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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 <anna-maria@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: John Stultz <jstultz@google.com> Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-16-554456a44a15@linutronix.de
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@ -1510,45 +1510,35 @@ EXPORT_SYMBOL_GPL(timekeeping_clocksource_has_base);
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*/
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int do_settimeofday64(const struct timespec64 *ts)
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{
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struct timekeeper *tk = &tk_core.timekeeper;
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struct timespec64 ts_delta, xt;
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unsigned long flags;
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int ret = 0;
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if (!timespec64_valid_settod(ts))
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return -EINVAL;
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raw_spin_lock_irqsave(&tk_core.lock, flags);
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write_seqcount_begin(&tk_core.seq);
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scoped_guard (raw_spinlock_irqsave, &tk_core.lock) {
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struct timekeeper *tks = &tk_core.shadow_timekeeper;
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timekeeping_forward_now(tk);
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timekeeping_forward_now(tks);
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xt = tk_xtime(tk);
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ts_delta = timespec64_sub(*ts, xt);
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xt = tk_xtime(tks);
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ts_delta = timespec64_sub(*ts, xt);
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if (timespec64_compare(&tk->wall_to_monotonic, &ts_delta) > 0) {
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ret = -EINVAL;
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goto out;
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if (timespec64_compare(&tks->wall_to_monotonic, &ts_delta) > 0) {
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timekeeping_restore_shadow(&tk_core);
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return -EINVAL;
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}
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tk_set_wall_to_mono(tks, timespec64_sub(tks->wall_to_monotonic, ts_delta));
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tk_set_xtime(tks, ts);
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timekeeping_update_from_shadow(&tk_core, TK_UPDATE_ALL);
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}
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tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, ts_delta));
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tk_set_xtime(tk, ts);
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out:
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timekeeping_update(&tk_core, tk, TK_UPDATE_ALL | TK_MIRROR);
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write_seqcount_end(&tk_core.seq);
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raw_spin_unlock_irqrestore(&tk_core.lock, flags);
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/* Signal hrtimers about time change */
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clock_was_set(CLOCK_SET_WALL);
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if (!ret) {
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audit_tk_injoffset(ts_delta);
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add_device_randomness(ts, sizeof(*ts));
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}
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return ret;
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audit_tk_injoffset(ts_delta);
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add_device_randomness(ts, sizeof(*ts));
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return 0;
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}
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EXPORT_SYMBOL(do_settimeofday64);
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