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-rw-r--r--kernel/time.c32
1 files changed, 24 insertions, 8 deletions
diff --git a/kernel/time.c b/kernel/time.c
index f04791f6940..ffe19149d77 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -57,14 +57,17 @@ EXPORT_SYMBOL(sys_tz);
*/
asmlinkage long sys_time(time_t __user * tloc)
{
- time_t i;
- struct timeval tv;
+ /*
+ * We read xtime.tv_sec atomically - it's updated
+ * atomically by update_wall_time(), so no need to
+ * even read-lock the xtime seqlock:
+ */
+ time_t i = xtime.tv_sec;
- do_gettimeofday(&tv);
- i = tv.tv_sec;
+ smp_rmb(); /* sys_time() results are coherent */
if (tloc) {
- if (put_user(i,tloc))
+ if (put_user(i, tloc))
i = -EFAULT;
}
return i;
@@ -373,12 +376,25 @@ void do_gettimeofday (struct timeval *tv)
tv->tv_sec = sec;
tv->tv_usec = usec;
-}
+ /*
+ * Make sure xtime.tv_sec [returned by sys_time()] always
+ * follows the gettimeofday() result precisely. This
+ * condition is extremely unlikely, it can hit at most
+ * once per second:
+ */
+ if (unlikely(xtime.tv_sec != tv->tv_sec)) {
+ unsigned long flags;
+
+ write_seqlock_irqsave(&xtime_lock, flags);
+ update_wall_time();
+ write_sequnlock_irqrestore(&xtime_lock, flags);
+ }
+}
EXPORT_SYMBOL(do_gettimeofday);
+#else /* CONFIG_TIME_INTERPOLATION */
-#else
#ifndef CONFIG_GENERIC_TIME
/*
* Simulate gettimeofday using do_gettimeofday which only allows a timeval
@@ -394,7 +410,7 @@ void getnstimeofday(struct timespec *tv)
}
EXPORT_SYMBOL_GPL(getnstimeofday);
#endif
-#endif
+#endif /* CONFIG_TIME_INTERPOLATION */
/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
* Assumes input in normal date format, i.e. 1980-12-31 23:59:59