ia64 and x86_64 use the number of disabled local apics in ACPI tables MADT
to determine the number of potentially hot-pluggable cpus. The implementation
-should only rely on this to count the #of cpus, but *MUST* not rely on the
-apicid values in those tables for disabled apics. In the event BIOS doesnt
+should only rely on this to count the # of cpus, but *MUST* not rely on the
+apicid values in those tables for disabled apics. In the event BIOS doesn't
mark such hot-pluggable cpus as disabled entries, one could use this
parameter "additional_cpus=x" to represent those cpus in the cpu_possible_map.
A: The following happen, listed in no particular order :-)
- A notification is sent to in-kernel registered modules by sending an event
- CPU_DOWN_PREPARE
+ CPU_DOWN_PREPARE or CPU_DOWN_PREPARE_FROZEN, depending on whether or not the
+ CPU is being offlined while tasks are frozen due to a suspend operation in
+ progress
- All process is migrated away from this outgoing CPU to a new CPU
- All interrupts targeted to this CPU is migrated to a new CPU
- timers/bottom half/task lets are also migrated to a new CPU
- Once all services are migrated, kernel calls an arch specific routine
__cpu_disable() to perform arch specific cleanup.
- Once this is successful, an event for successful cleanup is sent by an event
- CPU_DEAD.
+ CPU_DEAD (or CPU_DEAD_FROZEN if tasks are frozen due to a suspend while the
+ CPU is being offlined).
"It is expected that each service cleans up when the CPU_DOWN_PREPARE
notifier is called, when CPU_DEAD is called its expected there is nothing
switch (action) {
case CPU_ONLINE:
+ case CPU_ONLINE_FROZEN:
foobar_online_action(cpu);
break;
case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
foobar_dead_action(cpu);
break;
}