Hi, I ran into some issue with the NMI watchdog not firing in a deadlock situation. After some debugging I found the source of the problem.
The NMI watchdog is currently subject, like any other events, to interrupt throttling. The heart of the problem is that if you are deadlocked on a CPU with interrupts masked, the timer interrupt won't fire, therefore the hwc->interrupts field won't be reset. Then, depending on the max sampling rate, you could eventually fail the max interrupt rate test in __pfm_overflow_handler() and perf_events would throttle, i.e., stop, the NMI watchdog event before the 5s delay to panic. Thus, you would never get the panic. I ran into this problem myself. This is a serious issue because perf_events must ensure the watchdog can always fire, regardless of the interrupt masking situation. Look like one way of solving the problem would be to mark the NMI watchdog event as immune to throttling. The event being internal to the kernel we could trust the event setup from perf_event_create_kernel_counter(). ------------------------------------------------------------------------------ This SF.net email is sponsored by Make an app they can't live without Enter the BlackBerry Developer Challenge http://p.sf.net/sfu/RIM-dev2dev _______________________________________________ perfmon2-devel mailing list perfmon2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/perfmon2-devel
