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authorAnna-Maria Behnsen <anna-maria@linutronix.de>2024-10-09 10:29:10 +0200
committerThomas Gleixner <tglx@linutronix.de>2024-10-25 19:49:15 +0200
commit82214756d35f48056fe36aa4d95a22e44a3b2619 (patch)
tree0bae242dccbfb8a1bb4c4e0a1feb8247a062730b
parentbba9898ef399667b2afe5f79407f1595157c1374 (diff)
downloadlwn-82214756d35f48056fe36aa4d95a22e44a3b2619.tar.gz
lwn-82214756d35f48056fe36aa4d95a22e44a3b2619.zip
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: 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-v2-17-554456a44a15@linutronix.de
-rw-r--r--kernel/time/timekeeping.c41
1 files changed, 16 insertions, 25 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 1b8db1191614..7e865f057935 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -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);
-
- timekeeping_forward_now(tk);
-
- /* Make sure the proposed value is valid */
- tmp = timespec64_add(tk_xtime(tk), *ts);
- if (timespec64_compare(&tk->wall_to_monotonic, ts) > 0 ||
- !timespec64_valid_settod(&tmp)) {
- ret = -EINVAL;
- goto error;
- }
+ scoped_guard (raw_spinlock_irqsave, &tk_core.lock) {
+ struct timekeeper *tks = &tk_core.shadow_timekeeper;
+ struct timespec64 tmp;
- tk_xtime_add(tk, ts);
- tk_set_wall_to_mono(tk, timespec64_sub(tk->wall_to_monotonic, *ts));
+ timekeeping_forward_now(tks);
-error: /* even if we error out, we forwarded the time, so call update */
- timekeeping_update(&tk_core, tk, TK_UPDATE_ALL | TK_MIRROR);
+ /* Make sure the proposed value is valid */
+ tmp = timespec64_add(tk_xtime(tks), *ts);
+ if (timespec64_compare(&tks->wall_to_monotonic, ts) > 0 ||
+ !timespec64_valid_settod(&tmp)) {
+ timekeeping_restore_shadow(&tk_core);
+ return -EINVAL;
+ }
- 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;
}
/*