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author | Nathan Lynch <nathan_lynch@mentor.com> | 2015-08-10 17:36:06 +0100 |
---|---|---|
committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2015-08-11 13:42:44 +0100 |
commit | 09edea4f8fdeb4e292b80d493296070f5ec64e6e (patch) | |
tree | 4215bd594495bc36545a4e092474977ebc44a1e8 /arch/arm | |
parent | e83dd3770021910293edea6fb2dc2fa306b1bf34 (diff) | |
download | linux-stable-09edea4f8fdeb4e292b80d493296070f5ec64e6e.tar.gz linux-stable-09edea4f8fdeb4e292b80d493296070f5ec64e6e.tar.bz2 linux-stable-09edea4f8fdeb4e292b80d493296070f5ec64e6e.zip |
ARM: 8410/1: VDSO: fix coarse clock monotonicity regression
Since 906c55579a63 ("timekeeping: Copy the shadow-timekeeper over the
real timekeeper last") it has become possible on ARM to:
- Obtain a CLOCK_MONOTONIC_COARSE or CLOCK_REALTIME_COARSE timestamp
via syscall.
- Subsequently obtain a timestamp for the same clock ID via VDSO which
predates the first timestamp (by one jiffy).
This is because ARM's update_vsyscall is deriving the coarse time
using the __current_kernel_time interface, when it should really be
using the timekeeper object provided to it by the timekeeping core.
It happened to work before only because __current_kernel_time would
access the same timekeeper object which had been passed to
update_vsyscall. This is no longer the case.
Cc: stable@vger.kernel.org
Fixes: 906c55579a63 ("timekeeping: Copy the shadow-timekeeper over the real timekeeper last")
Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm')
-rw-r--r-- | arch/arm/kernel/vdso.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c index efe17dd9b921..54a5aeab988d 100644 --- a/arch/arm/kernel/vdso.c +++ b/arch/arm/kernel/vdso.c @@ -296,7 +296,6 @@ static bool tk_is_cntvct(const struct timekeeper *tk) */ void update_vsyscall(struct timekeeper *tk) { - struct timespec xtime_coarse; struct timespec64 *wtm = &tk->wall_to_monotonic; if (!cntvct_ok) { @@ -308,10 +307,10 @@ void update_vsyscall(struct timekeeper *tk) vdso_write_begin(vdso_data); - xtime_coarse = __current_kernel_time(); vdso_data->tk_is_cntvct = tk_is_cntvct(tk); - vdso_data->xtime_coarse_sec = xtime_coarse.tv_sec; - vdso_data->xtime_coarse_nsec = xtime_coarse.tv_nsec; + vdso_data->xtime_coarse_sec = tk->xtime_sec; + vdso_data->xtime_coarse_nsec = (u32)(tk->tkr_mono.xtime_nsec >> + tk->tkr_mono.shift); vdso_data->wtm_clock_sec = wtm->tv_sec; vdso_data->wtm_clock_nsec = wtm->tv_nsec; |