Messages in this thread | | | Date | Tue, 31 Oct 2017 14:50:59 -0400 | From | Don Zickus <> | Subject | Re: Crashes in perf_event_ctx_lock_nested |
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On Tue, Oct 31, 2017 at 10:16:22AM -0700, Guenter Roeck wrote: > On Tue, Oct 31, 2017 at 02:48:50PM +0100, Peter Zijlstra wrote: > > On Mon, Oct 30, 2017 at 03:45:12PM -0700, Guenter Roeck wrote: > > > I added some logging and a long msleep() in hardlockup_detector_perf_cleanup(). > > > Here is the result: > > > > > > [ 0.274361] NMI watchdog: ############ hardlockup_detector_perf_init > > > [ 0.274915] NMI watchdog: ############ hardlockup_detector_event_create(0) > > > [ 0.277049] NMI watchdog: ############ hardlockup_detector_perf_cleanup > > > [ 0.277593] NMI watchdog: ############ hardlockup_detector_perf_enable(0) > > > [ 0.278027] NMI watchdog: ############ hardlockup_detector_event_create(0) > > > [ 1.312044] NMI watchdog: ############ hardlockup_detector_perf_cleanup done > > > [ 1.385122] NMI watchdog: ############ hardlockup_detector_perf_enable(1) > > > [ 1.386028] NMI watchdog: ############ hardlockup_detector_event_create(1) > > > [ 1.466102] NMI watchdog: ############ hardlockup_detector_perf_enable(2) > > > [ 1.475536] NMI watchdog: ############ hardlockup_detector_event_create(2) > > > [ 1.535099] NMI watchdog: ############ hardlockup_detector_perf_enable(3) > > > [ 1.535101] NMI watchdog: ############ hardlockup_detector_event_create(3) > > > > > [ 7.222816] NMI watchdog: ############ hardlockup_detector_perf_disable(0) > > > [ 7.230567] NMI watchdog: ############ hardlockup_detector_perf_disable(1) > > > [ 7.243138] NMI watchdog: ############ hardlockup_detector_perf_disable(2) > > > [ 7.250966] NMI watchdog: ############ hardlockup_detector_perf_disable(3) > > > [ 7.258826] NMI watchdog: ############ hardlockup_detector_perf_enable(1) > > > [ 7.258827] NMI watchdog: ############ hardlockup_detector_perf_cleanup > > > [ 7.258831] NMI watchdog: ############ hardlockup_detector_perf_enable(2) > > > [ 7.258833] NMI watchdog: ############ hardlockup_detector_perf_enable(0) > > > [ 7.258834] NMI watchdog: ############ hardlockup_detector_event_create(2) > > > [ 7.258835] NMI watchdog: ############ hardlockup_detector_event_create(0) > > > [ 7.260169] NMI watchdog: ############ hardlockup_detector_perf_enable(3) > > > [ 7.260170] NMI watchdog: ############ hardlockup_detector_event_create(3) > > > [ 7.494251] NMI watchdog: ############ hardlockup_detector_event_create(1) > > > [ 8.287135] NMI watchdog: ############ hardlockup_detector_perf_cleanup done > > > > > > Looks like there are a number of problems: hardlockup_detector_event_create() > > > creates the event data structure even if it is already created, > > > > Right, that does look dodgy. And on its own should be fairly straight > > forward to cure. But I'd like to understand the rest of it first. > > > > > and hardlockup_detector_perf_cleanup() runs unprotected and in > > > parallel to the enable/create functions. > > > > Well, looking at the code, cpu_maps_update_begin() aka. > > cpu_add_remove_lock is serializing cpu_up() and cpu_down() and _should_ > > thereby also serialize cleanup vs the smp_hotplug_thread operations. > > > > Your trace does indeed indicate this is not the case, but I cannot, from > > the code, see how this could happen. > > > > Could you use trace_printk() instead and boot with > > "trace_options=stacktrace" ? > > > Attached. Let me know if you need more information. Note this is with > msleep(1000) in the cleanup function to avoid the crash. > > > > ALso, the following message is seen twice. > > > > > > [ 0.278758] NMI watchdog: Enabled. Permanently consumes one hw-PMU counter. > > > [ 7.258838] NMI watchdog: Enabled. Permanently consumes one hw-PMU counter. > > > > > > I don't offer a proposed patch since I have no idea how to best solve the > > > problem. > > > > > > Also, is the repeated enable/disable/cleanup as part of the normal boot > > > really necessary ? > > > > That's weird, I don't see that on my machines. We very much only bring > > up the CPUs _once_. Also note they're 7s apart. Did you do something > > funny like resume-from-disk or so? > > No, just whatever Chrome OS does when it starts the kernel. The hardware > used in this test is a Google Pixelbook, though we have also seen the problem > with other Chromebooks.
Is Chrome OS, changing the default timeout from 10s to something else? That would explain it as a script is executed late in the boot cycle and explain the quick restart.
Cheers, Don
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