From a47d0a0dd4ef6b11495522c8669271cc3c761c63 Mon Sep 17 00:00:00 2001
From: ludehp <ludehp@163.com>
Date: Sun, 2 Dec 2018 23:01:51 +0800
Subject: [PATCH] common: fix a racing in
 PerfCounters::perf_counter_data_any_d::read_avg

Fixes: http://tracker.ceph.com/issues/25211

Signed-off-by: ludehp <ludehp@163.com>
---
 src/common/perf_counters.h |  4 ++--
 src/test/perf_counters.cc  | 46 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/src/common/perf_counters.h b/src/common/perf_counters.h
index 0b9f782bc9e3d..d65af189f5671 100644
--- a/src/common/perf_counters.h
+++ b/src/common/perf_counters.h
@@ -204,9 +204,9 @@ public:
     pair<uint64_t,uint64_t> read_avg() const {
       uint64_t sum, count;
       do {
-	count = avgcount;
+	count = avgcount2;
 	sum = u64;
-      } while (avgcount2 != count);
+      } while (avgcount != count);
       return make_pair(sum, count);
     }
   };
diff --git a/src/test/perf_counters.cc b/src/test/perf_counters.cc
index 87ce7163cdead..a3a5a52782b37 100644
--- a/src/test/perf_counters.cc
+++ b/src/test/perf_counters.cc
@@ -42,6 +42,7 @@
 #include <sys/un.h>
 #include <time.h>
 #include <unistd.h>
+#include <thread>
 
 #include "common/common_init.h"
 
@@ -219,3 +220,48 @@ TEST(PerfCounters, ResetPerfCounters) {
   ASSERT_EQ("", client.do_request("{ \"prefix\": \"perf reset\", \"var\": \"test_perfcounter_1\", \"format\": \"json\" }", &msg));
   ASSERT_EQ(sd("{\"error\":\"Not find: test_perfcounter_1\"}"), msg);
 }
+
+enum {
+  TEST_PERFCOUNTERS3_ELEMENT_FIRST = 400,
+  TEST_PERFCOUNTERS3_ELEMENT_READ,
+  TEST_PERFCOUNTERS3_ELEMENT_LAST,
+};
+
+static std::shared_ptr<PerfCounters> setup_test_perfcounter3(CephContext* cct) {
+  PerfCountersBuilder bld(cct, "test_percounter_3",
+      TEST_PERFCOUNTERS3_ELEMENT_FIRST, TEST_PERFCOUNTERS3_ELEMENT_LAST);
+  bld.add_time_avg(TEST_PERFCOUNTERS3_ELEMENT_READ, "read_avg");
+  std::shared_ptr<PerfCounters> p(bld.create_perf_counters());
+  return p;
+}
+
+static void counters_inc_test(std::shared_ptr<PerfCounters> fake_pf) {
+  int i = 100000;
+  utime_t t;
+
+  // set to 1 nsec
+  t.set_from_double(0.000000001);
+  while (i--) {
+    // increase by one, make sure data.u64 equal to data.avgcount
+    fake_pf->tinc(TEST_PERFCOUNTERS3_ELEMENT_READ, t);
+  }
+}
+
+static void counters_readavg_test(std::shared_ptr<PerfCounters> fake_pf) {
+  int i = 100000;
+
+  while (i--) {
+    std::pair<uint64_t, uint64_t> dat = fake_pf->get_tavg_ns(TEST_PERFCOUNTERS3_ELEMENT_READ);
+    // sum and count should be identical as we increment TEST_PERCOUNTERS_ELEMENT_READ by 1 nsec eveytime
+    ASSERT_EQ(dat.first, dat.second);
+  }
+}
+
+TEST(PerfCounters, read_avg) {
+  std::shared_ptr<PerfCounters> fake_pf = setup_test_perfcounter3(g_ceph_context);
+
+  std::thread t1(counters_inc_test, fake_pf);
+  std::thread t2(counters_readavg_test, fake_pf);
+  t2.join();
+  t1.join();
+}
\ No newline at end of file
-- 
2.39.5