Commit-ID: dbb236c1ceb697a559e0694ac4c9e7b9131d0b16 Gitweb: http://git.kernel.org/tip/dbb236c1ceb697a559e0694ac4c9e7b9131d0b16 Author: Will Deacon <will.deacon@xxxxxxx> AuthorDate: Thu, 8 Jun 2017 16:44:22 -0700 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitDate: Tue, 20 Jun 2017 10:41:51 +0200 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@xxxxxxxxxx> Signed-off-by: Will Deacon <will.deacon@xxxxxxx> Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx> Tested-by: Daniel Mentz <danielmentz@xxxxxxxxxx> Acked-by: Kevin Brodsky <kevin.brodsky@xxxxxxx> Cc: Prarit Bhargava <prarit@xxxxxxxxxx> Cc: Richard Cochran <richardcochran@xxxxxxxxx> Cc: Stephen Boyd <stephen.boyd@xxxxxxxxxx> Cc: "stable #4 . 8+" <stable@xxxxxxxxxxxxxxx> Cc: Miroslav Lichvar <mlichvar@xxxxxxxxxx> Link: http://lkml.kernel.org/r/1496965462-20003-4-git-send-email-john.stultz@xxxxxxxxxx Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> --- 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