidy@...ux.vnet.ibm.com, srivatsa.bhat@...ux.vnet.ibm.com
Subject: Re: [PATCH V3 3/3] time/cpuidle:Handle failed call to BROADCAST_ENTER on archs with CPUIDLE_FLAG_TIMER_STOP set
On Thursday, February 06, 2014 11:20:37 AM Preeti U Murthy wrote:
> 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 <preeti@...ux.vnet.ibm.com>
The cpuidle changes in this patch look reasonable to me, but I guess you'd
like it to go in via tip along with the rest of the series, so
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>
> 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;
> }
>
> /**
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pm" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists