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authorGautham R Shenoy <ego@in.ibm.com>2007-05-09 02:34:03 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-09 12:30:51 -0700
commitbaaca49f415b25fdbe2a8f3c22b39929e450fbfd (patch)
treeb152b4235fc07fe56619bd3a2e975e5ca90b8c5b /include/linux/notifier.h
parent6f7cc11aa6c7d5002e16096c7590944daece70ed (diff)
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 <ego@in.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/notifier.h')
-rw-r--r--include/linux/notifier.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index e34221bf8946..1903e5490c04 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -194,6 +194,8 @@ extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
#define CPU_DOWN_PREPARE 0x0005 /* CPU (unsigned)v going down */
#define CPU_DOWN_FAILED 0x0006 /* CPU (unsigned)v NOT going down */
#define CPU_DEAD 0x0007 /* CPU (unsigned)v dead */
+#define CPU_LOCK_ACQUIRE 0x0008 /* Acquire all hotcpu locks */
+#define CPU_LOCK_RELEASE 0x0009 /* Release all hotcpu locks */
#endif /* __KERNEL__ */
#endif /* _LINUX_NOTIFIER_H */