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authorJohn Stultz <john.stultz@linaro.org>2017-08-25 15:57:04 -0700
committerThomas Gleixner <tglx@linutronix.de>2017-08-26 16:06:12 +0200
commit0bcdc0987cce9880436b70836c6a92bb8e744fd1 (patch)
tree029e2d8def8b9741e872bb458ae9407ee7a49ee5 /kernel
parent2fe59f507a65dbd734b990a11ebc7488f6f87a24 (diff)
downloadlinux-0bcdc0987cce9880436b70836c6a92bb8e744fd1.tar.bz2
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 <chris@chris-wilson.co.uk> Signed-off-by: John Stultz <john.stultz@linaro.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Prarit Bhargava <prarit@redhat.com> Cc: Kevin Brodsky <kevin.brodsky@arm.com> Cc: Richard Cochran <richardcochran@gmail.com> Cc: Stephen Boyd <stephen.boyd@linaro.org> Cc: Will Deacon <will.deacon@arm.com> Cc: Miroslav Lichvar <mlichvar@redhat.com> Cc: Daniel Mentz <danielmentz@google.com> Link: http://lkml.kernel.org/r/1503701824-1645-1-git-send-email-john.stultz@linaro.org
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/timekeeping.c4
1 files changed, 1 insertions, 3 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index cedafa008de5..7e7e61c00d61 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 */