diff mbox

ntp:Fix second_overflow's input parameter type

Message ID 1449980802-3026-1-git-send-email-chao.deng@linaro.org
State New
Headers show

Commit Message

Deng Chao Dec. 13, 2015, 4:26 a.m. UTC 
The function "second_overflow" uses "unsign long"
as its input parameter type which will overflow after
year 2106 on 32bit systems.
Replace it with time64_t type.
Because 64-bit division is expensive, since "next_ntp_leap_sec"
has been calculated already, we can just re-use it in the
TIME_INS/DEL cases instead of re-doing divsion which may occur
once a second.
Signed-off-by: DengChao <chao.deng@linaro.org>

---
 kernel/time/ntp.c          | 16 +++++++++-------
 kernel/time/ntp_internal.h |  2 +-
 2 files changed, 10 insertions(+), 8 deletions(-)

-- 
1.9.1

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Comments

John Stultz Dec. 16, 2015, 6:12 a.m. UTC | #1 
On Sat, Dec 12, 2015 at 8:26 PM, DengChao <chao.deng@linaro.org> wrote:
> The function "second_overflow" uses "unsign long"

> as its input parameter type which will overflow after

> year 2106 on 32bit systems.

> Replace it with time64_t type.

> Because 64-bit division is expensive, since "next_ntp_leap_sec"

> has been calculated already, we can just re-use it in the

> TIME_INS/DEL cases instead of re-doing divsion which may occur

> once a second.

> Signed-off-by: DengChao <chao.deng@linaro.org>


Queued for testing. I reworded the commit message a bit too.

thanks
-john
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diff mbox

Patch

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 149cc80..37479305 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -16,6 +16,7 @@ 
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/rtc.h>
+#include <linux/math64.h>
 
 #include "ntp_internal.h"
 
@@ -390,10 +391,11 @@  ktime_t ntp_get_next_leap(void)
  *
  * Also handles leap second processing, and returns leap offset
  */
-int second_overflow(unsigned long secs)
+int second_overflow(time64_t secs)
 {
 	s64 delta;
 	int leap = 0;
+	s32 rem;
 
 	/*
 	 * Leap second processing. If in leap-insert state at the end of the
@@ -404,19 +406,19 @@  int second_overflow(unsigned long secs)
 	case TIME_OK:
 		if (time_status & STA_INS) {
 			time_state = TIME_INS;
-			ntp_next_leap_sec = secs + SECS_PER_DAY -
-						(secs % SECS_PER_DAY);
+			div_s64_rem(secs, SECS_PER_DAY, &rem);
+			ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
 		} else if (time_status & STA_DEL) {
 			time_state = TIME_DEL;
-			ntp_next_leap_sec = secs + SECS_PER_DAY -
-						 ((secs+1) % SECS_PER_DAY);
+			div_s64_rem(secs + 1, SECS_PER_DAY, &rem);
+			ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
 		}
 		break;
 	case TIME_INS:
 		if (!(time_status & STA_INS)) {
 			ntp_next_leap_sec = TIME64_MAX;
 			time_state = TIME_OK;
-		} else if (secs % SECS_PER_DAY == 0) {
+		} else if (secs == ntp_next_leap_sec) {
 			leap = -1;
 			time_state = TIME_OOP;
 			printk(KERN_NOTICE
@@ -427,7 +429,7 @@  int second_overflow(unsigned long secs)
 		if (!(time_status & STA_DEL)) {
 			ntp_next_leap_sec = TIME64_MAX;
 			time_state = TIME_OK;
-		} else if ((secs + 1) % SECS_PER_DAY == 0) {
+		} else if (secs == ntp_next_leap_sec) {
 			leap = 1;
 			ntp_next_leap_sec = TIME64_MAX;
 			time_state = TIME_WAIT;
diff --git a/kernel/time/ntp_internal.h b/kernel/time/ntp_internal.h
index af92447..d8a7c11 100644
--- a/kernel/time/ntp_internal.h
+++ b/kernel/time/ntp_internal.h
@@ -6,7 +6,7 @@  extern void ntp_clear(void);
 /* Returns how long ticks are at present, in ns / 2^NTP_SCALE_SHIFT. */
 extern u64 ntp_tick_length(void);
 extern ktime_t ntp_get_next_leap(void);
-extern int second_overflow(unsigned long secs);
+extern int second_overflow(time64_t secs);
 extern int ntp_validate_timex(struct timex *);
 extern int __do_adjtimex(struct timex *, struct timespec64 *, s32 *);
 extern void __hardpps(const struct timespec64 *, const struct timespec64 *);