Commit 57d05a93 authored by John Stultz's avatar John Stultz
Browse files

time: Rework debugging variables so they aren't global 



Ingo suggested that the timekeeping debugging variables
recently added should not be global, and should be tied
to the timekeeper's read_base.

Thus this patch implements that suggestion.

This version is different from the earlier versions
as it keeps the variables in the timekeeper structure
rather then in the tkr.

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent 6374f912

include/linux/timekeeper_internal.h

+15 −0
Original line number Diff line number Diff line
@@ -61,6 +61,9 @@ struct tk_read_base { 
 *			shifted nano seconds.

 * @ntp_error_shift:	Shift conversion between clock shifted nano seconds and

 *			ntp shifted nano seconds.

 * @last_warning:	Warning ratelimiter (DEBUG_TIMEKEEPING)

 * @underflow_seen:	Underflow warning flag (DEBUG_TIMEKEEPING)

 * @overflow_seen:	Overflow warning flag (DEBUG_TIMEKEEPING)

 *

 * Note: For timespec(64) based interfaces wall_to_monotonic is what

 * we need to add to xtime (or xtime corrected for sub jiffie times)
@@ -106,6 +109,18 @@ struct timekeeper { 
	s64			ntp_error;

	u32			ntp_error_shift;

	u32			ntp_err_mult;

#ifdef CONFIG_DEBUG_TIMEKEEPING

	long			last_warning;

	/*

	 * These simple flag variables are managed

	 * without locks, which is racy, but they are

	 * ok since we don't really care about being

	 * super precise about how many events were

	 * seen, just that a problem was observed.

	 */

	int			underflow_seen;

	int			overflow_seen;

#endif

};



#ifdef CONFIG_GENERIC_TIME_VSYSCALL

kernel/time/timekeeping.c

+11 −22
Original line number Diff line number Diff line
@@ -118,18 +118,6 @@ static inline void tk_update_sleep_time(struct timekeeper *tk, ktime_t delta) 


#ifdef CONFIG_DEBUG_TIMEKEEPING

#define WARNING_FREQ (HZ*300) /* 5 minute rate-limiting */

/*

 * These simple flag variables are managed

 * without locks, which is racy, but ok since

 * we don't really care about being super

 * precise about how many events were seen,

 * just that a problem was observed.

 */

static int timekeeping_underflow_seen;

static int timekeeping_overflow_seen;



/* last_warning is only modified under the timekeeping lock */

static long timekeeping_last_warning;



static void timekeeping_check_update(struct timekeeper *tk, cycle_t offset)

{
@@ -149,29 +137,30 @@ static void timekeeping_check_update(struct timekeeper *tk, cycle_t offset) 
		}

	}



	if (timekeeping_underflow_seen) {

		if (jiffies - timekeeping_last_warning > WARNING_FREQ) {

	if (tk->underflow_seen) {

		if (jiffies - tk->last_warning > WARNING_FREQ) {

			printk_deferred("WARNING: Underflow in clocksource '%s' observed, time update ignored.\n", name);

			printk_deferred("         Please report this, consider using a different clocksource, if possible.\n");

			printk_deferred("         Your kernel is probably still fine.\n");

			timekeeping_last_warning = jiffies;

			tk->last_warning = jiffies;

		}

		timekeeping_underflow_seen = 0;

		tk->underflow_seen = 0;

	}



	if (timekeeping_overflow_seen) {

		if (jiffies - timekeeping_last_warning > WARNING_FREQ) {

	if (tk->overflow_seen) {

		if (jiffies - tk->last_warning > WARNING_FREQ) {

			printk_deferred("WARNING: Overflow in clocksource '%s' observed, time update capped.\n", name);

			printk_deferred("         Please report this, consider using a different clocksource, if possible.\n");

			printk_deferred("         Your kernel is probably still fine.\n");

			timekeeping_last_warning = jiffies;

			tk->last_warning = jiffies;

		}

		timekeeping_overflow_seen = 0;

		tk->overflow_seen = 0;

	}

}



static inline cycle_t timekeeping_get_delta(struct tk_read_base *tkr)

{

	struct timekeeper *tk = &tk_core.timekeeper;

	cycle_t now, last, mask, max, delta;

	unsigned int seq;
@@ -197,13 +186,13 @@ static inline cycle_t timekeeping_get_delta(struct tk_read_base *tkr) 
	 * mask-relative negative values.

	 */

	if (unlikely((~delta & mask) < (mask >> 3))) {

		timekeeping_underflow_seen = 1;

		tk->underflow_seen = 1;

		delta = 0;

	}



	/* Cap delta value to the max_cycles values to avoid mult overflows */

	if (unlikely(delta > max)) {

		timekeeping_overflow_seen = 1;

		tk->overflow_seen = 1;

		delta = tkr->clock->max_cycles;

	}

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