On Tue, May 10, 2022 at 08:38:22PM +1000, Nicholas Piggin wrote: > Excerpts from Ricardo Neri's message of May 6, 2022 9:59 am: > > Certain implementations of the hardlockup detector require support for > > Inter-Processor Interrupt shorthands. On x86, support for these can only > > be determined after all the possible CPUs have booted once (in > > smp_init()). Other architectures may not need such check. > > > > lockup_detector_init() only performs the initializations of data > > structures of the lockup detector. Hence, there are no dependencies on > > smp_init(). >
Thank you for your feedback Nicholas! > I think this is the only real thing which affects other watchdog types? Also patches 18 and 19 that decouple the NMI watchdog functionality from perf. > > Not sure if it's a big problem, the secondary CPUs coming up won't > have their watchdog active until quite late, and the primary could > implement its own timeout in __cpu_up for secondary coming up, and > IPI it to get traces if necessary which is probably more robust. Indeed that could work. Another alternative I have been pondering is to boot the system with the perf-based NMI watchdog enabled. Once all CPUs are up and running, switch to the HPET-based NMI watchdog and free the PMU counters. > > Acked-by: Nicholas Piggin <npig...@gmail.com> Thank you! BR, Ricardo
