From bba9898ef399667b2afe5f79407f1595157c1374 Mon Sep 17 00:00:00 2001 From: Anna-Maria Behnsen Date: Wed, 9 Oct 2024 10:29:09 +0200 Subject: [PATCH] timekeeping: Rework do_settimeofday64() 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 do_settimeofday64() to use this scheme. That allows to use a scoped_guard() for locking the timekeeper lock as the usage of the shadow timekeeper allows a rollback in the error case instead of the full timekeeper update of the original code. 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-v2-16-554456a44a15@linutronix.de --- kernel/time/timekeeping.c | 42 +++++++++++++++------------------------ 1 file changed, 16 insertions(+), 26 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index ed0e328fedd02..1b8db11916148 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1510,45 +1510,35 @@ EXPORT_SYMBOL_GPL(timekeeping_clocksource_has_base); */ int do_settimeofday64(const struct timespec64 *ts) { - struct timekeeper *tk = &tk_core.timekeeper; struct timespec64 ts_delta, xt; - unsigned long flags; - int ret = 0; if (!timespec64_valid_settod(ts)) return -EINVAL; - raw_spin_lock_irqsave(&tk_core.lock, flags); - write_seqcount_begin(&tk_core.seq); - - timekeeping_forward_now(tk); - - xt = tk_xtime(tk); - ts_delta = timespec64_sub(*ts, xt); + scoped_guard (raw_spinlock_irqsave, &tk_core.lock) { + struct timekeeper *tks = &tk_core.shadow_timekeeper; - if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) { - ret = -EINVAL; - goto out; - } + timekeeping_forward_now(tks); - tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta)); + xt = tk_xtime(tks); + ts_delta = timespec64_sub(*ts, xt); - tk_set_xtime(tk, ts); -out: - timekeeping_update(&tk_core, tk, TK_UPDATE_ALL | TK_MIRROR); + if (timespec64_compare(&tks->wall_to_monotonic, &ts_delta) > 0) { + timekeeping_restore_shadow(&tk_core); + return -EINVAL; + } - write_seqcount_end(&tk_core.seq); - raw_spin_unlock_irqrestore(&tk_core.lock, flags); + tk_set_wall_to_mono(tks, timespec64_sub(tks->wall_to_monotonic, ts_delta)); + tk_set_xtime(tks, ts); + timekeeping_update_from_shadow(&tk_core, TK_UPDATE_ALL); + } /* Signal hrtimers about time change */ clock_was_set(CLOCK_SET_WALL); - if (!ret) { - audit_tk_injoffset(ts_delta); - add_device_randomness(ts, sizeof(*ts)); - } - - return ret; + audit_tk_injoffset(ts_delta); + add_device_randomness(ts, sizeof(*ts)); + return 0; } EXPORT_SYMBOL(do_settimeofday64); -- 2.50.1