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| author | Will Deacon <will.deacon@arm.com> | 2017-06-09 01:44:22 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2017-06-20 10:41:51 +0200 |
| commit | dbb236c1ceb697a559e0694ac4c9e7b9131d0b16 (patch) | |
| tree | 171280b1a599f77933532dda1695f07074b9342f /arch/arm64/kernel/vdso | |
| parent | time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond accounting (diff) | |
| download | linux-dbb236c1ceb697a559e0694ac4c9e7b9131d0b16.tar.xz linux-dbb236c1ceb697a559e0694ac4c9e7b9131d0b16.zip | |
arm64/vdso: Fix nsec handling for CLOCK_MONOTONIC_RAW
Recently vDSO support for CLOCK_MONOTONIC_RAW was added in
49eea433b326 ("arm64: Add support for CLOCK_MONOTONIC_RAW in
clock_gettime() vDSO"). Noticing that the core timekeeping code
never set tkr_raw.xtime_nsec, the vDSO implementation didn't
bother exposing it via the data page and instead took the
unshifted tk->raw_time.tv_nsec value which was then immediately
shifted left in the vDSO code.
Unfortunately, by accellerating the MONOTONIC_RAW clockid, it
uncovered potential 1ns time inconsistencies caused by the
timekeeping core not handing sub-ns resolution.
Now that the core code has been fixed and is actually setting
tkr_raw.xtime_nsec, we need to take that into account in the
vDSO by adding it to the shifted raw_time value, in order to
fix the user-visible inconsistency. Rather than do that at each
use (and expand the data page in the process), instead perform
the shift/addition operation when populating the data page and
remove the shift from the vDSO code entirely.
[jstultz: minor whitespace tweak, tried to improve commit
message to make it more clear this fixes a regression]
Reported-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Tested-by: Daniel Mentz <danielmentz@google.com>
Acked-by: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Stephen Boyd <stephen.boyd@linaro.org>
Cc: "stable #4 . 8+" <stable@vger.kernel.org>
Cc: Miroslav Lichvar <mlichvar@redhat.com>
Link: http://lkml.kernel.org/r/1496965462-20003-4-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/arm64/kernel/vdso')
| -rw-r--r-- | arch/arm64/kernel/vdso/gettimeofday.S | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S index e00b4671bd7c..76320e920965 100644 --- a/arch/arm64/kernel/vdso/gettimeofday.S +++ b/arch/arm64/kernel/vdso/gettimeofday.S @@ -256,7 +256,6 @@ monotonic_raw: seqcnt_check fail=monotonic_raw /* All computations are done with left-shifted nsecs. */ - lsl x14, x14, x12 get_nsec_per_sec res=x9 lsl x9, x9, x12 |