From: Thomas Gleixner tglx@linutronix.de
commit e3ff9c3678b4d80e22d2557b68726174578eaf52 upstream.
Jason reported that the coarse ktime based time getters advance only once per second and not once per tick as advertised.
The code reads only the monotonic base time, which advances once per second. The nanoseconds are accumulated on every tick in xtime_nsec up to a second and the regular time getters take this nanoseconds offset into account, but the ktime_get_coarse*() implementation fails to do so.
Add the accumulated xtime_nsec value to the monotonic base time to get the proper per tick advancing coarse tinme.
Fixes: b9ff604cff11 ("timekeeping: Add ktime_get_coarse_with_offset") Reported-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Tested-by: Jason A. Donenfeld Jason@zx2c4.com Cc: Arnd Bergmann arnd@arndb.de Cc: Peter Zijlstra peterz@infradead.org Cc: Clemens Ladisch clemens@ladisch.de Cc: Sultan Alsawaf sultan@kerneltoast.com Cc: Waiman Long longman@redhat.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1906132136280.1791@nanos.tec.linut... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/time/timekeeping.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -812,17 +812,18 @@ ktime_t ktime_get_coarse_with_offset(enu struct timekeeper *tk = &tk_core.timekeeper; unsigned int seq; ktime_t base, *offset = offsets[offs]; + u64 nsecs;
WARN_ON(timekeeping_suspended);
do { seq = read_seqcount_begin(&tk_core.seq); base = ktime_add(tk->tkr_mono.base, *offset); + nsecs = tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift;
} while (read_seqcount_retry(&tk_core.seq, seq));
- return base; - + return base + nsecs; } EXPORT_SYMBOL_GPL(ktime_get_coarse_with_offset);