From: Gautham R Shenoy Date: Wed, 9 May 2007 09:34:03 +0000 (-0700) Subject: Define and use new events,CPU_LOCK_ACQUIRE and CPU_LOCK_RELEASE X-Git-Tag: v2.6.22-rc1~238 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=baaca49f415b25fdbe2a8f3c22b39929e450fbfd;p=pandora-kernel.git Define and use new events,CPU_LOCK_ACQUIRE and CPU_LOCK_RELEASE This is an attempt to provide an alternate mechanism for postponing a hotplug event instead of using a global mechanism like lock_cpu_hotplug. The proposal is to add two new events namely CPU_LOCK_ACQUIRE and CPU_LOCK_RELEASE. The notification for these two events would be sent out before and after a cpu_hotplug event respectively. During the CPU_LOCK_ACQUIRE event, a cpu-hotplug-aware subsystem is supposed to acquire any per-subsystem hotcpu mutex ( Eg. workqueue_mutex in kernel/workqueue.c ). During the CPU_LOCK_RELEASE release event the cpu-hotplug-aware subsystem is supposed to release the per-subsystem hotcpu mutex. The reasons for defining new events as opposed to reusing the existing events like CPU_UP_PREPARE/CPU_UP_FAILED/CPU_ONLINE for locking/unlocking of per-subsystem hotcpu mutexes are as follow: - CPU_LOCK_ACQUIRE: All hotcpu mutexes are taken before subsystems start handling pre-hotplug events like CPU_UP_PREPARE/CPU_DOWN_PREPARE etc, thus ensuring a clean handling of these events. - CPU_LOCK_RELEASE: The hotcpu mutexes will be released only after all subsystems have handled post-hotplug events like CPU_DOWN_FAILED, CPU_DEAD,CPU_ONLINE etc thereby ensuring that there are no subsequent clashes amongst the interdependent subsystems after a cpu hotplugs. This patch also uses __raw_notifier_call chain in _cpu_up to take care of the dependency between the two consequetive calls to raw_notifier_call_chain. [akpm@linux-foundation.org: fix a bug] Signed-off-by: Gautham R Shenoy Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed