2006-10-06 18:58:43

by Daniel Walker

Subject: [PATCH 06/10] -mm: clocksource: add block notifier

Adds a call back interface for register/rating change
events.

Signed-Off-By: Daniel Walker <[email protected]>

---
include/linux/clocksource.h | 8 ++++++++
kernel/time/clocksource.c | 19 ++++++++++++++++++-
kernel/timer.c | 12 ++++++++++++
3 files changed, 38 insertions(+), 1 deletion(-)

Index: linux-2.6.18/include/linux/clocksource.h
===================================================================
--- linux-2.6.18.orig/include/linux/clocksource.h
+++ linux-2.6.18/include/linux/clocksource.h
@@ -14,6 +14,7 @@
#include <linux/list.h>
#include <linux/plist.h>
#include <linux/sysdev.h>
+#include <linux/notifier.h>
#include <asm/div64.h>
#include <asm/io.h>

@@ -26,6 +27,12 @@ typedef u64 cycle_t;
*/
extern struct clocksource clocksource_jiffies;

+/*
+ * Block notifier flags.
+ */
+#define CLOCKSOURCE_NOTIFY_REGISTER 1
+#define CLOCKSOURCE_NOTIFY_RATING 2
+
/**
* struct clocksource - hardware abstraction for a free running counter
* Provides mostly state-free accessors to the underlying hardware.
@@ -205,6 +212,7 @@ static inline void clocksource_calculate


/* used to install a new clocksource */
+extern int clocksource_notifier_register(struct notifier_block*);
extern int clocksource_sysfs_register(struct sysdev_attribute*);
extern void clocksource_sysfs_unregister(struct sysdev_attribute*);
extern int clocksource_register(struct clocksource*);
Index: linux-2.6.18/kernel/time/clocksource.c
===================================================================
--- linux-2.6.18.orig/kernel/time/clocksource.c
+++ linux-2.6.18/kernel/time/clocksource.c
@@ -39,6 +39,18 @@
static __read_mostly
struct list_head clocksource_list = LIST_HEAD_INIT(clocksource_list);
static DEFINE_SPINLOCK(clocksource_lock);
+static ATOMIC_NOTIFIER_HEAD(clocksource_list_notifier);
+
+/**
+ * clocksource_notifier_register - Registers a list change notifier
+ * @nb: pointer to a notifier block
+ *
+ * Returns zero always.
+ */
+int clocksource_notifier_register(struct notifier_block *nb)
+{
+ return atomic_notifier_chain_register(&clocksource_list_notifier, nb);
+}

/**
* __is_registered - Returns a clocksource if it's registered
@@ -139,6 +151,9 @@ int clocksource_register(struct clocksou
__sorted_list_add(c);
}
spin_unlock_irqrestore(&clocksource_lock, flags);
+
+ atomic_notifier_call_chain(&clocksource_list_notifier,
+ CLOCKSOURCE_NOTIFY_REGISTER, c);
return ret;
}
EXPORT_SYMBOL(clocksource_register);
@@ -165,7 +180,9 @@ void clocksource_rating_change(struct cl
list_del_init(&c->list);
__sorted_list_add(c);

- /* XXX: Add block notifier to signal new rating */
+ atomic_notifier_call_chain(&clocksource_list_notifier,
+ CLOCKSOURCE_NOTIFY_RATING, c);
+
spin_unlock_irqrestore(&clocksource_lock, flags);
}
EXPORT_SYMBOL(clocksource_rating_change);
Index: linux-2.6.18/kernel/timer.c
===================================================================
--- linux-2.6.18.orig/kernel/timer.c
+++ linux-2.6.18/kernel/timer.c
@@ -819,6 +819,17 @@ static int __init boot_override_clocksou
}
__setup("timeofday_clocksource=", boot_override_clocksource);

+static int
+clocksource_callback(struct notifier_block *nb, unsigned long op, void *c)
+{
+ atomic_inc(&clock_check);
+ return 0;
+}
+
+static struct notifier_block clocksource_nb = {
+ .notifier_call = clocksource_callback,
+};
+
#else
#define change_clocksource(x) do { } while(0)
#endif
@@ -912,6 +923,7 @@ static int __init timekeeping_init_devic

#ifdef CONFIG_GENERIC_TIME
clocksource_sysfs_register(&attr_timeofday_clocksource);
+ clocksource_notifier_register(&clocksource_nb);

/*
* All the clocks should be registered at this point,

--

2006-10-09 19:45:18

by john stultz

Subject: Re: [PATCH 06/10] -mm: clocksource: add block notifier

On Fri, 2006-10-06 at 11:54 -0700, Daniel Walker wrote:
> plain text document attachment
> (clocksource_add_block_notify_on_new_clock.patch)
> Adds a call back interface for register/rating change
> events.
>
> Signed-Off-By: Daniel Walker <[email protected]>

This one looks interesting, but I'm not sure if we yet have the use-case
really needed to implement notifier infrastructure (taking the comments
from my last discussion). I don't really have any criticism with the
code, I just worry it might be over-doing it.

Maybe it would be more persuasive if it went together with the first
users of it, rather then as a independent infrastructure buildup patch.

thanks
-john