linux-kernel - Problem with wake_up using real-time scheduling

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Message-ID: <233789ed0906300144q209886b3qfb6737175a3660a0@mail.gmail.com>
Date:	Tue, 30 Jun 2009 10:44:35 +0200
From:	Zoltan Bus <zoltan.bus@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Problem with wake_up using real-time scheduling

Hello,

I have a problem on kernel 2.6.26.3. I have a real-time task which
uses the select system call to poll my audio driver. The sleeping task
is waken up by wake_up() from an interrupt handler.
The problem is, that the wake_up() function  sometimes does not wake
up the task if real-time priority is used.

The try_to_wake_up() returns from the out_running section, because of the check

      if (p->se.on_rq)
              goto out_running;

There are no other tasks running when the poll function is called.

Is this a known problem? Is it fixed somehow in newer versions?
Unfortunately I do not have the possibility to change the newest kernel version.
I am a newbie at linux, thank you very much for your help.

Zoltan
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