Commit 82214756 authored by Anna-Maria Behnsen's avatar Anna-Maria Behnsen Committed by Thomas Gleixner
Browse files

timekeeping: Rework timekeeping_inject_offset() 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 timekeeping_inject_offset() 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: default avatarAnna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarJohn Stultz <jstultz@google.com>
Link: https://lore.kernel.org/all/20241009-devel-anna-maria-b4-timers-ptp-timekeeping-v2-17-554456a44a15@linutronix.de
parent bba9898e

kernel/time/timekeeping.c

+16 −25
Original line number Diff line number Diff line
@@ -1550,40 +1550,31 @@ EXPORT_SYMBOL(do_settimeofday64); 
 */

static int timekeeping_inject_offset(const struct timespec64 *ts)

{

	struct timekeeper *tk = &tk_core.timekeeper;

	unsigned long flags;

	struct timespec64 tmp;

	int ret = 0;



	if (ts->tv_nsec < 0 || ts->tv_nsec >= NSEC_PER_SEC)

		return -EINVAL;



	raw_spin_lock_irqsave(&tk_core.lock, flags);

	write_seqcount_begin(&tk_core.seq);

	scoped_guard (raw_spinlock_irqsave, &tk_core.lock) {

		struct timekeeper *tks = &tk_core.shadow_timekeeper;

		struct timespec64 tmp;



	timekeeping_forward_now(tk);

		timekeeping_forward_now(tks);



		/* Make sure the proposed value is valid */

	tmp = timespec64_add(tk_xtime(tk), *ts);

	if (timespec64_compare(&tk->wall_to_monotonic, ts) > 0 ||

		tmp = timespec64_add(tk_xtime(tks), *ts);

		if (timespec64_compare(&tks->wall_to_monotonic, ts) > 0 ||

		    !timespec64_valid_settod(&tmp)) {

		ret = -EINVAL;

		goto error;

			timekeeping_restore_shadow(&tk_core);

			return -EINVAL;

		}



	tk_xtime_add(tk, ts);

	tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *ts));



error: /* even if we error out, we forwarded the time, so call update */

	timekeeping_update(&tk_core, tk, TK_UPDATE_ALL | TK_MIRROR);



	write_seqcount_end(&tk_core.seq);

	raw_spin_unlock_irqrestore(&tk_core.lock, flags);

		tk_xtime_add(tks, ts);

		tk_set_wall_to_mono(tks, timespec64_sub(tks->wall_to_monotonic, *ts));

		timekeeping_update_from_shadow(&tk_core, TK_UPDATE_ALL);

	}



	/* Signal hrtimers about time change */

	clock_was_set(CLOCK_SET_WALL);



	return ret;

	return 0;

}



/*