Commit f55a6faa authored by John Stultz's avatar John Stultz Committed by Thomas Gleixner
Browse files

hrtimer: Provide clock_was_set_delayed() 



clock_was_set() cannot be called from hard interrupt context because
it calls on_each_cpu().

For fixing the widely reported leap seconds issue it is necessary to
call it from hard interrupt context, i.e. the timer tick code, which
does the timekeeping updates.

Provide a new function which denotes it in the hrtimer cpu base
structure of the cpu on which it is called and raise the hrtimer
softirq. We then execute the clock_was_set() notificiation from
softirq context in run_hrtimer_softirq(). The hrtimer softirq is
rarely used, so polling the flag there is not a performance issue.

[ tglx: Made it depend on CONFIG_HIGH_RES_TIMERS. We really should get
  rid of all this ifdeffery ASAP ]

Signed-off-by: default avatarJohn Stultz <johnstul@us.ibm.com>
Reported-by: default avatarJan Engelhardt <jengelh@inai.de>
Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: default avatarPrarit Bhargava <prarit@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1341960205-56738-2-git-send-email-johnstul@us.ibm.com


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 055c9fa8

include/linux/hrtimer.h

+8 −1
Original line number Diff line number Diff line
@@ -165,6 +165,7 @@ enum hrtimer_base_type { 
 * @lock:		lock protecting the base and associated clock bases

 *			and timers

 * @active_bases:	Bitfield to mark bases with active timers

 * @clock_was_set:	Indicates that clock was set from irq context.

 * @expires_next:	absolute time of the next event which was scheduled

 *			via clock_set_next_event()

 * @hres_active:	State of high resolution mode
@@ -177,7 +178,8 @@ enum hrtimer_base_type { 
 */

struct hrtimer_cpu_base {

	raw_spinlock_t			lock;

	unsigned long			active_bases;

	unsigned int			active_bases;

	unsigned int			clock_was_set;

#ifdef CONFIG_HIGH_RES_TIMERS

	ktime_t				expires_next;

	int				hres_active;
@@ -286,6 +288,8 @@ extern void hrtimer_peek_ahead_timers(void); 
# define MONOTONIC_RES_NSEC	HIGH_RES_NSEC

# define KTIME_MONOTONIC_RES	KTIME_HIGH_RES



extern void clock_was_set_delayed(void);



#else



# define MONOTONIC_RES_NSEC	LOW_RES_NSEC
@@ -306,6 +310,9 @@ static inline int hrtimer_is_hres_active(struct hrtimer *timer) 
{

	return 0;

}



static inline void clock_was_set_delayed(void) { }



#endif



extern void clock_was_set(void);

kernel/hrtimer.c

+20 −0
Original line number Diff line number Diff line
@@ -717,6 +717,19 @@ static int hrtimer_switch_to_hres(void) 
	return 1;

}



/*

 * Called from timekeeping code to reprogramm the hrtimer interrupt

 * device. If called from the timer interrupt context we defer it to

 * softirq context.

 */

void clock_was_set_delayed(void)

{

	struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);



	cpu_base->clock_was_set = 1;

	__raise_softirq_irqoff(HRTIMER_SOFTIRQ);

}



#else



static inline int hrtimer_hres_active(void) { return 0; }
@@ -1395,6 +1408,13 @@ void hrtimer_peek_ahead_timers(void) 


static void run_hrtimer_softirq(struct softirq_action *h)

{

	struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);



	if (cpu_base->clock_was_set) {

		cpu_base->clock_was_set = 0;

		clock_was_set();

	}



	hrtimer_peek_ahead_timers();

}

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