Merge branches 'release', 'asus', 'sony-laptop' and 'thinkpad' into release

[pandora-kernel.git] / Documentation / cpu-hotplug.txt

diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index b6d24c2..ba0aacd 100644 (file)
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -50,7 +50,7 @@ additional_cpus=n (*) Use this to limit hotpluggable cpus. This option sets
                        cpu_possible_map = cpu_present_map + additional_cpus
 
 (*) Option valid only for following architectures
-- x86_64, ia64, s390
+- x86_64, ia64
 
 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
@@ -109,12 +109,13 @@ Never use anything other than cpumask_t to represent bitmap of CPUs.
        for_each_cpu_mask(x,mask) - Iterate over some random collection of cpu mask.
 
        #include <linux/cpu.h>
-       lock_cpu_hotplug() and unlock_cpu_hotplug():
+       get_online_cpus() and put_online_cpus():
 
-The above calls are used to inhibit cpu hotplug operations. While holding the
-cpucontrol mutex, cpu_online_map will not change. If you merely need to avoid
-cpus going away, you could also use preempt_disable() and preempt_enable()
-for those sections. Just remember the critical section cannot call any
+The above calls are used to inhibit cpu hotplug operations. While the
+cpu_hotplug.refcount is non zero, the cpu_online_map will not change.
+If you merely need to avoid cpus going away, you could also use
+preempt_disable() and preempt_enable() for those sections.
+Just remember the critical section cannot call any
 function that can sleep or schedule this process away. The preempt_disable()
 will work as long as stop_machine_run() is used to take a cpu down.
 
@@ -220,7 +221,9 @@ A: The following happen, listed in no particular order :-)
   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 processes are migrated away from this outgoing CPU to new CPUs.
+  The new CPU is chosen from each process' current cpuset, which may be
+  a subset of all online CPUs.
 - 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