diff mbox series

[v2,07/25] timekeeping: Move shadow_timekeeper into tk_core

Message ID 20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-7-554456a44a15@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>

tk_core requires shadow_timekeeper to allow timekeeping_advance() updating
without holding the timekeeper sequence count write locked. This allows the
readers to make progress up to the actual update where the shadow
timekeeper is copied over to the real timekeeper.

As long as there is only a single timekeeper, having them separate is
fine. But when the timekeeper infrastructure will be reused for per ptp
clock timekeepers, shadow_timekeeper needs to be part of tk_core.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
---
 kernel/time/timekeeping.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

Comments

John Stultz Oct. 24, 2024, 9:11 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>
>
> tk_core requires shadow_timekeeper to allow timekeeping_advance() updating
> without holding the timekeeper sequence count write locked. This allows the
> readers to make progress up to the actual update where the shadow
> timekeeper is copied over to the real timekeeper.
>
> As long as there is only a single timekeeper, having them separate is
> fine. But when the timekeeper infrastructure will be reused for per ptp
> clock timekeepers, shadow_timekeeper needs to be part of tk_core.
>
> No functional change.
>
> 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 e747e46a1a2d..267b28cf2ab0 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -50,11 +50,11 @@  DEFINE_RAW_SPINLOCK(timekeeper_lock);
 static struct {
 	seqcount_raw_spinlock_t	seq;
 	struct timekeeper	timekeeper;
+	struct timekeeper	shadow_timekeeper;
 } tk_core ____cacheline_aligned = {
 	.seq = SEQCNT_RAW_SPINLOCK_ZERO(tk_core.seq, &timekeeper_lock),
 };
 
-static struct timekeeper shadow_timekeeper;
 
 /* flag for if timekeeping is suspended */
 int __read_mostly timekeeping_suspended;
@@ -776,8 +776,7 @@  static void timekeeping_update(struct timekeeper *tk, unsigned int action)
 	 * timekeeper structure on the next update with stale data
 	 */
 	if (action & TK_MIRROR)
-		memcpy(&shadow_timekeeper, &tk_core.timekeeper,
-		       sizeof(tk_core.timekeeper));
+		memcpy(&tk_core.shadow_timekeeper, &tk_core.timekeeper, sizeof(tk_core.timekeeper));
 }
 
 /**
@@ -2274,8 +2273,8 @@  static u64 logarithmic_accumulation(struct timekeeper *tk, u64 offset,
  */
 static bool timekeeping_advance(enum timekeeping_adv_mode mode)
 {
+	struct timekeeper *tk = &tk_core.shadow_timekeeper;
 	struct timekeeper *real_tk = &tk_core.timekeeper;
-	struct timekeeper *tk = &shadow_timekeeper;
 	unsigned int clock_set = 0;
 	int shift = 0, maxshift;
 	u64 offset;