Hi Lai,
Could you share the show version output and modules/Cards in the device. As Leo has posted most likely to be a Bug.
Please refer the below URL for your reference.
http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_tech_note09186a00800f67db.shtml
Cisco processors have timers that guard against certain types of system hangs. The CPU periodically resets a watchdog timer. The watchdog timer basically controls the time of each process. If the timer is not reset, a trap occurs. If a process is longer than it must be, the watchdog timer is used to escape from this process.
This only occurs if something goes wrong. Based on the situation, the router can reset itself, or recover from the failure and generate an error message in the console logs, which looks like this:
*** Watch Dog Timeout ***
PC = 0x6022536C, SP = 0x00000000
or
%SYS-2-WATCHDOG: Process aborted on watchdog timeout, process = Exec
*** System received a Software forced crash ***
signal = 0x17, code = 0x24, context= 0x60ceca60
Regards,
Sathvik K V