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Date: Wed, 16 Nov 2005 06:45:23 +0100
From: Philippe Gerum <rpm@xenomai.org>
MIME-Version: 1.0
Subject: Re: [Xenomai-help] Strange pipe behaviour
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To: =?ISO-8859-1?Q?Ignacio_Garc=EDa_P=E9rez?= <iggarpe@domain.hid>
Cc: xenomai@xenomai.org

Ignacio Garc=EDa P=E9rez wrote:
> Hi,
>=20
> I have the following piece of code:
>=20
> RT_PIPE_MSG *msg;
>=20
> while ((r =3D rt_pipe_receive(&mypipe, &msg, TM_INFINITE)) >=3D 0) {
>     /* whatever */
>     rt_pipe_free(msg);
> }
>=20
> When that thread enters, it blocks, as expected, in the rt_pipe_receive
> call.
>=20
> Then, from user space, I do:
>=20
> echo -en "\x00" > /dev/rtp0
>=20
> What happens is:
>=20
> 1- rt_pipe_receive returns with r >=3D 0.
> 2- /* whatever */
> 3- Message is freed using rt_pipe_free.
> 4- Next call to rt_pipe_receive returns with r =3D -EINTR.
>=20
> The only explanation I could come up with is that when the pipe is
> closed by the user mode process, the rt_pipe_receive tells the rt task
> by returning -EINTR. Is this right?.

Yes.

  According to the docs, -EINTR is
> only returned if rt_task_unblock() has been called...
>=20

Actually, this is what happened through the internal interface.
driver::release(pipe) -> nucleus::unblock(sleepers_on_pipe)

> Nacho.
>=20
>=20
>=20
>=20
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>=20


--=20

Philippe.