task delete and semaphore

[WuHao]

Paul Whitfield 写道:
> Please keep this discussion on the RTEMS mailing list,
> as that way people who know about the internals of
> termios can respond
>
>>>> How does the task to be deleted get all resources it holds?
>>>> Typically when the task holds tty's write mutex.
>>>>
>>>
>>> As described in the manual, you should signal the task to clean up
>> ~~~~~
>> Suppose the task to be deleted gets CPU and begins to do clean up.
>> But it is holding a tty write mutex(osem), how can it release the 
>> mutex since
>> termios does not provide any directive to do so?
>
> I hope I am not missing something here!
>
> The point is you should not delete a task by calling rtems_task_delete
> from ANOTHER task.
>
> You should send a message, event or signal to the task which then
> cleans up and deletes itself. This includes releasing any held
> semaphore and closing any open termios ports.
>
> This message will only be received by the task to be
> deleted when it has *finished* its termios processing,
> and therefore at that point it will not be holding
> semaphores or other resources.
>
Is that to say:
Task A wants to delete Task B.
    1.Task A is not allowed to delete Task B by calling rtems_task_delete;
    2.Task A may delete Task B by send a message, event or signal to latter.
    2.If Task B does not know the time when Task A will send a message, 
and indeed Task A wants to delete Task B anytime, Task B must keep 
receiving message as soon as it has finished a libc processing?And howto?
Thanks.

> Looking at rtems_termios_write, it will release
> the semaphore tty->osem
>
> I hope that makes sense.
>
>
> Regards
>
> Paul
>
>
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