Hello everyone, This is the version 2 of the refcount based cpu-hotplug "locking" implementation.
It incorporates the review comments from the first posting which can be found here --> http://lkml.org/lkml/2007/10/16/118. Changes since v1: - !CONFIG_HOTPLUG_CPU part is now handled correctly, thanks to the patch from Paul Jackson. - The cpu_hotplug_begin() uses a waitqueue instead of a completion struct where a writer can wait while there are active readers in the system. - Provided a new API's cpu_maps_update_begin(), cpu_maps_update_done() for serializing the updates to cpu_present_map and cpu_online_map. Thus threads which update the cpu_present_map should now call cpu_maps_update_begin instead of lock_cpu_hotplug(), since they play the role of writers. - pseries_processor_add() , pseries_processor_remove() now use cpu_maps_update_begin()/cpu_maps_update_done() in place of lock_cpu_hotplug()/unlock_cpu_hotplug(). - Replaced the workqueue_mutex with workqueue_lock, which is a spinlock and guards the workqueues list. - Updated Documentation/cpu-hotplug.txt to reflect get_online_cpus(), put_online_cpus() in place of the old lock_cpu_hotplug(), unlock_cpu_hotplug(). I'm Cc'ing the different subsystem maintainers who might be affected by the changes in the patchstack. Especially if they rely on lock_cpu_hotplug() to provide them protection for their local data structures as well. The patchstack which is based against 2.6.23-mm1 has behaved well when it was stress tested with kernbench running while continuously performing cpu-hotplug operations on i386, x86_64 and ppc64. Awaiting your feedback. Thanks and Regards gautham. -- Gautham R Shenoy Linux Technology Center IBM India. "Freedom comes with a price tag of responsibility, which is still a bargain, because Freedom is priceless!" - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
