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authorThomas Gleixner <tglx@linutronix.de>2014-09-06 14:24:49 +0400
committerThomas Gleixner <tglx@linutronix.de>2014-09-06 14:58:18 +0400
commit9bf2419fa7bffa16ce58a4d5c20399eff8c970c9 (patch)
tree23415c1be550979e70c5ecabff7a76aff47ee378 /kernel/time
parent849151dd5481bc8acb1d287a299b5d6a4ca9f1c3 (diff)
downloadlinux-9bf2419fa7bffa16ce58a4d5c20399eff8c970c9.tar.xz
timekeeping: Update timekeeper before updating vsyscall and pvclock
The update_walltime() code works on the shadow timekeeper to make the seqcount protected region as short as possible. But that update to the shadow timekeeper does not update all timekeeper fields because it's sufficient to do that once before it becomes life. One of these fields is tkr.base_mono. That stays stale in the shadow timekeeper unless an operation happens which copies the real timekeeper to the shadow. The update function is called after the update calls to vsyscall and pvclock. While not correct, it did not cause any problems because none of the invoked update functions used base_mono. commit cbcf2dd3b3d4 (x86: kvm: Make kvm_get_time_and_clockread() nanoseconds based) changed that in the kvm pvclock update function, so the stale mono_base value got used and caused kvm-clock to malfunction. Put the update where it belongs and fix the issue. Reported-by: Chris J Arges <chris.j.arges@canonical.com> Reported-by: Paolo Bonzini <pbonzini@redhat.com> Cc: Gleb Natapov <gleb@kernel.org> Cc: John Stultz <john.stultz@linaro.org> Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1409050000570.3333@nanos Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/timekeeping.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index fb4a9c2cf8d9..ec1791fae965 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -442,11 +442,12 @@ static void timekeeping_update(struct timekeeper *tk, unsigned int action)
tk->ntp_error = 0;
ntp_clear();
}
- update_vsyscall(tk);
- update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
tk_update_ktime_data(tk);
+ update_vsyscall(tk);
+ update_pvclock_gtod(tk, action & TK_CLOCK_WAS_SET);
+
if (action & TK_MIRROR)
memcpy(&shadow_timekeeper, &tk_core.timekeeper,
sizeof(tk_core.timekeeper));