From dbb236c1ceb697a559e0694ac4c9e7b9131d0b16 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 8 Jun 2017 16:44:22 -0700 Subject: 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 Signed-off-by: Will Deacon Signed-off-by: John Stultz Tested-by: Daniel Mentz Acked-by: Kevin Brodsky Cc: Prarit Bhargava Cc: Richard Cochran Cc: Stephen Boyd Cc: "stable #4 . 8+" Cc: Miroslav Lichvar Link: http://lkml.kernel.org/r/1496965462-20003-4-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner --- arch/arm64/kernel/vdso/gettimeofday.S | 1 - 1 file changed, 1 deletion(-) (limited to 'arch/arm64/kernel/vdso/gettimeofday.S') 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 -- cgit v1.2.3-55-g7522