Commit-ID: 0bcdc0987cce9880436b70836c6a92bb8e744fd1
Gitweb: http://git.kernel.org/tip/0bcdc0987cce9880436b70836c6a92bb8e744fd1
Author: John Stultz <john.stu...@linaro.org>
AuthorDate: Fri, 25 Aug 2017 15:57:04 -0700
Committer: Thomas Gleixner <t...@linutronix.de>
CommitDate: Sat, 26 Aug 2017 16:06:12 +0200
time: Fix ktime_get_raw() incorrect base accumulation
In comqit fc6eead7c1e2 ("time: Clean up CLOCK_MONOTONIC_RAW time
handling"), the following code got mistakenly added to the update of the
raw timekeeper:
/* Update the monotonic raw base */
seconds = tk->raw_sec;
nsec = (u32)(tk->tkr_raw.xtime_nsec >> tk->tkr_raw.shift);
tk->tkr_raw.base = ns_to_ktime(seconds * NSEC_PER_SEC + nsec);
Which adds the raw_sec value and the shifted down raw xtime_nsec to the
base value.
But the read function adds the shifted down tk->tkr_raw.xtime_nsec value
another time, The result of this is that ktime_get_raw() users (which are
all internal users) see the raw time move faster then it should (the rate
at which can vary with the current size of tkr_raw.xtime_nsec), which has
resulted in at least problems with graphics rendering performance.
The change tried to match the monotonic base update logic:
seconds = (u64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec);
nsec = (u32) tk->wall_to_monotonic.tv_nsec;
tk->tkr_mono.base = ns_to_ktime(seconds * NSEC_PER_SEC + nsec);
Which adds the wall_to_monotonic.tv_nsec value, but not the
tk->tkr_mono.xtime_nsec value to the base.
To fix this, simplify the tkr_raw.base accumulation to only accumulate the
raw_sec portion, and do not include the tkr_raw.xtime_nsec portion, which
will be added at read time.
Fixes: fc6eead7c1e2 ("time: Clean up CLOCK_MONOTONIC_RAW time handling")
Reported-and-tested-by: Chris Wilson <ch...@chris-wilson.co.uk>
Signed-off-by: John Stultz <john.stu...@linaro.org>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Cc: Prarit Bhargava <pra...@redhat.com>
Cc: Kevin Brodsky <kevin.brod...@arm.com>
Cc: Richard Cochran <richardcoch...@gmail.com>
Cc: Stephen Boyd <stephen.b...@linaro.org>
Cc: Will Deacon <will.dea...@arm.com>
Cc: Miroslav Lichvar <mlich...@redhat.com>
Cc: Daniel Mentz <danielme...@google.com>
Link:
http://lkml.kernel.org/r/1503701824-1645-1-git-send-email-john.stu...@linaro.org
---
kernel/time/timekeeping.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index cedafa0..7e7e61c 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -637,9 +637,7 @@ static inline void tk_update_ktime_data(struct timekeeper
*tk)
tk->ktime_sec = seconds;
/* Update the monotonic raw base */
- seconds = tk->raw_sec;
- nsec = (u32)(tk->tkr_raw.xtime_nsec >> tk->tkr_raw.shift);
- tk->tkr_raw.base = ns_to_ktime(seconds * NSEC_PER_SEC + nsec);
+ tk->tkr_raw.base = ns_to_ktime(tk->raw_sec * NSEC_PER_SEC);
}
/* must hold timekeeper_lock */
