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Subject[PATCH 1/3 RESEND] RFC: timekeeping: introduce flag systime_was_set
Date
In order to let an RTC set the time at boot without the problem that a
second RTC overwrites it, the flag systime_was_set is introduced.

systime_was_set will be true, if a persistent clock sets the time at boot,
or if do_settimeofday() is called (e.g. by the RTC subsystem or userspace).

Signed-off-by: Alexander Holler <holler@ahsoftware.de>
---
include/linux/time.h | 6 ++++++
kernel/time/timekeeping.c | 10 +++++++++-
2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/linux/time.h b/include/linux/time.h
index d5d229b..888280f 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -129,6 +129,12 @@ extern int update_persistent_clock(struct timespec now);
void timekeeping_init(void);
extern int timekeeping_suspended;

+/*
+ * Will be true if the system time was set at least once by
+ * a persistent clock, RTC or userspace.
+ */
+extern bool systime_was_set;
+
unsigned long get_seconds(void);
struct timespec current_kernel_time(void);
struct timespec __current_kernel_time(void); /* does not take xtime_lock */
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 98cd470..07f151f 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -37,6 +37,9 @@ int __read_mostly timekeeping_suspended;
/* Flag for if there is a persistent clock on this platform */
bool __read_mostly persistent_clock_exist = false;

+/* Flag for if the system time was set at least once */
+bool __read_mostly systime_was_set;
+
static inline void tk_normalize_xtime(struct timekeeper *tk)
{
while (tk->xtime_nsec >= ((u64)NSEC_PER_SEC << tk->shift)) {
@@ -498,6 +501,9 @@ int do_settimeofday(const struct timespec *tv)
raw_spin_lock_irqsave(&timekeeper_lock, flags);
write_seqcount_begin(&timekeeper_seq);

+ systime_was_set = true;
+
+
timekeeping_forward_now(tk);

xt = tk_xtime(tk);
@@ -781,8 +787,10 @@ void __init timekeeping_init(void)
" Check your CMOS/BIOS settings.\n");
now.tv_sec = 0;
now.tv_nsec = 0;
- } else if (now.tv_sec || now.tv_nsec)
+ } else if (now.tv_sec || now.tv_nsec) {
persistent_clock_exist = true;
+ systime_was_set = true;
+ }

read_boot_clock(&boot);
if (!timespec_valid_strict(&boot)) {
--
1.8.1.5


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