timer
This function only differs from del_timer on SMP: besides deactivating the timer it also makes sure the handler has finished executing on other CPUs.
Callers must prevent restarting of the timer, otherwise this function is meaningless. It must not be called from interrupt contexts. The caller must not hold locks which would prevent completion of the timer's handler. The timer's handler must not call add_timer_on. Upon exit the timer is not queued and the handler is not running on any CPU.
The function returns whether it has deactivated a pending timer or not.