Android suspend mode

What mechanism let the (OS) daemons know that the phone enters the sleep/suspend mode in Android?

Does the init process (which is the parent of all daemons) send a kill signal when the phone开发者_JS百科 switch to suspend mode?

This is controlled through wake locks. There isn't something deciding when to put the CPU to sleep; apps hold a wake lock to prevent it from going to sleep. If there are no wake locks being held, the CPU goes to sleep and will not come back out of sleep until an external event (button press, network activity, alarm) wakes it up.