linux-kernel - [PATCH] time: avoid timespec in udelay

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Message-Id: <20160617160312.1096279-1-arnd@arndb.de>
Date:	Fri, 17 Jun 2016 18:03:02 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	y2038@...ts.linaro.org, Arnd Bergmann <arnd@...db.de>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] time: avoid timespec in udelay_test

udelay_test_single() uses ktime_get_ts() to get two timespec values
and calculate the difference between them, while udelay_test_show()
uses the same to printk() the current monotonic time.

Both of these are y2038 safe on all machines, but we want to
get rid of struct timespec anyway, so this converts the code to
use ktime_get_ns() and ktime_get_ts64() respectively.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 kernel/time/test_udelay.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/time/test_udelay.c b/kernel/time/test_udelay.c
index e622ba365a13..b0928ab3270f 100644
--- a/kernel/time/test_udelay.c
+++ b/kernel/time/test_udelay.c
@@ -43,13 +43,13 @@ static int udelay_test_single(struct seq_file *s, int usecs, uint32_t iters)
 	int allowed_error_ns = usecs * 5;
 
 	for (i = 0; i < iters; ++i) {
-		struct timespec ts1, ts2;
+		s64 kt1, kt2;
 		int time_passed;
 
-		ktime_get_ts(&ts1);
+		kt1 = ktime_get_ns();
 		udelay(usecs);
-		ktime_get_ts(&ts2);
-		time_passed = timespec_to_ns(&ts2) - timespec_to_ns(&ts1);
+		kt2 = ktime_get_ns();
+		time_passed = kt2 - kt1;
 
 		if (i == 0 || time_passed < min)
 			min = time_passed;
@@ -87,11 +87,11 @@ static int udelay_test_show(struct seq_file *s, void *v)
 	if (usecs > 0 && iters > 0) {
 		return udelay_test_single(s, usecs, iters);
 	} else if (usecs == 0) {
-		struct timespec ts;
+		struct timespec64 ts;
 
-		ktime_get_ts(&ts);
-		seq_printf(s, "udelay() test (lpj=%ld kt=%ld.%09ld)\n",
-				loops_per_jiffy, ts.tv_sec, ts.tv_nsec);
+		ktime_get_ts64(&ts);
+		seq_printf(s, "udelay() test (lpj=%ld kt=%lld.%09ld)\n",
+				loops_per_jiffy, (s64)ts.tv_sec, ts.tv_nsec);
 		seq_puts(s, "usage:\n");
 		seq_puts(s, "echo USECS [ITERS] > " DEBUGFS_FILENAME "\n");
 		seq_puts(s, "cat " DEBUGFS_FILENAME "\n");
-- 
2.9.0