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Merge pull request #14227 from ivancich/wip-perf-counter-race

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common/perf_counters: fix race condition with atomic variables

Reviewed-by: Sage Weil <sage@redhat.com>
Reviewed-by: Josh Durgin <jdurgin@redhat.com>
This commit is contained in:
Sage Weil 2017-04-08 09:22:53 -05:00 committed by GitHub
commit bcb17aa093
1 changed files with 5 additions and 3 deletions
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8
src/common/perf_counters.h
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@ -120,13 +120,15 @@ public:
}
}
/// read <sum, count> safely
// read <sum, count> safely by making sure the post- and pre-count
// are identical; in other words the whole loop needs to be run
// without any intervening calls to inc, set, or tinc.
pair<uint64_t,uint64_t> read_avg() const {
uint64_t sum, count;
do {
count = avgcount.read();
count = avgcount2.read();
sum = u64.read();
} while (avgcount2.read() != count);
} while (avgcount.read() != count);
return make_pair(sum, count);
}
};