On Fri, Jun 21, 2013 at 12:21 PM, Tom Cook <tom.k.cook@xxxxxxxxx> wrote: [snip] > I think I'm nearly starting to get my head around what's going on > here. The USB driver uses FIQs, which normally isn't a problem > because nothing would interrupt the FIQ handler (or if it did, it > wouldn't generate a page fault). But cyclictest runs at a higher > priority than the USB handler and generates page faults (at least when > it is initialising). Eventually it interrupts a USB FIQ handler and > the memory manager doesn't know what to do with a page fault in a FIQ > handler, so it oopses. Does that sound about right? Or, of course, perhaps the tracer is instrumenting the USB FIQ handler with a hardware watchpoint. These turn up as data aborts, which are unhandled in FIQ mode. Some evidence for this is that if I use set_ftrace_filter to restrict the tracing to only a few system functions then the crash doesn't happen. Regards, Tom -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
