diff mbox series

[06/21] ntp: Read reference time only once

Message ID 20240911-devel-anna-maria-b4-timers-ptp-ntp-v1-6-2d52f4e13476@linutronix.de (mailing list archive)
State Not Applicable
Headers show
Series ntp: Rework to prepare support of indenpendent PTP clocks | expand

Checks

Context Check Description
netdev/tree_selection success Not a local patch

Commit Message

Anna-Maria Behnsen Sept. 11, 2024, 1:17 p.m. UTC 
From: Thomas Gleixner <tglx@linutronix.de>

The reference time is required twice in ntp_update_offset(). It will not
change in the meantime as the calling code holds the timekeeper lock. Read
it only once and store it into a local variable.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
---
 kernel/time/ntp.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Comments

John Stultz Sept. 11, 2024, 8 p.m. UTC | #1 
On Wed, Sep 11, 2024 at 6:18 AM Anna-Maria Behnsen
<anna-maria@linutronix.de> wrote:
>
> From: Thomas Gleixner <tglx@linutronix.de>
>
> The reference time is required twice in ntp_update_offset(). It will not
> change in the meantime as the calling code holds the timekeeper lock. Read
> it only once and store it into a local variable.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
> ---

Nice!
Acked-by: John Stultz <jstultz@google.com>

thanks
-john
diff mbox series

Patch

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index ef758aafdfd5..477cb08062bc 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -283,9 +283,8 @@  static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
 
 static void ntp_update_offset(long offset)
 {
-	s64 freq_adj;
-	s64 offset64;
-	long secs;
+	s64 freq_adj, offset64;
+	long secs, real_secs;
 
 	if (!(time_status & STA_PLL))
 		return;
@@ -303,11 +302,12 @@  static void ntp_update_offset(long offset)
 	 * Select how the frequency is to be controlled
 	 * and in which mode (PLL or FLL).
 	 */
-	secs = (long)(__ktime_get_real_seconds() - time_reftime);
+	real_secs = __ktime_get_real_seconds();
+	secs = (long)(real_secs - time_reftime);
 	if (unlikely(time_status & STA_FREQHOLD))
 		secs = 0;
 
-	time_reftime = __ktime_get_real_seconds();
+	time_reftime = real_secs;
 
 	offset64    = offset;
 	freq_adj    = ntp_update_offset_fll(offset64, secs);