Symptoms
A tmm thread might stall while yielding the CPU, and trigger a failsafe restart of the tmm process. A core file might be generated without any message logged in /var/log/*.
High resolution timers (hrtimer) may be lost.
Impact
Traffic disrupted while tmm restarts.
Conditions
This occurs when data in kernel hrtimer module is corrupted by a kernel bug, so a tmm thread may fail to wake at the appropriate time after having entered a planned short sleep.
The precise details in this particular case are not knowable.
Workaround
Very rarely, this might take a long time, in which case there is no mitigation except to wait for the operation to complete.
Alternatively, the unit might remain offline, in which rebooting the system is the better option.
Fix Information
Fixed kernel issue that led to an unanticipated restart of tmm due to heartbeat failure.
