summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorJohn Stultz <john.stultz@linaro.org>2011-02-01 16:52:17 +0300
committerThomas Gleixner <tglx@linutronix.de>2011-02-02 17:28:18 +0300
commitc528f7c6c208f1fae6b4025957173dec045e5f21 (patch)
tree86986bf39f82622ea81179dad3382fc4580875a8
parent0061748dd2400d0bcd4d49d258db5d7b5d106ca0 (diff)
downloadlinux-c528f7c6c208f1fae6b4025957173dec045e5f21.tar.xz
time: Introduce timekeeping_inject_offset
This adds a kernel-internal timekeeping interface to add or subtract a fixed amount from CLOCK_REALTIME. This makes it so kernel users or interfaces trying to do so do not have to read the time, then add an offset and then call settimeofday(), which adds some extra error in comparision to just simply adding the offset in the kernel timekeeping core. Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Richard Cochran <richard.cochran@omicron.at> LKML-Reference: <20110201134419.584311693@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
-rw-r--r--include/linux/time.h1
-rw-r--r--kernel/time/timekeeping.c36
2 files changed, 37 insertions, 0 deletions
diff --git a/include/linux/time.h b/include/linux/time.h
index 7c44e7778033..379b9037b5b4 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -166,6 +166,7 @@ extern struct timespec timespec_trunc(struct timespec t, unsigned gran);
extern int timekeeping_valid_for_hres(void);
extern u64 timekeeping_max_deferment(void);
extern void timekeeping_leap_insert(int leapsecond);
+extern int timekeeping_inject_offset(struct timespec *ts);
struct tms;
extern void do_sys_times(struct tms *);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 4f9f65b91323..6262c1d18397 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -387,6 +387,42 @@ int do_settimeofday(const struct timespec *tv)
EXPORT_SYMBOL(do_settimeofday);
+
+/**
+ * timekeeping_inject_offset - Adds or subtracts from the current time.
+ * @tv: pointer to the timespec variable containing the offset
+ *
+ * Adds or subtracts an offset value from the current time.
+ */
+int timekeeping_inject_offset(struct timespec *ts)
+{
+ unsigned long flags;
+
+ if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
+ return -EINVAL;
+
+ write_seqlock_irqsave(&xtime_lock, flags);
+
+ timekeeping_forward_now();
+
+ xtime = timespec_add(xtime, *ts);
+ wall_to_monotonic = timespec_sub(wall_to_monotonic, *ts);
+
+ timekeeper.ntp_error = 0;
+ ntp_clear();
+
+ update_vsyscall(&xtime, &wall_to_monotonic, timekeeper.clock,
+ timekeeper.mult);
+
+ write_sequnlock_irqrestore(&xtime_lock, flags);
+
+ /* signal hrtimers about time change */
+ clock_was_set();
+
+ return 0;
+}
+EXPORT_SYMBOL(timekeeping_inject_offset);
+
/**
* change_clocksource - Swaps clocksources if a new one is available
*