On 04/10/2012 02:33 PM, Roberto Bielli wrote:
> Il 10/04/2012 13:49, Gilles Chanteperdrix ha scritto:
>> On 04/10/2012 12:39 PM, Roberto Bielli wrote:
>>> Hi Gilles,
>>> i tried your code but th behavior is the same.
>>> Then i tried a linux base app and works correctly.
>> In the exact same conditions? With the crunching task running with
>> SCHED_FIFO, priority 1, and the periodic task running with SCHED_FIFO,
>> priority 99, and the linux real-time throttling disabled?
> Yes, and i see that every LATCH ( about ~10ms ) period the task with 
> higher priority is wakeup.
> So a task with lower priority is interrupted by timer interrupt and 
> reschedule the task with higher priority.
The only thing I can think is that the timer interrupt in fact stays 
masked. You can try the following patch:

diff --git a/arch/arm/plat-mxc/irq.c b/arch/arm/plat-mxc/irq.c                  
index 8aee763..7e4cc2e 100644                                                   
--- a/arch/arm/plat-mxc/irq.c                                                   
+++ b/arch/arm/plat-mxc/irq.c                                                   
@@ -94,12 +94,14 @@ EXPORT_SYMBOL(mxc_set_irq_fiq);                             
 static void mxc_mask_irq(unsigned int irq)                                     
        __raw_writel(irq, avic_base + AVIC_INTDISNUM);                          
+       __raw_readl(avic_base + AVIC_INTDISNUM);                                
 /* Enable interrupt number "irq" in the AVIC */                                
 static void mxc_unmask_irq(unsigned int irq)                                   
        __raw_writel(irq, avic_base + AVIC_INTENNUM);                           
+       __raw_readl(avic_base + AVIC_INTENNUM);                                 
 static struct irq_chip mxc_avic_chip = {                                       

If I had to debug this issue, I would look at all the timer and 
interrupt controller registers value, to see what is wrong.

You can also try the plain linux example with CONFIG_IPIPE on, but 

Other than that, without access to the board, it is hard for me to 
debug further, so I am afraid you are on your own.


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