From 351619fc99883d22ba1018b5914ae717bfef4221 Mon Sep 17 00:00:00 2001 From: Anna-Maria Behnsen Date: Wed, 9 Oct 2024 10:29:11 +0200 Subject: [PATCH] timekeeping: Rework change_clocksource() to use shadow_timekeeper Updates of the timekeeper can be done by operating on the shadow timekeeper and afterwards copying the result into the real timekeeper. This has the advantage, that the sequence count write protected region is kept as small as possible. Convert change_clocksource() to use this scheme. Signed-off-by: Anna-Maria Behnsen Signed-off-by: Thomas Gleixner Acked-by: John Stultz Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-18-554456a44a15@linutronix.de --- kernel/time/timekeeping.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 7e865f0579359..f77782f557ce9 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1627,9 +1627,7 @@ static void __timekeeping_set_tai_offset(struct timekeeper *tk, s32 tai_offset) */ static int change_clocksource(void *data) { - struct timekeeper *tk = &tk_core.timekeeper; struct clocksource *new = data, *old = NULL; - unsigned long flags; /* * If the clocksource is in a module, get a module reference. @@ -1645,16 +1643,14 @@ static int change_clocksource(void *data) return 0; } - raw_spin_lock_irqsave(&tk_core.lock, flags); - write_seqcount_begin(&tk_core.seq); - - timekeeping_forward_now(tk); - old = tk->tkr_mono.clock; - tk_setup_internals(tk, new); - timekeeping_update(&tk_core, tk, TK_UPDATE_ALL | TK_MIRROR); + scoped_guard (raw_spinlock_irqsave, &tk_core.lock) { + struct timekeeper *tks = &tk_core.shadow_timekeeper; - write_seqcount_end(&tk_core.seq); - raw_spin_unlock_irqrestore(&tk_core.lock, flags); + timekeeping_forward_now(tks); + old = tks->tkr_mono.clock; + tk_setup_internals(tks, new); + timekeeping_update_from_shadow(&tk_core, TK_UPDATE_ALL); + } if (old) { if (old->disable) -- 2.50.1