forked from luck/tmp_suning_uos_patched
clocksource: Cleanup clocksource selection
If a non high-resolution clocksource is first set as override clock and then registered it becomes active even if the system is in one-shot mode. Move the override check from sysfs_override_clocksource to the clocksource selection. That fixes the bug and simplifies the code. The check in clocksource_register for double registration of the same clocksource is removed without replacement. To find the initial clocksource a new weak function in jiffies.c is defined that returns the jiffies clocksource. The architecture code can then override the weak function with a more suitable clocksource, e.g. the TOD clock on s390. [ tglx: Folded in a fix from John Stultz ] Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Acked-by: John Stultz <johnstul@us.ibm.com> Cc: Daniel Walker <dwalker@fifo99.com> LKML-Reference: <20090814134808.388024160@de.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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1be3967948
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f1b82746c1
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@ -205,6 +205,10 @@ static struct clocksource clocksource_tod = {
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.flags = CLOCK_SOURCE_IS_CONTINUOUS,
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};
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struct clocksource * __init clocksource_default_clock(void)
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{
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return &clocksource_tod;
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}
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void update_vsyscall(struct timespec *wall_time, struct clocksource *clock)
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{
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@ -14,6 +14,7 @@
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#include <linux/list.h>
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#include <linux/cache.h>
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#include <linux/timer.h>
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#include <linux/init.h>
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#include <asm/div64.h>
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#include <asm/io.h>
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@ -322,6 +323,7 @@ extern void clocksource_touch_watchdog(void);
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extern struct clocksource* clocksource_get_next(void);
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extern void clocksource_change_rating(struct clocksource *cs, int rating);
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extern void clocksource_resume(void);
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extern struct clocksource * __init __weak clocksource_default_clock(void);
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#ifdef CONFIG_GENERIC_TIME_VSYSCALL
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extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
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@ -21,7 +21,6 @@
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*
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* TODO WishList:
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* o Allow clocksource drivers to be unregistered
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* o get rid of clocksource_jiffies extern
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*/
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#include <linux/clocksource.h>
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@ -107,12 +106,9 @@ u64 timecounter_cyc2time(struct timecounter *tc,
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}
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EXPORT_SYMBOL(timecounter_cyc2time);
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/* XXX - Would like a better way for initializing curr_clocksource */
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extern struct clocksource clocksource_jiffies;
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/*[Clocksource internal variables]---------
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* curr_clocksource:
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* currently selected clocksource. Initialized to clocksource_jiffies.
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* currently selected clocksource.
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* next_clocksource:
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* pending next selected clocksource.
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* clocksource_list:
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@ -123,9 +119,8 @@ extern struct clocksource clocksource_jiffies;
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* override_name:
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* Name of the user-specified clocksource.
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*/
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static struct clocksource *curr_clocksource = &clocksource_jiffies;
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static struct clocksource *curr_clocksource;
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static struct clocksource *next_clocksource;
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static struct clocksource *clocksource_override;
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static LIST_HEAD(clocksource_list);
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static DEFINE_SPINLOCK(clocksource_lock);
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static char override_name[32];
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@ -320,6 +315,7 @@ void clocksource_touch_watchdog(void)
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clocksource_resume_watchdog();
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}
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#ifdef CONFIG_GENERIC_TIME
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/**
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* clocksource_get_next - Returns the selected clocksource
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*
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@ -339,56 +335,65 @@ struct clocksource *clocksource_get_next(void)
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}
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/**
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* select_clocksource - Selects the best registered clocksource.
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* clocksource_select - Select the best clocksource available
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*
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* Private function. Must hold clocksource_lock when called.
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*
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* Select the clocksource with the best rating, or the clocksource,
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* which is selected by userspace override.
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*/
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static struct clocksource *select_clocksource(void)
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static void clocksource_select(void)
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{
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struct clocksource *next;
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struct clocksource *best, *cs;
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if (list_empty(&clocksource_list))
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return NULL;
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if (clocksource_override)
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next = clocksource_override;
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else
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next = list_entry(clocksource_list.next, struct clocksource,
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list);
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if (next == curr_clocksource)
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return NULL;
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return next;
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return;
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/* First clocksource on the list has the best rating. */
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best = list_first_entry(&clocksource_list, struct clocksource, list);
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/* Check for the override clocksource. */
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list_for_each_entry(cs, &clocksource_list, list) {
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if (strcmp(cs->name, override_name) != 0)
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continue;
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/*
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* Check to make sure we don't switch to a non-highres
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* capable clocksource if the tick code is in oneshot
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* mode (highres or nohz)
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*/
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if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
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tick_oneshot_mode_active()) {
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/* Override clocksource cannot be used. */
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printk(KERN_WARNING "Override clocksource %s is not "
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"HRT compatible. Cannot switch while in "
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"HRT/NOHZ mode\n", cs->name);
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override_name[0] = 0;
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} else
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/* Override clocksource can be used. */
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best = cs;
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break;
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}
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if (curr_clocksource != best)
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next_clocksource = best;
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}
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#else /* CONFIG_GENERIC_TIME */
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static void clocksource_select(void) { }
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#endif
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/*
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* Enqueue the clocksource sorted by rating
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*/
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static int clocksource_enqueue(struct clocksource *c)
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static void clocksource_enqueue(struct clocksource *cs)
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{
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struct list_head *tmp, *entry = &clocksource_list;
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struct list_head *entry = &clocksource_list;
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struct clocksource *tmp;
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list_for_each(tmp, &clocksource_list) {
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struct clocksource *cs;
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cs = list_entry(tmp, struct clocksource, list);
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if (cs == c)
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return -EBUSY;
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list_for_each_entry(tmp, &clocksource_list, list)
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/* Keep track of the place, where to insert */
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if (cs->rating >= c->rating)
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entry = tmp;
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}
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list_add(&c->list, entry);
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if (strlen(c->name) == strlen(override_name) &&
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!strcmp(c->name, override_name))
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clocksource_override = c;
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return 0;
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if (tmp->rating >= cs->rating)
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entry = &tmp->list;
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list_add(&cs->list, entry);
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}
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/**
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@ -397,19 +402,16 @@ static int clocksource_enqueue(struct clocksource *c)
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*
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* Returns -EBUSY if registration fails, zero otherwise.
