From: Will Deacon <will.deacon@xxxxxxx>
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.
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
Cc: Richard Cochran <richardcochran@xxxxxxxxx>
Cc: Prarit Bhargava <prarit@xxxxxxxxxx>
Cc: Stephen Boyd <stephen.boyd@xxxxxxxxxx>
Cc: Kevin Brodsky <kevin.brodsky@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Daniel Mentz <danielmentz@xxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx> #4.8+
Reported-by: John Stultz <john.stultz@xxxxxxxxxx>
Acked-by: Kevin Brodsky <kevin.brodsky@xxxxxxx>
Tested-by: Daniel Mentz <danielmentz@xxxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
[jstultz: minor whitespace tweak, tried to improve commit
message to make it more clear this fixes a regression]
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
v2: Tweak commit message to address Ingo's feedback
---
arch/arm64/kernel/vdso.c | 5 +++--
arch/arm64/kernel/vdso/gettimeofday.S | 1 -
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 41b6e31..d0cb007 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -221,10 +221,11 @@ void update_vsyscall(struct timekeeper *tk)
/* tkr_mono.cycle_last == tkr_raw.cycle_last */
vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last;
vdso_data->raw_time_sec = tk->raw_time.tv_sec;
- vdso_data->raw_time_nsec = tk->raw_time.tv_nsec;
+ vdso_data->raw_time_nsec = (tk->raw_time.tv_nsec <<
+ tk->tkr_raw.shift) +
+ tk->tkr_raw.xtime_nsec;
vdso_data->xtime_clock_sec = tk->xtime_sec;
vdso_data->xtime_clock_nsec = tk->tkr_mono.xtime_nsec;
- /* tkr_raw.xtime_nsec == 0 */
vdso_data->cs_mono_mult = tk->tkr_mono.mult;
vdso_data->cs_raw_mult = tk->tkr_raw.mult;
/* tkr_mono.shift == tkr_raw.shift */
diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S
index e00b467..76320e9 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
--
2.7.4