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 <akpm@osdl.org> Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> Signed-off-by: Michal Piotrowski <michal.k.k.piotrowski@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Gautham R Shenoy
Linus Torvalds
parent
7c9cb38302
commit
6f7cc11aa6
2 changed files with 105 additions and 37 deletions
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@ -112,32 +112,40 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
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#ifdef __KERNEL__
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extern int atomic_notifier_chain_register(struct atomic_notifier_head *,
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struct notifier_block *);
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extern int blocking_notifier_chain_register(struct blocking_notifier_head *,
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struct notifier_block *);
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extern int raw_notifier_chain_register(struct raw_notifier_head *,
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struct notifier_block *);
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extern int srcu_notifier_chain_register(struct srcu_notifier_head *,
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struct notifier_block *);
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extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
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struct notifier_block *nb);
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extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
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struct notifier_block *nb);
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extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
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struct notifier_block *nb);
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extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
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struct notifier_block *nb);
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extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *,
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struct notifier_block *);
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extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *,
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struct notifier_block *);
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extern int raw_notifier_chain_unregister(struct raw_notifier_head *,
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struct notifier_block *);
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extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *,
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struct notifier_block *);
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extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
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struct notifier_block *nb);
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extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
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struct notifier_block *nb);
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extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
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struct notifier_block *nb);
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extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
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struct notifier_block *nb);
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extern int atomic_notifier_call_chain(struct atomic_notifier_head *,
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extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
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unsigned long val, void *v);
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extern int blocking_notifier_call_chain(struct blocking_notifier_head *,
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extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
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unsigned long val, void *v, int nr_to_call, int *nr_calls);
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extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
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unsigned long val, void *v);
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extern int raw_notifier_call_chain(struct raw_notifier_head *,
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extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
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unsigned long val, void *v, int nr_to_call, int *nr_calls);
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extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
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unsigned long val, void *v);
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extern int srcu_notifier_call_chain(struct srcu_notifier_head *,
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extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
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unsigned long val, void *v, int nr_to_call, int *nr_calls);
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extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
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unsigned long val, void *v);
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extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
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unsigned long val, void *v, int nr_to_call, int *nr_calls);
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#define NOTIFY_DONE 0x0000 /* Don't care */
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#define NOTIFY_OK 0x0001 /* Suits me */
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94
kernel/sys.c
94
kernel/sys.c
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@ -134,19 +134,39 @@ static int notifier_chain_unregister(struct notifier_block **nl,
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return -ENOENT;
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}
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/**
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* notifier_call_chain - Informs the registered notifiers about an event.
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* @nl: Pointer to head of the blocking notifier chain
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* @val: Value passed unmodified to notifier function
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* @v: Pointer passed unmodified to notifier function
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* @nr_to_call: Number of notifier functions to be called. Don't care
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* value of this parameter is -1.
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* @nr_calls: Records the number of notifications sent. Don't care
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* value of this field is NULL.
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* @returns: notifier_call_chain returns the value returned by the
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* last notifier function called.
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*/
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static int __kprobes notifier_call_chain(struct notifier_block **nl,
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unsigned long val, void *v)
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unsigned long val, void *v,
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int nr_to_call, int *nr_calls)
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{
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int ret = NOTIFY_DONE;
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struct notifier_block *nb, *next_nb;
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nb = rcu_dereference(*nl);
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while (nb) {
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while (nb && nr_to_call) {
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next_nb = rcu_dereference(nb->next);
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ret = nb->notifier_call(nb, val, v);
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if (nr_calls)
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(*nr_calls)++;
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if ((ret & NOTIFY_STOP_MASK) == NOTIFY_STOP_MASK)
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break;
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nb = next_nb;
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nr_to_call--;
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}
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return ret;
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}
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@ -205,10 +225,12 @@ int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
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EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
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/**
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* atomic_notifier_call_chain - Call functions in an atomic notifier chain
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* __atomic_notifier_call_chain - Call functions in an atomic notifier chain
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* @nh: Pointer to head of the atomic notifier chain
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* @val: Value passed unmodified to notifier function
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* @v: Pointer passed unmodified to notifier function
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* @nr_to_call: See the comment for notifier_call_chain.
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* @nr_calls: See the comment for notifier_call_chain.
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*
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* Calls each function in a notifier chain in turn. The functions
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* run in an atomic context, so they must not block.
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@ -222,19 +244,27 @@ EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
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* of the last notifier function called.
