Re: Crashes in perf_event_ctx_lock_nested

[Guenter Roeck]

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.

Guenter

---
# tracer: nop
#
#                              _-----=> irqs-off
#                             / _----=> need-resched
#                            | / _---=> hardirq/softirq
#                            || / _--=> preempt-depth
#                            ||| /     delay
#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
#              | |       |   ||||       |         |
       swapper/0-1     [000] ....     0.350933: hardlockup_detector_perf_init: ############ hardlockup_detector_perf_init
       swapper/0-1     [000] ....     0.350938: <stack trace>
 => kernel_init_freeable
 => kernel_init
 => ret_from_fork
       swapper/0-1     [000] ....     0.350942: hardlockup_detector_event_create: ############ hardlockup_detector_event_create(0)
       swapper/0-1     [000] ....     0.350946: <stack trace>
 => kernel_init_freeable
 => kernel_init
 => ret_from_fork
       swapper/0-1     [000] ....     0.352637: hardlockup_detector_perf_cleanup: ############ hardlockup_detector_perf_cleanup
       swapper/0-1     [000] ....     0.352641: <stack trace>
 => kernel_init_freeable
 => kernel_init
 => ret_from_fork
      watchdog/0-12    [000] ....     0.352649: hardlockup_detector_perf_enable: ############ hardlockup_detector_perf_enable(0)
      watchdog/0-12    [000] ....     0.352653: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/0-12    [000] ....     0.352655: hardlockup_detector_event_create: ############ hardlockup_detector_event_create(0)
      watchdog/0-12    [000] ....     0.352658: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
       swapper/0-1     [000] ....     1.394555: hardlockup_detector_perf_cleanup: ############ hardlockup_detector_perf_cleanup done
       swapper/0-1     [000] ....     1.394559: <stack trace>
 => kernel_init_freeable
 => kernel_init
 => ret_from_fork
      watchdog/1-15    [001] ....     1.534624: hardlockup_detector_perf_enable: ############ hardlockup_detector_perf_enable(1)
      watchdog/1-15    [001] ....     1.534636: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/1-15    [001] ....     1.534640: hardlockup_detector_event_create: ############ hardlockup_detector_event_create(1)
      watchdog/1-15    [001] ....     1.534646: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
      watchdog/2-21    [002] ....     1.637496: hardlockup_detector_perf_enable: ############ hardlockup_detector_perf_enable(2)
      watchdog/2-21    [002] ....     1.637505: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/2-21    [002] ....     1.637507: hardlockup_detector_event_create: ############ hardlockup_detector_event_create(2)
      watchdog/2-21    [002] ....     1.637510: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
      watchdog/3-27    [003] ....     1.742245: hardlockup_detector_perf_enable: ############ hardlockup_detector_perf_enable(3)
      watchdog/3-27    [003] ....     1.742253: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/3-27    [003] ....     1.742255: hardlockup_detector_event_create: ############ hardlockup_detector_event_create(3)
      watchdog/3-27    [003] ....     1.742258: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
      watchdog/0-12    [000] ....     7.535105: hardlockup_detector_perf_disable: ############ hardlockup_detector_perf_disable(0)
      watchdog/0-12    [000] ....     7.535108: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/1-15    [001] ....     7.535136: hardlockup_detector_perf_disable: ############ hardlockup_detector_perf_disable(1)
      watchdog/1-15    [001] ....     7.535138: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/2-21    [002] ....     7.535155: hardlockup_detector_perf_disable: ############ hardlockup_detector_perf_disable(2)
      watchdog/2-21    [002] ....     7.535157: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/3-27    [003] ....     7.535188: hardlockup_detector_perf_disable: ############ hardlockup_detector_perf_disable(3)
      watchdog/3-27    [003] ....     7.535190: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/2-21    [002] ....     7.535206: hardlockup_detector_perf_enable: ############ hardlockup_detector_perf_enable(2)
      watchdog/2-21    [002] ....     7.535221: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/2-21    [002] ....     7.535222: hardlockup_detector_event_create: ############ hardlockup_detector_event_create(2)
      watchdog/2-21    [002] ....     7.535223: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
      watchdog/2-21    [002] ....     7.535224: hardlockup_detector_event_create: ############## perf event for CPU 2 already created, skipping
      watchdog/2-21    [002] ....     7.535225: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
      watchdog/0-12    [000] ....     7.535225: hardlockup_detector_perf_enable: ############ hardlockup_detector_perf_enable(0)
      watchdog/1-15    [001] ....     7.535225: hardlockup_detector_perf_enable: ############ hardlockup_detector_perf_enable(1)
      watchdog/1-15    [001] ....     7.535228: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/0-12    [000] ....     7.535228: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/0-12    [000] ....     7.535229: hardlockup_detector_event_create: ############ hardlockup_detector_event_create(0)
      watchdog/1-15    [001] ....     7.535229: hardlockup_detector_event_create: ############ hardlockup_detector_event_create(1)
      watchdog/0-12    [000] ....     7.535232: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
      watchdog/1-15    [001] ....     7.535232: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
      watchdog/0-12    [000] ....     7.535233: hardlockup_detector_event_create: ############## perf event for CPU 0 already created, skipping
      watchdog/1-15    [001] ....     7.535233: hardlockup_detector_event_create: ############## perf event for CPU 1 already created, skipping
      watchdog/0-12    [000] ....     7.535236: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
      watchdog/1-15    [001] ....     7.535236: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
          sysctl-148   [000] ....     7.536879: hardlockup_detector_perf_cleanup: ############ hardlockup_detector_perf_cleanup
          sysctl-148   [000] ....     7.536881: <stack trace>
 => proc_watchdog_thresh
 => proc_sys_call_handler
 => proc_sys_write
 => __vfs_write
 => vfs_write
 => SyS_write
 => entry_SYSCALL_64_fastpath
      watchdog/3-27    [003] ....     7.536888: hardlockup_detector_perf_enable: ############ hardlockup_detector_perf_enable(3)
      watchdog/3-27    [003] ....     7.536890: <stack trace>
 => kthread
 => ret_from_fork
      watchdog/3-27    [003] ....     7.536891: hardlockup_detector_event_create: ############ hardlockup_detector_event_create(3)
      watchdog/3-27    [003] ....     7.536892: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
      watchdog/3-27    [003] ....     7.536893: hardlockup_detector_event_create: ############## perf event for CPU 3 already created, skipping
      watchdog/3-27    [003] ....     7.536895: <stack trace>
 => smpboot_thread_fn
 => kthread
 => ret_from_fork
          sysctl-148   [000] ....     8.551925: hardlockup_detector_perf_cleanup: ############ hardlockup_detector_perf_cleanup done
          sysctl-148   [000] ....     8.551928: <stack trace>
 => proc_watchdog_thresh
 => proc_sys_call_handler
 => proc_sys_write
 => __vfs_write
 => vfs_write
 => SyS_write
 => entry_SYSCALL_64_fastpath