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authorGautham R Shenoy <ego@in.ibm.com>2007-05-09 02:34:02 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-09 12:30:51 -0700
commit6f7cc11aa6c7d5002e16096c7590944daece70ed (patch)
tree68a11e4b67189c44ac0f3ab579e52e134d479cf5
parent7c9cb38302e78d24e37f7d8a2ea7eed4ae5f2fa7 (diff)
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>
-rw-r--r--include/linux/notifier.h52
-rw-r--r--kernel/sys.c94
2 files changed, 107 insertions, 39 deletions
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 */
diff --git a/kernel/sys.c b/kernel/sys.c
index 8ecfe3473779..d4985df21b60 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -134,19 +134,39 @@ static int notifier_chain_unregister(struct notifier_block **nl,
return -ENOENT;
}
+/**
+ * notifier_call_chain - Informs the registered notifiers about an event.
+ * @nl: Pointer to head of the blocking notifier chain
+ * @val: Value passed unmodified to notifier function
+ * @v: Pointer passed unmodified to notifier function
+ * @nr_to_call: Number of notifier functions to be called. Don't care
+ * value of this parameter is -1.
+ * @nr_calls: Records the number of notifications sent. Don't care
+ * value of this field is NULL.
+ * @returns: notifier_call_chain returns the value returned by the
+ * last notifier function called.
+ */
+
static int __kprobes notifier_call_chain(struct notifier_block **nl,
- unsigned long val, void *v)
+ unsigned long val, void *v,
+ int nr_to_call, int *nr_calls)
{
int ret = NOTIFY_DONE;
struct notifier_block *nb, *next_nb;
nb = rcu_dereference(*nl);
- while (nb) {
+
+ while (nb && nr_to_call) {
next_nb = rcu_dereference(nb->next);
ret = nb->notifier_call(nb, val, v);
+
+ if (nr_calls)
+ (*nr_calls)++;
+
if ((ret & NOTIFY_STOP_MASK) == NOTIFY_STOP_MASK)
break;
nb = next_nb;
+ nr_to_call--;
}
return ret;
}
@@ -205,10 +225,12 @@ int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
/**
- * atomic_notifier_call_chain - Call functions in an atomic notifier chain
+ * __atomic_notifier_call_chain - Call functions in an atomic notifier chain
* @nh: Pointer to head of the atomic notifier chain
* @val: Value passed unmodified to notifier function
* @v: Pointer passed unmodified to notifier function
+ * @nr_to_call: See the comment for notifier_call_chain.
+ * @nr_calls: See the comment for notifier_call_chain.
*
* Calls each function in a notifier chain in turn. The functions
* run in an atomic context, so they must not block.
@@ -222,19 +244,27 @@ EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
* of the last notifier function called.
*/
-int __kprobes atomic_notifier_call_chain(struct atomic_notifier_head *nh,
- unsigned long val, void *v)
+int __kprobes __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
+ unsigned long val, void *v,
+ int nr_to_call, int *nr_calls)
{
int ret;
rcu_read_lock();
- ret = notifier_call_chain(&nh->head, val, v);
+ ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
rcu_read_unlock();
return ret;
}
-EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
+EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);
+
+int __kprobes atomic_notifier_call_chain(struct atomic_notifier_head *nh,
+ unsigned long val, void *v)
+{
+ return __atomic_notifier_call_chain(nh, val, v, -1, NULL);
+}
+EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
/*
* Blocking notifier chain routines. All access to the chain is
* synchronized by an rwsem.
@@ -304,10 +334,12 @@ int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
/**
- * blocking_notifier_call_chain - Call functions in a blocking notifier chain
+ * __blocking_notifier_call_chain - Call functions in a blocking notifier chain
* @nh: Pointer to head of the blocking notifier chain
* @val: Value passed unmodified to notifier function
* @v: Pointer passed unmodified to notifier function
+ * @nr_to_call: See comment for notifier_call_chain.
+ * @nr_calls: See comment for notifier_call_chain.
*
* Calls each function in a notifier chain in turn. The functions
* run in a process context, so they are allowed to block.
@@ -320,8 +352,9 @@ EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
* of the last notifier function called.
*/
-int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
- unsigned long val, void *v)
+int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
+ unsigned long val, void *v,
+ int nr_to_call, int *nr_calls)
{
int ret = NOTIFY_DONE;
@@ -332,12 +365,19 @@ int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
*/
if (rcu_dereference(nh->head)) {
down_read(&nh->rwsem);
- ret = notifier_call_chain(&nh->head, val, v);
+ ret = notifier_call_chain(&nh->head, val, v, nr_to_call,
+ nr_calls);
up_read(&nh->rwsem);
}
return ret;
}
+EXPORT_SYMBOL_GPL(__blocking_notifier_call_chain);
+int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
+ unsigned long val, void *v)
+{
+ return __blocking_notifier_call_chain(nh, val, v, -1, NULL);
+}
EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
/*
@@ -383,10 +423,12 @@ int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
/**
- * raw_notifier_call_chain - Call functions in a raw notifier chain
+ * __raw_notifier_call_chain - Call functions in a raw notifier chain
* @nh: Pointer to head of the raw notifier chain
* @val: Value passed unmodified to notifier function
* @v: Pointer passed unmodified to notifier function
+ * @nr_to_call: See comment for notifier_call_chain.
+ * @nr_calls: See comment for notifier_call_chain
*
* Calls each function in a notifier chain in turn. The functions
* run in an undefined context.
@@ -400,10 +442,19 @@ EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
* of the last notifier function called.
*/
+int __raw_notifier_call_chain(struct raw_notifier_head *nh,
+ unsigned long val, void *v,
+ int nr_to_call, int *nr_calls)
+{
+ return notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
+}
+
+EXPORT_SYMBOL_GPL(__raw_notifier_call_chain);
+
int raw_notifier_call_chain(struct raw_notifier_head *nh,
unsigned long val, void *v)
{
- return notifier_call_chain(&nh->head, val, v);
+ return __raw_notifier_call_chain(nh, val, v, -1, NULL);
}
EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
@@ -478,10 +529,12 @@ int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister);
/**
- * srcu_notifier_call_chain - Call functions in an SRCU notifier chain
+ * __srcu_notifier_call_chain - Call functions in an SRCU notifier chain
* @nh: Pointer to head of the SRCU notifier chain
* @val: Value passed unmodified to notifier function
* @v: Pointer passed unmodified to notifier function
+ * @nr_to_call: See comment for notifier_call_chain.
+ * @nr_calls: See comment for notifier_call_chain
*
* Calls each function in a notifier chain in turn. The functions
* run in a process context, so they are allowed to block.
@@ -494,18 +547,25 @@ EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister);
* of the last notifier function called.
*/
-int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
- unsigned long val, void *v)
+int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
+ unsigned long val, void *v,
+ int nr_to_call, int *nr_calls)
{
int ret;
int idx;
idx = srcu_read_lock(&nh->srcu);
- ret = notifier_call_chain(&nh->head, val, v);
+ ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
srcu_read_unlock(&nh->srcu, idx);
return ret;
}
+EXPORT_SYMBOL_GPL(__srcu_notifier_call_chain);
+int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
+ unsigned long val, void *v)
+{
+ return __srcu_notifier_call_chain(nh, val, v, -1, NULL);
+}
EXPORT_SYMBOL_GPL(srcu_notifier_call_chain);
/**

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