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author | Peter Hilber <peter.hilber@opensynergy.com> | 2023-12-18 08:38:41 +0100 |
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committer | Sasha Levin <sashal@kernel.org> | 2024-03-26 18:22:34 -0400 |
commit | 20880812b2f8fad4cf269f83bd5266eed31f0208 (patch) | |
tree | 7692a0cff1ef92af2dd9bd5fbdc9edc48e879a11 | |
parent | 86c7cc07eef558e9986a17ac5b6d5f44c8b493bd (diff) | |
download | linux-stable-20880812b2f8fad4cf269f83bd5266eed31f0208.tar.gz linux-stable-20880812b2f8fad4cf269f83bd5266eed31f0208.tar.bz2 linux-stable-20880812b2f8fad4cf269f83bd5266eed31f0208.zip |
timekeeping: Fix cross-timestamp interpolation for non-x86
[ 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.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
-rw-r--r-- | kernel/time/timekeeping.c | 6 |
1 files changed, 2 insertions, 4 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index ab36b20cdbec..e43706e2c038 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1172,10 +1172,8 @@ 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); |