On 1/11/2016 3:25 AM, Daniel Thompson wrote: > On 11/01/16 10:26, Mark Rutland wrote: >> Hi, >> >> On Sat, Jan 09, 2016 at 04:13:48PM -0800, Mario Smarduch wrote: >>> I'm trying to get HARDLOCKUP detector to work on arm (on foundation >>> model and Juno, but armv7 should have the same issue). Turns out there is no >>> PERF NMI support (HAVE_PERF_EVENTS_NMI), which I guess would be PMU NMI - I >>> tested overflow on cycle counter and PMU interrupts can be masked. HARDLOCKUP >>> assumes perf interrupts are non-maskable and uses the PMU to program an NMI to >>> detect hard lockup and that in turn drives softlockup detection. >>> >>> Is there something, someplace in ARM manuals that addresses this, searched the >>> manuals but couldn't find anything? >>> >>> Or other approaches that I'm not aware off or have floated on the mailing list. >> >> Russell and Daniel did some work [1,2] to use FIQs as NMIs on arm, for >> backtracing and PMU overflow. > > >> For arm64 the kernel always runs on the non-secure side, so we don't >> expect to have access to FIQ. It's possible to implement NMIs using >> priorities (which it looks like Daniel was looking into [3]). > > Thanks Mark. > > The blog post is still pretty much describes my ambitions and the > benefits these features can bring. It also has a link to a fairly > elderly kernel that contains all the features fully integrated. > > There are more patchsets for both ARM (if/f FIQ is available) and ARM64 > (if/f device has GICv3). However these only provide NMI backtrace. > > arm: http://thread.gmane.org/gmane.linux.kernel/2112583 > > arm64: http://thread.gmane.org/gmane.linux.kernel/2037735 (Mark's > link to my git repo is more up to date than this patchset) > > To get the hard lockup and profiling support upstream then my old code > to integrate NMIs into the irq subsystem (which was just a cut down > clone of the existing irq infrastructure) needs to be redesigned. > However I decided to put the rewrite on ice until I get the foundational > patches right. > > > Daniel. > Daniel, Mark - thanks for the info. I'll research the work done so far and probably comeback later. - Mario -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
