From: Peter Hilber peter.hilber@opensynergy.com
[ Upstream commit 14274d0bd31b4debf28284604589f596ad2e99f2 ]
So far, get_device_system_crosststamp() unconditionally passes system_counterval.cycles to timekeeping_cycles_to_ns(). But when interpolating system time (do_interp == true), system_counterval.cycles is before tkr_mono.cycle_last, contrary to the timekeeping_cycles_to_ns() expectations.
On x86, CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE will mitigate on interpolating, setting delta to 0. With delta == 0, xtstamp->sys_monoraw and xtstamp->sys_realtime are then set to the last update time, as implicitly expected by adjust_historical_crosststamp(). On other architectures, the resulting nonsense xtstamp->sys_monoraw and xtstamp->sys_realtime corrupt the xtstamp (ts) adjustment in adjust_historical_crosststamp().
Fix this by deriving xtstamp->sys_monoraw and xtstamp->sys_realtime from the last update time when interpolating, by using the local variable "cycles". The local variable already has the right value when interpolating, unlike system_counterval.cycles.
Fixes: 2c756feb18d9 ("time: Add history to cross timestamp interface supporting slower devices") Signed-off-by: Peter Hilber peter.hilber@opensynergy.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: John Stultz jstultz@google.com Link: https://lore.kernel.org/r/20231218073849.35294-4-peter.hilber@opensynergy.co... Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/time/timekeeping.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index d21280b3b2ea7..dfa6649c490de 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1244,10 +1244,8 @@ int get_device_system_crosststamp(int (*get_time_fn) tk_core.timekeeper.offs_real); base_raw = tk->tkr_raw.base;
- nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, - system_counterval.cycles); - nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw, - system_counterval.cycles); + nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, cycles); + nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw, cycles); } while (read_seqcount_retry(&tk_core.seq, seq));
xtstamp->sys_realtime = ktime_add_ns(base_real, nsec_real);