The patch titled
Extend notifier_call_chain to count nr_calls made
has been added to the -mm tree. Its filename is
extend-notifier_call_chain-to-count-nr_calls-made.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: Extend notifier_call_chain to count nr_calls made
From: Gautham R Shenoy <ego@xxxxxxxxxx>
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.
Credit: Andrew Morton <akpm@xxxxxxxx>
Signed-off-by: Gautham R Shenoy <ego@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/linux/notifier.h | 8 +++
kernel/sys.c | 97 ++++++++++++++++++++++++++++++-------
2 files changed, 89 insertions(+), 16 deletions(-)
diff -puN include/linux/notifier.h~extend-notifier_call_chain-to-count-nr_calls-made include/linux/notifier.h
--- a/include/linux/notifier.h~extend-notifier_call_chain-to-count-nr_calls-made
+++ a/include/linux/notifier.h
@@ -132,12 +132,20 @@ extern int srcu_notifier_chain_unregiste
extern int atomic_notifier_call_chain(struct atomic_notifier_head *,
unsigned long val, void *v);
+extern int __atomic_notifier_call_chain(struct atomic_notifier_head *,
+ unsigned long val, void *v, int nr_to_call, unsigned int *nr_calls);
extern int blocking_notifier_call_chain(struct blocking_notifier_head *,
unsigned long val, void *v);
+extern int __blocking_notifier_call_chain(struct blocking_notifier_head *,
+ unsigned long val, void *v, int nr_to_call, unsigned int *nr_calls);
extern int raw_notifier_call_chain(struct raw_notifier_head *,
unsigned long val, void *v);
+extern int __raw_notifier_call_chain(struct raw_notifier_head *,
+ unsigned long val, void *v, int nr_to_call, unsigned int *nr_calls);
extern int srcu_notifier_call_chain(struct srcu_notifier_head *,
unsigned long val, void *v);
+extern int __srcu_notifier_call_chain(struct srcu_notifier_head *,
+ unsigned long val, void *v, int nr_to_call, unsigned int *nr_calls);
#define NOTIFY_DONE 0x0000 /* Don't care */
#define NOTIFY_OK 0x0001 /* Suits me */
diff -puN kernel/sys.c~extend-notifier_call_chain-to-count-nr_calls-made kernel/sys.c
--- a/kernel/sys.c~extend-notifier_call_chain-to-count-nr_calls-made
+++ a/kernel/sys.c
@@ -134,19 +134,41 @@ static int notifier_chain_unregister(str
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.
+ *
+ * RETURN VALUE: 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, unsigned 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 +227,13 @@ int atomic_notifier_chain_unregister(str
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 +247,27 @@ EXPORT_SYMBOL_GPL(atomic_notifier_chain_
* 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, unsigned 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 +337,13 @@ int blocking_notifier_chain_unregister(s
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.
@@ -320,17 +356,26 @@ EXPORT_SYMBOL_GPL(blocking_notifier_chai
* 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, unsigned int * nr_calls)
{
int ret;
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);
/*
@@ -376,10 +421,12 @@ int raw_notifier_chain_unregister(struct
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.
@@ -393,10 +440,19 @@ EXPORT_SYMBOL_GPL(raw_notifier_chain_unr
* 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, unsigned 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);
@@ -475,6 +531,8 @@ EXPORT_SYMBOL_GPL(srcu_notifier_chain_un
* @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.
@@ -487,18 +545,25 @@ EXPORT_SYMBOL_GPL(srcu_notifier_chain_un
* 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, unsigned 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);
/**
_
Patches currently in -mm which might be from ego@xxxxxxxxxx are
git-cpufreq.patch
extend-notifier_call_chain-to-count-nr_calls-made.patch
define-and-use-new-eventscpu_lock_acquire-and-cpu_lock_release.patch
define-and-use-new-eventscpu_lock_acquire-and-cpu_lock_release-fix.patch
eliminate-lock_cpu_hotplug-in-kernel-schedc.patch
handle-cpu_lock_acquire-and-cpu_lock_release-in-workqueue_cpu_callback.patch
-
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