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authorNathan Lynch <nathan_lynch@mentor.com>2015-08-07 21:03:23 -0500
committerCatalin Marinas <catalin.marinas@arm.com>2015-08-10 15:37:45 +0100
commit878854a374620a3f5e8c0a3c418e82a429bc2cff (patch)
treeedcf287f8f7829e25067bdda041cdcb53ef473ef /arch
parentf7644cbfcdf03528f0f450f3940c4985b2291f49 (diff)
downloadlinux-878854a374620a3f5e8c0a3c418e82a429bc2cff.tar.bz2
arm64: VDSO: fix coarse clock monotonicity regression
Since 906c55579a63 ("timekeeping: Copy the shadow-timekeeper over the real timekeeper last") it has become possible on arm64 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 arm64'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. Signed-off-by: Nathan Lynch <nathan_lynch@mentor.com> Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/kernel/vdso.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index ec37ab3f524f..97bc68f4c689 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -199,16 +199,15 @@ up_fail:
*/
void update_vsyscall(struct timekeeper *tk)
{
- struct timespec xtime_coarse;
u32 use_syscall = strcmp(tk->tkr_mono.clock->name, "arch_sys_counter");
++vdso_data->tb_seq_count;
smp_wmb();
- xtime_coarse = __current_kernel_time();
vdso_data->use_syscall = use_syscall;
- 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 = tk->tkr_mono.xtime_nsec >>
+ tk->tkr_mono.shift;
vdso_data->wtm_clock_sec = tk->wall_to_monotonic.tv_sec;
vdso_data->wtm_clock_nsec = tk->wall_to_monotonic.tv_nsec;