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authorThomas Gleixner <tglx@linutronix.de>2019-06-13 21:40:45 +0200
committerThomas Gleixner <tglx@linutronix.de>2019-06-14 11:51:44 +0200
commite3ff9c3678b4d80e22d2557b68726174578eaf52 (patch)
tree5cf1422bf9b708b1402ccd93d6a7edb34d368010
parent6cb3dd75b00e987f5aaa515a4977d3f3ffd0b651 (diff)
downloadlinux-sh-e3ff9c3678b4d80e22d2557b68726174578eaf52.tar.gz
timekeeping: Repair ktime_get_coarse*() granularity
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.linutronix.de
-rw-r--r--kernel/time/timekeeping.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 85f5912d8f70..44b726bab4bd 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -808,17 +808,18 @@ ktime_t ktime_get_coarse_with_offset(enum tk_offsets offs)
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);