diff options
Diffstat (limited to 'Documentation/cpu-hotplug.txt')
| -rw-r--r-- | Documentation/cpu-hotplug.txt | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt index a741f658a3c9..ba0aacde94fb 100644 --- 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. |