linux-kernel - [PATCH v2 02/25] timekeeping: Don't stop time readers across hard

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Message-Id: <20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-2-554456a44a15@linutronix.de>
Date: Wed, 09 Oct 2024 10:28:55 +0200
From: Anna-Maria Behnsen <anna-maria@...utronix.de>
To: John Stultz <jstultz@...gle.com>, 
 Frederic Weisbecker <frederic@...nel.org>, 
 Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
 Miroslav Lichvar <mlichvar@...hat.com>, 
 Richard Cochran <richardcochran@...il.com>, 
 Christopher S Hall <christopher.s.hall@...el.com>, 
 Anna-Maria Behnsen <anna-maria@...utronix.de>
Subject: [PATCH v2 02/25] timekeeping: Don't stop time readers across
 hard_pps() update

From: Thomas Gleixner <tglx@...utronix.de>

From: Thomas Gleixner <tglx@...utronix.de>

hard_pps() update does not modify anything which might be required by time
readers so forcing readers out of the way during the update is a pointless
exercise.

The interaction with adjtimex() and timekeeper updates which call into the
NTP code is properly serialized by timekeeper_lock.

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

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 6acff4cb7b1c..4e3afe22d28c 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -2627,11 +2627,7 @@ void hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
 	unsigned long flags;
 
 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
-	write_seqcount_begin(&tk_core.seq);
-
 	__hardpps(phase_ts, raw_ts);
-
-	write_seqcount_end(&tk_core.seq);
 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
 }
 EXPORT_SYMBOL(hardpps);

-- 
2.39.5