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*/
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int clocksource_register(struct clocksource *c)
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int clocksource_register(struct clocksource *cs)
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{
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unsigned long flags;
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int ret;
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spin_lock_irqsave(&clocksource_lock, flags);
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ret = clocksource_enqueue(c);
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if (!ret)
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next_clocksource = select_clocksource();
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clocksource_enqueue(cs);
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clocksource_select();
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spin_unlock_irqrestore(&clocksource_lock, flags);
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if (!ret)
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clocksource_check_watchdog(c);
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return ret;
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clocksource_check_watchdog(cs);
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return 0;
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}
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EXPORT_SYMBOL(clocksource_register);
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@ -425,7 +427,7 @@ void clocksource_change_rating(struct clocksource *cs, int rating)
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list_del(&cs->list);
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cs->rating = rating;
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clocksource_enqueue(cs);
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next_clocksource = select_clocksource();
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clocksource_select();
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spin_unlock_irqrestore(&clocksource_lock, flags);
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}
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@ -438,9 +440,7 @@ void clocksource_unregister(struct clocksource *cs)
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spin_lock_irqsave(&clocksource_lock, flags);
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list_del(&cs->list);
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if (clocksource_override == cs)
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clocksource_override = NULL;
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next_clocksource = select_clocksource();
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clocksource_select();
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spin_unlock_irqrestore(&clocksource_lock, flags);
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}
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@ -478,9 +478,7 @@ static ssize_t sysfs_override_clocksource(struct sys_device *dev,
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struct sysdev_attribute *attr,
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const char *buf, size_t count)
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{
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struct clocksource *ovr = NULL;
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size_t ret = count;
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int len;
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/* strings from sysfs write are not 0 terminated! */
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if (count >= sizeof(override_name))
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@ -495,37 +493,7 @@ static ssize_t sysfs_override_clocksource(struct sys_device *dev,
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if (count > 0)
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memcpy(override_name, buf, count);
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override_name[count] = 0;
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len = strlen(override_name);
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if (len) {
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struct clocksource *cs;
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ovr = clocksource_override;
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/* try to select it: */
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list_for_each_entry(cs, &clocksource_list, list) {
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if (strlen(cs->name) == len &&
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!strcmp(cs->name, override_name))
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ovr = cs;
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}
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}
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/*
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* Check to make sure we don't switch to a non-highres capable
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* clocksource if the tick code is in oneshot mode (highres or nohz)
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*/
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if (tick_oneshot_mode_active() && ovr &&
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!(ovr->flags & CLOCK_SOURCE_VALID_FOR_HRES)) {
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printk(KERN_WARNING "%s clocksource is not HRT compatible. "
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"Cannot switch while in HRT/NOHZ mode\n", ovr->name);
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ovr = NULL;
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override_name[0] = 0;
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}
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/* Reselect, when the override name has changed */
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if (ovr != clocksource_override) {
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clocksource_override = ovr;
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next_clocksource = select_clocksource();
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}
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clocksource_select();
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spin_unlock_irq(&clocksource_lock);
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@ -61,7 +61,6 @@ struct clocksource clocksource_jiffies = {
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.read = jiffies_read,
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.mask = 0xffffffff, /*32bits*/
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.mult = NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */
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.mult_orig = NSEC_PER_JIFFY << JIFFIES_SHIFT,
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.shift = JIFFIES_SHIFT,
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};
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@ -71,3 +70,8 @@ static int __init init_jiffies_clocksource(void)
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}
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core_initcall(init_jiffies_clocksource);
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struct clocksource * __init __weak clocksource_default_clock(void)
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{
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return &clocksource_jiffies;
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}
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@ -269,7 +269,7 @@ static void change_clocksource(void)
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new = clocksource_get_next();
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if (clock == new)
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if (!new || clock == new)
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return;
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clocksource_forward_now();
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@ -446,7 +446,7 @@ void __init timekeeping_init(void)
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ntp_init();
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clock = clocksource_get_next();
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clock = clocksource_default_clock();
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if (clock->enable)
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clock->enable(clock);
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/* set mult_orig on enable */
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