kdb: use ktime_get_mono_fast_ns() instead of ktime_get_ts()

The kdb code will print the monotonic time by ktime_get_ts(), but
the ktime_get_ts() will be protected by a sequence lock, that will
introduce one deadlock risk if the lock was already held in the
context from which we entered the debugger.

Thus we can use the ktime_get_mono_fast_ns() to get the monotonic
time, which is NMI safe access to clock monotonic. Moreover we can
remove the 'struct timespec', which is not y2038 safe.
Signed-off-by: NBaolin Wang <baolin.wang@linaro.org>
Reviewed-by: NDaniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>

kernel/debug/kdb/kdb_main.c

@@ -2512,10 +2512,10 @@ static int kdb_kill(int argc, const char **argv)
  */
 static void kdb_sysinfo(struct sysinfo *val)
 {
-	struct timespec uptime;
-	ktime_get_ts(&uptime);
+	u64 uptime = ktime_get_mono_fast_ns();
+
 	memset(val, 0, sizeof(*val));
-	val->uptime = uptime.tv_sec;
+	val->uptime = div_u64(uptime, NSEC_PER_SEC);
 	val->loads[0] = avenrun[0];
 	val->loads[1] = avenrun[1];
 	val->loads[2] = avenrun[2];