Re: Ingo's realtime_preempt patch causes kernel oops

Yann.LEPROVOST
2006-05-23T17:16:36Z

Currently there are only system timer and debug serial unit registered on
irq line 1.
Debug serial unit is used as the console !

Steven Rostedt
<rostedt@goodmis.
org> To
Sent by: Yann.LEPROVOST@wavecom.fr
linux-kernel-owne cc
r@vger.kernel.org Daniel Walker <dwalker@mvista.com>,
linux-kernel@vger.kernel.org, Ingo
Molnar <mingo@elte.hu>, Thomas
23/05/2006 19:00 Gleixner <tglx@linutronix.de>
Subject
Re: Ingo's realtime_preempt patch
causes kernel oops

On Tue, 2006-05-23 at 18:27 +0200, Yann.LEPROVOST@wavecom.fr wrote:
> I forgot to say that I let SA_SHIRQ as the IRQ line is shared...
> It seems to work correctly...

What shares it?

Reason I ask, is that this irq is now running in true interrupt context,
and that on PREEMPT_RT the spin_locks are mutexes and can schedule. So
if another device is sharing this irq, then its interrupt handler will
be running in interrupt context, and if it grabs a spin_lock than is not
a raw_spinlock_t then you will have a crash.

This won't be a problem if you only turn on Hard irqs as threads and
don't do the PREEMPT_RT.

-- Steve

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