[PATCH 1/3] time: create __get_monotonic_boottime for WARNless calls

[Lei Wen]

Since sched_clock always get stopped during suspend period, it
would make it hard to use the kernel log to compare with other
procssor generated log which running over the same machine.
[Absolutely not running linux]

So we need a way to recover the printk timestamp that including
suspend time in the old way, get_monotonic_boottime is a good
candidate, but it cannot be called after suspend process has happen.
Thus, it prevent printk to be used in every corner.

Export one warn less __get_monotonic_boottime to solve this issue.

Signed-off-by: Lei Wen <leiwen@xxxxxxxxxxx>
---
 include/linux/time.h      |  1 +
 kernel/time/timekeeping.c | 33 ++++++++++++++++++++++++++++-----
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/include/linux/time.h b/include/linux/time.h
index d5d229b..a2f5079 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -171,6 +171,7 @@ extern void getnstime_raw_and_real(struct timespec *ts_raw,
 		struct timespec *ts_real);
 extern void getboottime(struct timespec *ts);
 extern void monotonic_to_bootbased(struct timespec *ts);
+extern int __get_monotonic_boottime(struct timespec *ts);
 extern void get_monotonic_boottime(struct timespec *ts);
 
 extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 5b40279..c196111 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1465,23 +1465,22 @@ void getboottime(struct timespec *ts)
 EXPORT_SYMBOL_GPL(getboottime);
 
 /**
- * get_monotonic_boottime - Returns monotonic time since boot
+ * __get_monotonic_boottime - Returns monotonic time since boot
  * @ts:		pointer to the timespec to be set
  *
- * Returns the monotonic time since boot in a timespec.
+ * Update the monotonic time since boot in a timespec.
+ * Returns 0 on success, or -ve when suspended (timespec will be undefined).
  *
  * This is similar to CLOCK_MONTONIC/ktime_get_ts, but also
  * includes the time spent in suspend.
  */
-void get_monotonic_boottime(struct timespec *ts)
+int __get_monotonic_boottime(struct timespec *ts)
 {
 	struct timekeeper *tk = &timekeeper;
 	struct timespec tomono, sleep;
 	s64 nsec;
 	unsigned int seq;
 
-	WARN_ON(timekeeping_suspended);
-
 	do {
 		seq = read_seqcount_begin(&timekeeper_seq);
 		ts->tv_sec = tk->xtime_sec;
@@ -1494,6 +1493,30 @@ void get_monotonic_boottime(struct timespec *ts)
 	ts->tv_sec += tomono.tv_sec + sleep.tv_sec;
 	ts->tv_nsec = 0;
 	timespec_add_ns(ts, nsec + tomono.tv_nsec + sleep.tv_nsec);
+
+	/*
+	 * Do not bail out early, in case there were callers still using
+	 * the value, even in the face of the WARN_ON.
+	 */
+	if (unlikely(timekeeping_suspended))
+		return -EAGAIN;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__get_monotonic_boottime);
+
+/**
+ * get_monotonic_boottime - Returns monotonic time since boot
+ * @ts:		pointer to the timespec to be set
+ *
+ * Returns the monotonic time since boot in a timespec.
+ * (WARN if suspended)
+ *
+ * This is similar to CLOCK_MONTONIC/ktime_get_ts, but also
+ * includes the time spent in suspend.
+ */
+void get_monotonic_boottime(struct timespec *ts)
+{
+	WARN_ON(__get_monotonic_boottime(ts));
 }
 EXPORT_SYMBOL_GPL(get_monotonic_boottime);
 
-- 
1.8.3.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/