]> git.ipfire.org Git - people/arne_f/kernel.git/commit
arm64/vdso: Fix nsec handling for CLOCK_MONOTONIC_RAW
authorWill Deacon <will.deacon@arm.com>
Thu, 8 Jun 2017 23:44:22 +0000 (16:44 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 29 Jun 2017 11:00:30 +0000 (13:00 +0200)
commit99f66b5182a4f3d89563634f2fe156d4629b9c10
tree6d2c407fbf624bec9bcbd285ade82e06a55a972e
parenta53bfdda06ac114c42796b4193aee10a8108bca1
arm64/vdso: Fix nsec handling for CLOCK_MONOTONIC_RAW

commit dbb236c1ceb697a559e0694ac4c9e7b9131d0b16 upstream.

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: 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arch/arm64/kernel/vdso.c
arch/arm64/kernel/vdso/gettimeofday.S