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manager: use max of: compile epoch, epoch file, timesyncd file

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Previously systemd would not use /var/lib/systemd/timesync/clock. This means
that even if /var/ is mounted when systemd is started and the file is
available, we would potentially make one time jump and than another time jump.
From a user's POV, this doesn't seem useful at all.

Also, we would always let /usr/lib/clock-epoch take priority over the built-in
epoch. But there is no guarantee that this file is actually fresh. In
particular, a user may touch /usr/lib/clock-epoch to work around a broken clock
during installation (as recommended in [1]), and then this file will grow stale
over time.

So just load the three timestamps and use the highest one as the epoch.

[1] https://discussion.fedoraproject.org/t/f38-to-f39-40-dnf-system-upgrade-can-fail-on-raspberry-pi/92403
This commit is contained in:
Zbigniew Jędrzejewski-Szmek 2024-06-05 12:50:52 +02:00
parent 18c5979465
commit ed23f7cbcb
1 changed files with 18 additions and 8 deletions
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26
src/core/clock-warp.c
View file

@ -19,18 +19,28 @@ int clock_reset_timewarp(void) {
}
void clock_apply_epoch(void) {
usec_t epoch_usec;
usec_t epoch_usec = 0, timesyncd_usec = 0;
struct stat st;
int r;
r = RET_NERRNO(stat(EPOCH_CLOCK_FILE, &st));
if (r < 0) {
if (r != -ENOENT)
log_warning_errno(r, "Cannot stat " EPOCH_CLOCK_FILE ": %m");
epoch_usec = (usec_t) TIME_EPOCH * USEC_PER_SEC;
} else
r = RET_NERRNO(stat(TIMESYNCD_CLOCK_FILE, &st));
if (r >= 0)
epoch_usec = timespec_load(&st.st_mtim);
else if (r != -ENOENT)
log_warning_errno(r, "Could not stat %s, ignoring: %m", TIMESYNCD_CLOCK_FILE);
r = RET_NERRNO(stat(EPOCH_CLOCK_FILE, &st));
if (r >= 0)
timesyncd_usec = timespec_load(&st.st_mtim);
else if (r != -ENOENT)
log_warning_errno(r, "Could not stat %s, ignoring: %m", EPOCH_CLOCK_FILE);
epoch_usec = MAX3(epoch_usec,
timesyncd_usec,
(usec_t) TIME_EPOCH * USEC_PER_SEC);
if (epoch_usec == 0) /* Weird, but may happen if mtimes were reset to 0 during compilation. */
return log_debug("Clock epoch is 0, skipping clock adjustment.");
usec_t now_usec = now(CLOCK_REALTIME);
bool advance;