Description

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

Symptoms

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)

login: 

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'.

Solution

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