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*/
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int __kprobes atomic_notifier_call_chain(struct atomic_notifier_head *nh,
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unsigned long val, void *v)
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int __kprobes __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
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unsigned long val, void *v,
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int nr_to_call, int *nr_calls)
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{
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int ret;
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rcu_read_lock();
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ret = notifier_call_chain(&nh->head, val, v);
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ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
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rcu_read_unlock();
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return ret;
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}
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EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
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EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);
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int __kprobes atomic_notifier_call_chain(struct atomic_notifier_head *nh,
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unsigned long val, void *v)
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{
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return __atomic_notifier_call_chain(nh, val, v, -1, NULL);
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}
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EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
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/*
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* Blocking notifier chain routines. All access to the chain is
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* synchronized by an rwsem.
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@ -304,10 +334,12 @@ int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
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EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
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/**
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* blocking_notifier_call_chain - Call functions in a blocking notifier chain
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* __blocking_notifier_call_chain - Call functions in a blocking notifier chain
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* @nh: Pointer to head of the blocking notifier chain
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* @val: Value passed unmodified to notifier function
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* @v: Pointer passed unmodified to notifier function
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* @nr_to_call: See comment for notifier_call_chain.
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* @nr_calls: See comment for notifier_call_chain.
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*
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* Calls each function in a notifier chain in turn. The functions
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* run in a process context, so they are allowed to block.
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@ -320,8 +352,9 @@ EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
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* of the last notifier function called.
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*/
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int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
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unsigned long val, void *v)
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int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
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unsigned long val, void *v,
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int nr_to_call, int *nr_calls)
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{
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int ret = NOTIFY_DONE;
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@ -332,12 +365,19 @@ int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
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*/
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if (rcu_dereference(nh->head)) {
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down_read(&nh->rwsem);
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ret = notifier_call_chain(&nh->head, val, v);
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ret = notifier_call_chain(&nh->head, val, v, nr_to_call,
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nr_calls);
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up_read(&nh->rwsem);
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}
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return ret;
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}
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EXPORT_SYMBOL_GPL(__blocking_notifier_call_chain);
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int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
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unsigned long val, void *v)
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{
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return __blocking_notifier_call_chain(nh, val, v, -1, NULL);
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}
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EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
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/*
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@ -383,10 +423,12 @@ int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
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EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
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/**
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* raw_notifier_call_chain - Call functions in a raw notifier chain
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* __raw_notifier_call_chain - Call functions in a raw notifier chain
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* @nh: Pointer to head of the raw notifier chain
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* @val: Value passed unmodified to notifier function
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* @v: Pointer passed unmodified to notifier function
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* @nr_to_call: See comment for notifier_call_chain.
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* @nr_calls: See comment for notifier_call_chain
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*
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* Calls each function in a notifier chain in turn. The functions
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* run in an undefined context.
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@ -400,10 +442,19 @@ EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
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* of the last notifier function called.
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*/
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int __raw_notifier_call_chain(struct raw_notifier_head *nh,
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unsigned long val, void *v,
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int nr_to_call, int *nr_calls)
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{
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return notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
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}
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EXPORT_SYMBOL_GPL(__raw_notifier_call_chain);
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int raw_notifier_call_chain(struct raw_notifier_head *nh,
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unsigned long val, void *v)
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{
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return notifier_call_chain(&nh->head, val, v);
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return __raw_notifier_call_chain(nh, val, v, -1, NULL);
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}
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EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
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@ -478,10 +529,12 @@ int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
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EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister);
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/**
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* srcu_notifier_call_chain - Call functions in an SRCU notifier chain
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* __srcu_notifier_call_chain - Call functions in an SRCU notifier chain
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* @nh: Pointer to head of the SRCU notifier chain
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* @val: Value passed unmodified to notifier function
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* @v: Pointer passed unmodified to notifier function
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* @nr_to_call: See comment for notifier_call_chain.
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* @nr_calls: See comment for notifier_call_chain
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*
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* Calls each function in a notifier chain in turn. The functions
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* run in a process context, so they are allowed to block.
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@ -494,18 +547,25 @@ EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister);
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* of the last notifier function called.
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*/
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int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
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unsigned long val, void *v)
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int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
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unsigned long val, void *v,
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int nr_to_call, int *nr_calls)
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{
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int ret;
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int idx;
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idx = srcu_read_lock(&nh->srcu);
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ret = notifier_call_chain(&nh->head, val, v);
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ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
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srcu_read_unlock(&nh->srcu, idx);
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return ret;
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}
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EXPORT_SYMBOL_GPL(__srcu_notifier_call_chain);
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int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
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unsigned long val, void *v)
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{
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return __srcu_notifier_call_chain(nh, val, v, -1, NULL);
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}
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EXPORT_SYMBOL_GPL(srcu_notifier_call_chain);
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/**
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