[PATCH 3/7] time: Rework debugging variables so they aren't global

John Stultz
2015-05-20T17:22:15Z

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 differnet 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: John Stultz <john.stultz@linaro.org>
---
include/linux/timekeeper_internal.h | 15 +++++++++++++++
kernel/time/timekeeping.c | 33 +++++++++++----------------------
2 files changed, 26 insertions(+), 22 deletions(-)

diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h
index 6f8276a..35007b2 100644
--- a/include/linux/timekeeper_internal.h
+++ b/include/linux/timekeeper_internal.h
@@ -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 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
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 85d3763..2f10b65 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -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;
}

--
1.9.1