Re: Ingo's realtime_preempt patch causes kernel oops

[Yann . LEPROVOST]

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@xxxxxxxxxx           
             linux-kernel-owne                                          cc 
             r@xxxxxxxxxxxxxxx         Daniel Walker <dwalker@xxxxxxxxxx>, 
                                       linux-kernel@xxxxxxxxxxxxxxx, Ingo  
                                       Molnar <mingo@xxxxxxx>, Thomas      
             23/05/2006 19:00          Gleixner <tglx@xxxxxxxxxxxxx>       
                                                                   Subject 
                                       Re: Ingo's  realtime_preempt patch  
                                       causes kernel oops                  
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




On Tue, 2006-05-23 at 18:27 +0200, Yann.LEPROVOST@xxxxxxxxxx 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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