Philippe Gerum wrote:
>> does your patch fix also the situation when the task is suspended via
>> T_SUSP flag from rt_task_shadow (and calls which start tasks, for that
>> matter) ?
>>
>
> No, that is a different case; this patches only ensures that rt_task_suspend()
> shall be automatically restarted upon signal receipt when called for the
> running
> task.
>
I thought that the user space call to rt_task_suspend should return
-EINTR. So where is the automatic restarting ?
>> Then I've applied your patch to task.c in my kernel tree, recompiled the
>> kernel, and my task is still getting resumed too early, returning 0.
>> Even when I use rt_task_suspend. Could this be caused by something else ?
>>
>
> No, it does happen due to the shadowed task receiving SIGALRM. If you don't
> want
> this to happen, just block the signals before calling rt_task_shadow(). There
> is
> no other way, we may not restart the shadow mapping request upon signal
> receipt
> anyway.
>
OK, lets forget about rt_task_shadow, I agree the repetition/EINTR
semantics would be non-intuitive there. But even rt_task_suspend is
interrupted by signal, returning 0, even after applying the patch. I
don't quite understand why.
Tomas
>
>> Thanks,
>> Tomas
>>
>>
>>
>> Philippe Gerum wrote:
>>
>>> Philippe Gerum wrote:
>>>
>>>
>>>> Tomas Kalibera wrote:
>>>>
>>>>
>>>>> Hi,
>>>>>
>>>>> what can, besides an explicit call, resume a suspended task ? I
>>>>> created and started a child task, then shadowed the current thread
>>>>> with T_SUSP flag. The child was supposed to call rt_task_resume to
>>>>> wake-up the parent and let it terminate the process, but, the parent
>>>>> was resumed before this call. The call to rt_task_suspend in parent
>>>>> returned 0. The program uses SIGALRM signal. Could this be the cause ?
>>>>>
>>>>>
>>>>>
>>>> Yes, but the syscall should be silently restarted by default. This
>>>> patch should
>>>> fix the issue:
>>>>
>>>>
>>>>
>>> This one will compile:
>>>
>>> --- ksrc/skins/native/task.c (revision 3698)
>>> +++ ksrc/skins/native/task.c (working copy)
>>> @@ -410,11 +410,17 @@
>>> * A nesting count is maintained so that rt_task_suspend() and
>>> * rt_task_resume() must be used in pairs.
>>> *
>>> + * Receiving a Linux signal causes the suspended task to resume
>>> + * immediately.
>>> + *
>>> * @param task The descriptor address of the affected task. If @a task
>>> * is NULL, the current task is suspended.
>>> *
>>> * @return 0 is returned upon success. Otherwise:
>>> *
>>> + * - -EINTR is returned if a Linux signal has been received by the
>>> + * suspended task.
>>> + *
>>> * - -EINVAL is returned if @a task is not a task descriptor.
>>> *
>>> * - -EPERM is returned if the addressed @a task is not allowed to sleep
>>> @@ -463,9 +469,12 @@
>>> goto unlock_and_exit;
>>> }
>>>
>>> - if (task->suspend_depth++ == 0)
>>> + if (task->suspend_depth++ == 0) {
>>> xnpod_suspend_thread(&task->thread_base, XNSUSP,
>>> XN_INFINITE, XN_RELATIVE, NULL);
>>> + if (xnthread_test_info(&task->thread_base, XNBREAK))
>>> + err = -EINTR;
>>> + }
>>>
>>> unlock_and_exit:
>>>
>>>
>>>
>>>
>>
>
>
>
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