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Date: Mon, 26 Mar 2012 11:53:58 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-help] rt_pipe does not support POLLHUP on the Linux
 side
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To: Wolfgang Grandegger <wg@domain.hid>
Cc: xenomai-help <xenomai@xenomai.org>

On 03/26/2012 11:48 AM, Wolfgang Grandegger wrote:
> On 03/26/2012 11:38 AM, Wolfgang Grandegger wrote:
>> Hi Gilles,
>>
>> On 03/23/2012 02:14 PM, Gilles Chanteperdrix wrote:
>>> On 03/23/2012 10:59 AM, Gilles Chanteperdrix wrote:
>>>> On 03/23/2012 09:35 AM, Wolfgang Grandegger wrote:
>>>>> Hello,
>>>>>
>>>>> while playing with rt_pipe, I realized that a select()/poll() function
>>>>> does not unblock when the rt_pipe is deleted (via rt_pipe_delete) on the
>>>>> other end. I think this is because the poll callback does not support
>>>>> POLLHUP:
>>>>>
>>>>> http://www.rts.uni-hannover.de/xenomai/lxr/source/ksrc/nucleus/pipe.c#1024
>>>>>
>>>>> Is this by purpose? At least a blocking read() works as expected. It
>>>>> does unblock and return 0 in that case.
>>>>
>>>> rt_pipes are deprecated, we are not going to add new features to them
>>>> now. Please do not use them for new developments. We now have socket
>>>> based RTIPCs. See examples/rtdm/profiles/ipc.
>>
>> Ah, I was not aware of that. This solution does also work for any skin
>> (and does not require to misuse the native skin any more).
> 
> BTW, is there another interface (whith less overhead) to signal Linux
> thread from RT threads to trigger some work, e.g. for reading from shmem?

The simplest thing to do in such a case is to make the "Linux" thread a
Xenomai thread but running with the SCHED_OTHER policy, you can then use
simpler IPCs such as semaphores. Starting with Xenomai 2.6.0, such a
thread is guaranteed to return to secondary mode as soon as possible.

-- 
					    Gilles.