47 lines
1.5 KiB
Diff
47 lines
1.5 KiB
Diff
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diff -ru -x '*~' linux-2.6.32.24-orig/arch/x86/kernel/pvclock.c linux-2.6.32.24/arch/x86/kernel/pvclock.c
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--- linux-2.6.32.24-orig/arch/x86/kernel/pvclock.c 2010-10-01 22:51:56.000000000 +0200
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+++ linux-2.6.32.24/arch/x86/kernel/pvclock.c 2010-10-25 14:02:14.000000000 +0200
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@@ -109,14 +109,11 @@
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return pv_tsc_khz;
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}
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-static atomic64_t last_value = ATOMIC64_INIT(0);
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-
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cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
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{
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struct pvclock_shadow_time shadow;
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unsigned version;
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cycle_t ret, offset;
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- u64 last;
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do {
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version = pvclock_get_time_values(&shadow, src);
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@@ -126,27 +123,6 @@
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barrier();
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} while (version != src->version);
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- /*
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- * Assumption here is that last_value, a global accumulator, always goes
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- * forward. If we are less than that, we should not be much smaller.
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- * We assume there is an error marging we're inside, and then the correction
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- * does not sacrifice accuracy.
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- *
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- * For reads: global may have changed between test and return,
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- * but this means someone else updated poked the clock at a later time.
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- * We just need to make sure we are not seeing a backwards event.
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- *
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- * For updates: last_value = ret is not enough, since two vcpus could be
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- * updating at the same time, and one of them could be slightly behind,
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- * making the assumption that last_value always go forward fail to hold.
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- */
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- last = atomic64_read(&last_value);
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- do {
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- if (ret < last)
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- return last;
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- last = atomic64_cmpxchg(&last_value, last, ret);
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- } while (unlikely(last != ret));
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-
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return ret;
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}
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