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authorWill Deacon <will.deacon@arm.com>2017-06-09 02:44:22 +0300
committerThomas Gleixner <tglx@linutronix.de>2017-06-20 11:41:51 +0300
commitdbb236c1ceb697a559e0694ac4c9e7b9131d0b16 (patch)
tree171280b1a599f77933532dda1695f07074b9342f /arch/arm64/kernel/vdso.c
parent3d88d56c5873f6eebe23e05c3da701960146b801 (diff)
downloadlinux-dbb236c1ceb697a559e0694ac4c9e7b9131d0b16.tar.xz
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.c')
-rw-r--r--arch/arm64/kernel/vdso.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 41b6e31f8f55..d0cb007fa482 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 */