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[SRX] Kernel crash after enabling ukern commands



Article ID: KB33960 KB Last Updated: 23 Aug 2019Version: 1.0

On SRX branch series, the kernel might crash after enabling the ukern commands.


If any of the ukern commands ('dedicated-ukern-cpu' or 'realtime-ukern-thread') are active in the configuration; upon reboot, login, or even committing a configuration, the kernel might crash showing the following watchdog panic messages:

SRX-LAB (ttyu0)


NMI Exception on core:0
Watchdog status, core 0: 0xfffe66ffffb
FPA INT Summery: 0x0
Trapframe Register Dump:
zero: 0000000000000000  at: 0000000000000000  v0: 0000000000000004  v1: ffffffffc495aaa2
Stack trace:
_mtx_lock_sleep+0x158 (0x50808ce0,0x80da85e8,0xffff8010,0xffff8010) ra 0x802511b8 sz 32

For this crash, '_mtx_lock_sleep' was the first function in the stack trace.  For other crashes it can be  'smp_rendezvous_action', 'smp_rendezvous_action_selected'  or 'smp_barrier'.


When enabling 'set chassis dedicated-ukern-cpu', the watchdog panic can easily run into a race condition of atomic operation than the 'set chassis realtime-ukern-thread'.

The panic occurs when multiple threads operate the same counter.

Also, the match to the said behavior can be confirmed by checking the output of the "last reboot reason" in 'show chassis routing-engine':
root@SRX-LAB> show chassis routing-engine 

Last reboot reason 0x1000:reboot due to panic


This issue is fixed in the following Junos versions:

  • 12.3X48-D75
  • 15.1X49-D90
Modification History:

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