On 20 May 2013 14:26, Michael Wang <wangyun@xxxxxxxxxxxxxxxxxx> wrote:
> On 05/20/2013 03:25 PM, Michael Wang wrote:
>> Yeah, that's right, I guess the issue is, although the policy->cpus is
>> correct at a given time, after get cpu from it, it's possible to be
>> changed, unless we disabled preempt or irq, or hotplug before we use it...
>>
>> Like such issue cases:
>> get x from policy->cpus
>> DOWN notifier
>> change policy->cpus
>> do offline x
>> send ipi to x
>>
>> Will that happen?
Sorry I am not sure. :(
I can see mutex being used in cpufreq_governor.c which should take care
of race conditions...
> May be we could do some test to confirm it?
>
> diff --git a/drivers/cpufreq/cpufreq_governor.c
> b/drivers/cpufreq/cpufreq_governor.c
> index 443442d..449be88 100644
> --- a/drivers/cpufreq/cpufreq_governor.c
> +++ b/drivers/cpufreq/cpufreq_governor.c
> @@ -26,6 +26,7 @@
> #include <linux/tick.h>
> #include <linux/types.h>
> #include <linux/workqueue.h>
> +#include <linux/cpu.h>
>
> #include "cpufreq_governor.h"
>
> @@ -180,8 +181,10 @@ void gov_queue_work(struct dbs_data *dbs_data,
> struct cpufreq_policy *policy,
> if (!all_cpus) {
> __gov_queue_work(smp_processor_id(), dbs_data, delay);
> } else {
> + get_online_cpus();
> for_each_cpu(i, policy->cpus)
> __gov_queue_work(i, dbs_data, delay);
> + put_online_cpus();
> }
> }
> EXPORT_SYMBOL_GPL(gov_queue_work);
>
> This is supposed to make WARN disappear, if it works, then BINGO :)
Let people test it and then we can talk :)
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