• John Stultz's avatar
    time: Fix CLOCK_MONOTONIC_RAW sub-nanosecond accounting · 3d88d56c
    John Stultz authored
    Due to how the MONOTONIC_RAW accumulation logic was handled,
    there is the potential for a 1ns discontinuity when we do
    accumulations. This small discontinuity has for the most part
    gone un-noticed, but since ARM64 enabled CLOCK_MONOTONIC_RAW
    in their vDSO clock_gettime implementation, we've seen failures
    with the inconsistency-check test in kselftest.
    
    This patch addresses the issue by using the same sub-ns
    accumulation handling that CLOCK_MONOTONIC uses, which avoids
    the issue for in-kernel users.
    
    Since the ARM64 vDSO implementation has its own clock_gettime
    calculation logic, this patch reduces the frequency of errors,
    but failures are still seen. The ARM64 vDSO will need to be
    updated to include the sub-nanosecond xtime_nsec values in its
    calculation for this issue to be completely fixed.
    Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
    Tested-by: default avatarDaniel Mentz <danielmentz@google.com>
    Cc: Prarit Bhargava <prarit@redhat.com>
    Cc: Kevin Brodsky <kevin.brodsky@arm.com>
    Cc: Richard Cochran <richardcochran@gmail.com>
    Cc: Stephen Boyd <stephen.boyd@linaro.org>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: "stable #4 . 8+" <stable@vger.kernel.org>
    Cc: Miroslav Lichvar <mlichvar@redhat.com>
    Link: http://lkml.kernel.org/r/1496965462-20003-3-git-send-email-john.stultz@linaro.orgSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    3d88d56c
timekeeping.c 64.5 KB