Re: Spurious interrupt on ARM.

On 01/11/13 17:20, Andrew Parlane wrote:
> Sorry, I should have been a bit more clear.
> First we skip the ISR by jumping to the spurious_IRQ label, and then we 
> switch stacks if necessary, then we have (line numbers may vary):
> 
> 941        // The return value from the handler (in r0) will indicate 
> whether a
> 942        // DSR is to be posted. Pass this together with a pointer to the
> 943        // interrupt object we have just used to the interrupt tidy 
> up routine.
> 944
> 945                              // don't run this for spurious interrupts!
> 946        cmp     v1,#CYGNUM_HAL_INTERRUPT_NONE
> 947        beq     17f
> 948        ldr     r1,.hal_interrupt_objects
> 949        ldr     r1,[r1,v1,lsl #2]
> 950        mov     r2,v6           // register frame
> 951
> 952        THUMB_MODE(r3,10)
> 953
> 954        bl      interrupt_end   // post any bottom layer handler
> 955                                // threads and call scheduler
> 956        ARM_MODE(r1,10)
> 957 17:
> 
> So it compares the result of hal_IRQ_handler (stored in v1) with 
> CYGNUM_HAL_INTERRUPT_NONE, and jumps forwards to label 17: which is 
> after interrupt_end. if it was a spurious IRQ.


Hmm. You're right. That is clearly wrong. Our own sources have the
following code, which is slightly different:

        // The return value from the handler (in r0) will indicate
whether a
        // DSR is to be posted. Pass this together with a pointer to the
        // interrupt object we have just used to the interrupt tidy up
routine.

        // For a spurious interrupt, pass a NULL object. interrupt_end()
will
        // handle that and still unlock the scheduler.
        cmp     v1,#CYGNUM_HAL_INTERRUPT_NONE
        moveq   r1,#0
        beq     17f
        ldr     r1,.hal_interrupt_objects
        ldr     r1,[r1,v1,lsl #2]
17:
        mov     r2,v6           // register frame


So interrupt_end does get called, but with a NULL interrupt object pointer.


-- 
Nick Garnett                                         Kernel Architect
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