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SubjectRe: [PATCH] cpuidle: coupled: fix sleeping while atomic in cpu notifier
Date
On Wednesday, July 25, 2012, Colin Cross wrote:
> The cpu hotplug notifier gets called in both atomic and non-atomic
> contexts, it is not always safe to lock a mutex. Filter out all events
> except the six necessary ones, which are all sleepable, before taking
> the mutex.

I wonder what mutual exclusion mechanis we rely on when the mutex is not taken?

Rafael


> Signed-off-by: Colin Cross <ccross@android.com>
> ---
> drivers/cpuidle/coupled.c | 12 ++++++++++++
> 1 files changed, 12 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/cpuidle/coupled.c b/drivers/cpuidle/coupled.c
> index 2c9bf26..c24dda0 100644
> --- a/drivers/cpuidle/coupled.c
> +++ b/drivers/cpuidle/coupled.c
> @@ -678,6 +678,18 @@ static int cpuidle_coupled_cpu_notify(struct notifier_block *nb,
> int cpu = (unsigned long)hcpu;
> struct cpuidle_device *dev;
>
> + switch (action & ~CPU_TASKS_FROZEN) {
> + case CPU_UP_PREPARE:
> + case CPU_DOWN_PREPARE:
> + case CPU_ONLINE:
> + case CPU_DEAD:
> + case CPU_UP_CANCELED:
> + case CPU_DOWN_FAILED:
> + break;
> + default:
> + return NOTIFY_OK;
> + }
> +
> mutex_lock(&cpuidle_lock);
>
> dev = per_cpu(cpuidle_devices, cpu);
>



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