diff mbox series

[v2,15/25] timekeeping: Provide timekeeping_restore_shadow()

Message ID 20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-15-554456a44a15@linutronix.de (mailing list archive)
State Not Applicable
Headers show
Series timekeeping: 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 Oct. 9, 2024, 8:29 a.m. UTC 
From: Thomas Gleixner <tglx@linutronix.de>

From: Thomas Gleixner <tglx@linutronix.de>

Functions which operate on the real timekeeper, e.g. do_settimeofday(),
have error conditions. If they are hit a full timekeeping update is still
required because the already committed operations modified the timekeeper.

When switching these functions to operate on the shadow timekeeper then the
full update can be avoided in the error case, but the modified shadow
timekeeper has to be restored.

Provide a helper function for that.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
---
 kernel/time/timekeeping.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

Comments

John Stultz Oct. 24, 2024, 9:45 p.m. UTC | #1 
On Wed, Oct 9, 2024 at 1:29 AM Anna-Maria Behnsen
<anna-maria@linutronix.de> wrote:
>
> From: Thomas Gleixner <tglx@linutronix.de>
>
> From: Thomas Gleixner <tglx@linutronix.de>
>
> Functions which operate on the real timekeeper, e.g. do_settimeofday(),
> have error conditions. If they are hit a full timekeeping update is still
> required because the already committed operations modified the timekeeper.
>
> When switching these functions to operate on the shadow timekeeper then the
> full update can be avoided in the error case, but the modified shadow
> timekeeper has to be restored.
>
> Provide a helper function for that.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>

Acked-by: John Stultz <jstultz@google.com>
diff mbox series

Patch

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 5a747afe64b4..41d88f645868 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -755,6 +755,15 @@  static inline void tk_update_ktime_data(struct timekeeper *tk)
 	tk->tkr_raw.base = ns_to_ktime(tk->raw_sec * NSEC_PER_SEC);
 }
 
+/*
+ * Restore the shadow timekeeper from the real timekeeper.
+ */
+static void timekeeping_restore_shadow(struct tk_data *tkd)
+{
+	lockdep_assert_held(&tkd->lock);
+	memcpy(&tkd->shadow_timekeeper, &tkd->timekeeper, sizeof(tkd->timekeeper));
+}
+
 static void timekeeping_update(struct tk_data *tkd, struct timekeeper *tk, unsigned int action)
 {
 	lockdep_assert_held(&tkd->lock);
@@ -782,7 +791,7 @@  static void timekeeping_update(struct tk_data *tkd, struct timekeeper *tk, unsig
 	 * timekeeper structure on the next update with stale data
 	 */
 	if (action & TK_MIRROR)
-		memcpy(&tkd->shadow_timekeeper, tk, sizeof(*tk));
+		timekeeping_restore_shadow(tkd);
 }
 
 static void timekeeping_update_staged(struct tk_data *tkd, unsigned int action)