On 15.10.2015 17:23, Pavel Emelyanov wrote:
> On 10/15/2015 05:21 PM, Kirill Tkhai wrote:
>>
>>
>> On 15.10.2015 14:15, Pavel Emelyanov wrote:
>>>
>>>> @@ -130,6 +131,34 @@ struct ve_struct {
>>>> #endif
>>>> };
>>>>
>>>> +static inline struct ve_struct *get_exec_env(void)
>>>> +{
>>>> + struct ve_struct *ve;
>>>> +
>>>> + if (++current->ve_attach_lock_depth > 1)
>>>> + return current->task_ve;
>>>> +
>>>> + rcu_read_lock();
>>>> +again:
>>>> + ve = current->task_ve;
>>>> + read_lock(&ve->attach_lock);
>>>> + if (unlikely(current->task_ve != ve)) {
>>>> + read_unlock(&ve->attach_lock);
>>>> + goto again;
>>>
>>> Please, no. 3.10 kernel has task_work-s, ask the task you want to
>>> attach to ve to execute the work by moving itself into it and keep
>>> this small routine small and simple.
>>
>> cgroup_attach_task() is called under cgroup_mutex and threadgroup_lock(),
>> so we can't wait attaching task till it complete the task work (it may
>> execute any code; to be locking cgroup_mutex, for example).
>
> I see.
>
>> Should we give a possibility (an interface) for userspace to get it know,
>> the task's finished ve changing?
>
> No. What are the places where get_exec_env() is still required?
Ok.
We use it from time to time
$ git grep get_exec_env | grep -v ve_is_super | wc -l
71
>>
>>>> + }
>>>> + rcu_read_unlock();
>>>> +
>>>> + return ve;
>>>> +}
>>>> +
>>>
>> .
>>
>
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