(8/12/13 3:34 PM), Toshi Kani wrote: > lock_device_hotplug() serializes hotplug & online/offline operations. > The lock is held in common sysfs online/offline interfaces and ACPI > hotplug code paths. > > try_offline_node() off-lines a node if all memory sections and cpus > are removed on the node. It is called from acpi_processor_remove() > and acpi_memory_remove_memory()->remove_memory() paths, both of which > are in the ACPI hotplug code. > > try_offline_node() calls stop_machine() to stop all cpus while checking > all cpu status with the assumption that the caller is not protected from > CPU hotplug or CPU online/offline operations. However, the caller is > always serialized with lock_device_hotplug(). Also, the code needs to > be properly serialized with a lock, not by stopping all cpus at a random > place with stop_machine(). > > This patch removes the use of stop_machine() in try_offline_node() and > adds comments to try_offline_node() and remove_memory() that > lock_device_hotplug() is required. This patch need more verbose explanation. check_cpu_on_node() traverse cpus and cpu hotplug seems to use cpu_hotplug_driver_lock() instead of lock_device_hotplug(). That said, the race is not happen against another memeory happen. It's likely happen another cpu hotplug. So commenting remove_memory() doesn't make much sense. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>