From 6f7cc11aa6c7d5002e16096c7590944daece70ed Mon Sep 17 00:00:00 2001 From: Gautham R Shenoy Date: Wed, 9 May 2007 02:34:02 -0700 Subject: Extend notifier_call_chain to count nr_calls made Since 2.6.18-something, the community has been bugged by the problem to provide a clean and a stable mechanism to postpone a cpu-hotplug event as lock_cpu_hotplug was badly broken. This is another proposal towards solving that problem. This one is along the lines of the solution provided in kernel/workqueue.c Instead of having a global mechanism like lock_cpu_hotplug, we allow the subsytems to define their own per-subsystem hot cpu mutexes. These would be taken(released) where ever we are currently calling lock_cpu_hotplug(unlock_cpu_hotplug). Also, in the per-subsystem hotcpu callback function,we take this mutex before we handle any pre-cpu-hotplug events and release it once we finish handling the post-cpu-hotplug events. A standard means for doing this has been provided in [PATCH 2/4] and demonstrated in [PATCH 3/4]. The ordering of these per-subsystem mutexes might still prove to be a problem, but hopefully lockdep should help us get out of that muddle. The patch set to be applied against linux-2.6.19-rc5 is as follows: [PATCH 1/4] : Extend notifier_call_chain with an option to specify the number of notifications to be sent and also count the number of notifications actually sent. [PATCH 2/4] : Define events CPU_LOCK_ACQUIRE and CPU_LOCK_RELEASE and send out notifications for these in _cpu_up and _cpu_down. This would help us standardise the acquire and release of the subsystem locks in the hotcpu callback functions of these subsystems. [PATCH 3/4] : Eliminate lock_cpu_hotplug from kernel/sched.c. [PATCH 4/4] : In workqueue_cpu_callback function, acquire(release) the workqueue_mutex while handling CPU_LOCK_ACQUIRE(CPU_LOCK_RELEASE). If the per-subsystem-locking approach survives the test of time, we can expect a slow phasing out of lock_cpu_hotplug, which has not yet been eliminated in these patches :) This patch: Provide notifier_call_chain with an option to call only a specified number of notifiers and also record the number of call to notifiers made. The need for this enhancement was identified in the post entitled "Slab - Eliminate lock_cpu_hotplug from slab" (http://lkml.org/lkml/2006/10/28/92) by Ravikiran G Thirumalai and Andrew Morton. This patch adds two additional parameters to notifier_call_chain API namely - int nr_to_calls : Number of notifier_functions to be called. The don't care value is -1. - unsigned int *nr_calls : Records the total number of notifier_funtions called by notifier_call_chain. The don't care value is NULL. [michal.k.k.piotrowski@gmail.com: build fix] Credit: Andrew Morton Signed-off-by: Gautham R Shenoy Signed-off-by: Michal Piotrowski Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/notifier.h | 52 ++++++++++++++++++++++++++++-------------------- 1 file changed, 30 insertions(+), 22 deletions(-) (limited to 'include/linux') diff --git a/include/linux/notifier.h b/include/linux/notifier.h index 10a43ed0527e..e34221bf8946 100644 --- a/include/linux/notifier.h +++ b/include/linux/notifier.h @@ -112,32 +112,40 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); #ifdef __KERNEL__ -extern int atomic_notifier_chain_register(struct atomic_notifier_head *, - struct notifier_block *); -extern int blocking_notifier_chain_register(struct blocking_notifier_head *, - struct notifier_block *); -extern int raw_notifier_chain_register(struct raw_notifier_head *, - struct notifier_block *); -extern int srcu_notifier_chain_register(struct srcu_notifier_head *, - struct notifier_block *); - -extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *, - struct notifier_block *); -extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *, - struct notifier_block *); -extern int raw_notifier_chain_unregister(struct raw_notifier_head *, - struct notifier_block *); -extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *, - struct notifier_block *); - -extern int atomic_notifier_call_chain(struct atomic_notifier_head *, +extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, + struct notifier_block *nb); +extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, + struct notifier_block *nb); +extern int raw_notifier_chain_register(struct raw_notifier_head *nh, + struct notifier_block *nb); +extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, + struct notifier_block *nb); + +extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, + struct notifier_block *nb); +extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, + struct notifier_block *nb); +extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, + struct notifier_block *nb); +extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, + struct notifier_block *nb); + +extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, unsigned long val, void *v); -extern int blocking_notifier_call_chain(struct blocking_notifier_head *, +extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh, + unsigned long val, void *v, int nr_to_call, int *nr_calls); +extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, unsigned long val, void *v); -extern int raw_notifier_call_chain(struct raw_notifier_head *, +extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh, + unsigned long val, void *v, int nr_to_call, int *nr_calls); +extern int raw_notifier_call_chain(struct raw_notifier_head *nh, unsigned long val, void *v); -extern int srcu_notifier_call_chain(struct srcu_notifier_head *, +extern int __raw_notifier_call_chain(struct raw_notifier_head *nh, + unsigned long val, void *v, int nr_to_call, int *nr_calls); +extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, unsigned long val, void *v); +extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh, + unsigned long val, void *v, int nr_to_call, int *nr_calls); #define NOTIFY_DONE 0x0000 /* Don't care */ #define NOTIFY_OK 0x0001 /* Suits me */ -- cgit v1.2.3