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Subject[PATCH 18/20] clockevents: Make tick handover explicit
Date
From: Thomas Gleixner <tglx@linutronix.de>

clockevents_notify() is a leftover from the early design of the
clockevents facility. It's really not a notification mechanism, it's a
multiplex call. We are way better off to have explicit calls instead of this
monstrosity.

Split out the tick_handover call and invoke it explicitely from the
hotplug code. Temporary solution will be cleaned up in later patches.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[ rjw: Rebase ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
include/linux/clockchips.h | 1 -
include/linux/tick.h | 2 ++
kernel/cpu.c | 3 +++
kernel/time/clockevents.c | 4 ----
kernel/time/hrtimer.c | 4 ----
kernel/time/tick-common.c | 9 ++++++---
kernel/time/tick-internal.h | 1 -
7 files changed, 11 insertions(+), 13 deletions(-)

Index: linux-pm/include/linux/clockchips.h
===================================================================
--- linux-pm.orig/include/linux/clockchips.h
+++ linux-pm/include/linux/clockchips.h
@@ -11,7 +11,6 @@
/* Clock event notification values */
enum clock_event_nofitiers {
CLOCK_EVT_NOTIFY_ADD,
- CLOCK_EVT_NOTIFY_CPU_DYING,
CLOCK_EVT_NOTIFY_CPU_DEAD,
};

Index: linux-pm/include/linux/tick.h
===================================================================
--- linux-pm.orig/include/linux/tick.h
+++ linux-pm/include/linux/tick.h
@@ -19,12 +19,14 @@ extern void tick_unfreeze(void);
extern void tick_suspend_local(void);
/* Should be core only, but XEN resume magic and ARM BL switcher require it */
extern void tick_resume_local(void);
+extern void tick_handover_do_timer(void);
#else /* CONFIG_GENERIC_CLOCKEVENTS */
static inline void tick_init(void) { }
static inline void tick_freeze(void) { }
static inline void tick_unfreeze(void) { }
static inline void tick_suspend_local(void) { }
static inline void tick_resume_local(void) { }
+static inline void tick_handover_do_timer(void) { }
#endif /* !CONFIG_GENERIC_CLOCKEVENTS */

#ifdef CONFIG_TICK_ONESHOT
Index: linux-pm/kernel/cpu.c
===================================================================
--- linux-pm.orig/kernel/cpu.c
+++ linux-pm/kernel/cpu.c
@@ -20,6 +20,7 @@
#include <linux/gfp.h>
#include <linux/suspend.h>
#include <linux/lockdep.h>
+#include <linux/tick.h>
#include <trace/events/power.h>

#include "smpboot.h"
@@ -338,6 +339,8 @@ static int __ref take_cpu_down(void *_pa
return err;

cpu_notify(CPU_DYING | param->mod, param->hcpu);
+ /* Give up timekeeping duties */
+ tick_handover_do_timer();
/* Park the stopper thread */
kthread_park(current);
return 0;
Index: linux-pm/kernel/time/clockevents.c
===================================================================
--- linux-pm.orig/kernel/time/clockevents.c
+++ linux-pm/kernel/time/clockevents.c
@@ -655,10 +655,6 @@ int clockevents_notify(unsigned long rea
raw_spin_lock_irqsave(&clockevents_lock, flags);

switch (reason) {
- case CLOCK_EVT_NOTIFY_CPU_DYING:
- tick_handover_do_timer(arg);
- break;
-
case CLOCK_EVT_NOTIFY_CPU_DEAD:
tick_shutdown_broadcast_oneshot(arg);
tick_shutdown_broadcast(arg);
Index: linux-pm/kernel/time/hrtimer.c
===================================================================
--- linux-pm.orig/kernel/time/hrtimer.c
+++ linux-pm/kernel/time/hrtimer.c
@@ -1707,10 +1707,6 @@ static int hrtimer_cpu_notify(struct not
break;

#ifdef CONFIG_HOTPLUG_CPU
- case CPU_DYING:
- case CPU_DYING_FROZEN:
- clockevents_notify(CLOCK_EVT_NOTIFY_CPU_DYING, &scpu);
- break;
case CPU_DEAD:
case CPU_DEAD_FROZEN:
{
Index: linux-pm/kernel/time/tick-common.c
===================================================================
--- linux-pm.orig/kernel/time/tick-common.c
+++ linux-pm/kernel/time/tick-common.c
@@ -332,20 +332,23 @@ out_bc:
tick_install_broadcast_device(newdev);
}

+#ifdef CONFIG_HOTPLUG_CPU
/*
* Transfer the do_timer job away from a dying cpu.
*
- * Called with interrupts disabled.
+ * Called with interrupts disabled. Not locking required. If
+ * tick_do_timer_cpu is owned by this cpu, nothing can change it.
*/
-void tick_handover_do_timer(int *cpup)
+void tick_handover_do_timer(void)
{
- if (*cpup == tick_do_timer_cpu) {
+ if (tick_do_timer_cpu == smp_processor_id()) {
int cpu = cpumask_first(cpu_online_mask);

tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
TICK_DO_TIMER_NONE;
}
}
+#endif

/*
* Shutdown an event device on a given cpu:
Index: linux-pm/kernel/time/tick-internal.h
===================================================================
--- linux-pm.orig/kernel/time/tick-internal.h
+++ linux-pm/kernel/time/tick-internal.h
@@ -20,7 +20,6 @@ extern int tick_do_timer_cpu __read_most
extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast);
extern void tick_handle_periodic(struct clock_event_device *dev);
extern void tick_check_new_device(struct clock_event_device *dev);
-extern void tick_handover_do_timer(int *cpup);
extern void tick_shutdown(unsigned int *cpup);
extern void tick_suspend(void);
extern void tick_resume(void);


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