Hello all,

I am having an issue with a "lost" interrupt in an RTDM driver. This is a long story so I will try to summarize:

Hardware description -
I have a Geode2 based PC/104 stack with CAN and ADC/DAC cards. The motherboard implements a standard XT-PIC in its super io. The system is running Xenomai 2.2.1 with a Gentoo  Linux 2.6.17 kernel. There are several external devices on the CAN bus to load the bus with traffic.

Software description -
I have two RTDM drivers that provide simple ioctl() interfaces to the application. One driver supports two CAN controllers. (PCAN/SJA1000. I implemented this driver many months before RTCAN was available. Sorry I couldn't wait, paying customer and all. ;-) The other driver supports a ADC/DAQ card. The application runs several Xenomai tasks using message queues for communication.

Failure Description -
The application starts. I can see IRQ lines being raised and lowered as interrupts are handled. The application runs normally. After about one or two minutes depending on the bus load, I "lose" the IRQ15 interrupt. My interrupt service routine is never called and the interrupt chain is broken for that device. I have traced the IRQ lines from the devices on the oscilloscope and see that the IRQ goes high, but is never acknowledged. (See attached. I added labels to each trace.) This failure is sporadic and seems to depend on all three devices generating interrupts in the system.

Theory -
The interrupt is never acknowledged because the PIC did not notify the processor or software never acknowledged the PIC.

Testing approach -
I need to determine if the hardware or software has lost the interrupt. I would tend to suspect software first so I decided to start there. I am using the parallel port pins as GPIO output and trying to instrument the low-level ADEOS/Xenomai interrupt handling. If I catch the interrupt soon enough in the interrupt pipeline I can determine that some software issue is preventing my isr from running. If no interrupt ever occurs then I can suspect the hardware.

Assumptions -
ADEOS/Xenomai/RTDM catches the interrupt and propagates it to my isr. If my isr is the first level interrupt handler I am out of luck.

Any thoughts or suggestions are appreciated.

Thanks,
Sean