Commit 47a1b796 authored by John Stultz's avatar John Stultz
Browse files

tick/timekeeping: Call update_wall_time outside the jiffies lock 



Since the xtime lock was split into the timekeeping lock and
the jiffies lock, we no longer need to call update_wall_time()
while holding the jiffies lock.

Thus, this patch splits update_wall_time() out from do_timer().

This allows us to get away from calling clock_was_set_delayed()
in update_wall_time() and instead use the standard clock_was_set()
call that previously would deadlock, as it causes the jiffies lock
to be acquired.

Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent 6fdda9a9

kernel/time/tick-common.c

+1 −0
Original line number Diff line number Diff line
@@ -70,6 +70,7 @@ static void tick_periodic(int cpu) 


		do_timer(1);

		write_sequnlock(&jiffies_lock);

		update_wall_time();

	}



	update_process_times(user_mode(get_irq_regs()));

kernel/time/tick-internal.h

+1 −0
Original line number Diff line number Diff line
@@ -155,3 +155,4 @@ static inline int tick_device_is_functional(struct clock_event_device *dev) 
#endif



extern void do_timer(unsigned long ticks);

extern void update_wall_time(void);

kernel/time/tick-sched.c

+1 −0
Original line number Diff line number Diff line
@@ -86,6 +86,7 @@ static void tick_do_update_jiffies64(ktime_t now) 
		tick_next_period = ktime_add(last_jiffies_update, tick_period);

	}

	write_sequnlock(&jiffies_lock);

	update_wall_time();

}



/*

kernel/time/timekeeping.c

+4 −15
Original line number Diff line number Diff line
@@ -1360,7 +1360,7 @@ static inline void old_vsyscall_fixup(struct timekeeper *tk) 
 * update_wall_time - Uses the current clocksource to increment the wall time

 *

 */

static void update_wall_time(void)

void update_wall_time(void)

{

	struct clocksource *clock;

	struct timekeeper *real_tk = &timekeeper;
@@ -1441,19 +1441,8 @@ static void update_wall_time(void) 
	write_seqcount_end(&timekeeper_seq);

out:

	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);

	if (clock_was_set) {

		/*

		 * XXX -  I'd rather we just call clock_was_set(), but

		 * since we're currently holding the jiffies lock, calling

		 * clock_was_set would trigger an ipi which would then grab

		 * the jiffies lock and we'd deadlock. :(

		 * The right solution should probably be droping

		 * the jiffies lock before calling update_wall_time

		 * but that requires some rework of the tick sched

		 * code.

		 */

		clock_was_set_delayed();

	}

	if (clock_set)

		clock_was_set();

}



/**
@@ -1598,7 +1587,6 @@ struct timespec get_monotonic_coarse(void) 
void do_timer(unsigned long ticks)

{

	jiffies_64 += ticks;

	update_wall_time();

	calc_global_load(ticks);

}
@@ -1756,4 +1744,5 @@ void xtime_update(unsigned long ticks) 
	write_seqlock(&jiffies_lock);

	do_timer(ticks);

	write_sequnlock(&jiffies_lock);

	update_wall_time();

}

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