[BP] MB-15292: Make CouchbaseAtomic::store() atomic

As identified by ThreadSantizer:

WARNING: ThreadSanitizer: data race (pid=59833)
  Write of size 8 at 0x7d240000d3f0 by thread T8:
    #0 CouchbaseAtomic<unsigned long>::store(unsigned long const&, memory_order) /root/couchbase-3.0/ep-engine/src/atomic.h:84 (ep.so+0x0000000414ef)
    #1 CouchbaseAtomic<unsigned long>::operator=(unsigned long const&) /root/couchbase-3.0/ep-engine/src/atomic.h:105 (ep.so+0x0000000401f5)
    #2 Warmup::scheduleEstimateDatabaseItemCount() /root/couchbase-3.0/ep-engine/src/warmup.cc:500 (ep.so+0x000000277991)
    #3 Warmup::step() /root/couchbase-3.0/ep-engine/src/warmup.cc:816 (ep.so+0x000000275124)
    #4 Warmup::transition(int, bool) /root/couchbase-3.0/ep-engine/src/warmup.cc:853 (ep.so+0x0000002754ff)
    #5 Warmup::createVBuckets(unsigned short) /root/couchbase-3.0/ep-engine/src/warmup.cc:491 (ep.so+0x00000027785f)
    #6 WarmupCreateVBuckets::run() /root/couchbase-3.0/ep-engine/src/warmup.h:234 (ep.so+0x00000028cde9)
    #7 ExecutorThread::run() /root/couchbase-3.0/ep-engine/src/executorthread.cc:110 (ep.so+0x0000001a2581)
    #8 launch_executor_thread(void*) /root/couchbase-3.0/ep-engine/src/executorthread.cc:34 (ep.so+0x0000001a1a5a)
    #9 platform_thread_wrap /root/couchbase-3.0/platform/src/cb_pthreads.c:19 (libplatform.so.0.1.0+0x000000002f14)

  Previous atomic write of size 8 at 0x7d240000d3f0 by main thread (mutexes: write M670470284968504712):
    #0 __tsan_atomic64_fetch_add <null>:0 (engine_testapp+0x00000008cb48)
    #1 CouchbaseAtomic<unsigned long>::load(memory_order) const /root/couchbase-3.0/ep-engine/src/atomic.h:77 (ep.so+0x0000000446b4)
    #2 CouchbaseAtomic<unsigned long>::operator unsigned long() const /root/couchbase-3.0/ep-engine/src/atomic.h:101 (ep.so+0x000000044575)
    #3 Warmup::addStats(void (*)(char const*, unsigned short, char const*, unsigned int, void const*), void const*) const /root/couchbase-3.0/ep-engine/src/warmup.cc:901 (ep.so+0x00000027d4ea)
    #4 EventuallyPersistentEngine::getStats(void const*, char const*, int, void (*)(char const*, unsigned short, char const*, unsigned int, void const*)) /root/couchbase-3.0/ep-engine/src/ep_engine.cc:4405 (ep.so+0x0000001155a9)
    #5 EvpGetStats(engine_interface*, void const*, char const*, int, void (*)(char const*, unsigned short, char const*, unsigned int, void const*)) /root/couchbase-3.0/ep-engine/src/ep_engine.cc:214 (ep.so+0x0000000fa102)
    #6 mock_get_stats /root/couchbase-3.0/memcached/programs/engine_testapp/engine_testapp.c:194 (engine_testapp+0x0000000aeecd)
    #7 wait_for_warmup_complete(engine_interface*, engine_interface_v1*) /root/couchbase-3.0/ep-engine/tests/ep_test_apis.cc:864 (ep_perfsuite.so+0x00000001b1cb)
    #8 test_setup(engine_interface*, engine_interface_v1*) /root/couchbase-3.0/ep-engine/tests/ep_testsuite_common.cc:128 (ep_perfsuite.so+0x00000000dc03)
    #9 execute_test /root/couchbase-3.0/memcached/programs/engine_testapp/engine_testapp.c:1037 (engine_testapp+0x0000000ab85a)
    #10 main /root/couchbase-3.0/memcached/programs/engine_testapp/engine_testapp.c:1296 (engine_testapp+0x0000000a9a19)

Change-Id: I260942712ca471c0d2e0fa3ebc4793d694f9b237
Reviewed-on: http://review.couchbase.org/51973
Tested-by: buildbot <[email protected]>
Reviewed-by: Jim Walker <[email protected]>
Reviewed-by: Chiyoung Seo <[email protected]>
Reviewed-on: http://review.couchbase.org/53502
Tested-by: Chiyoung Seo <[email protected]>

Author: daverigby

src/atomic.h

@@ -81,8 +81,7 @@ class CouchbaseAtomic {
 
     void store(const T &newValue, memory_order sync = memory_order_acq_rel) {
         (void) sync;
-        value = newValue;
-        ep_sync_synchronize();
+        ep_sync_lock_test_and_set(&value, newValue);
     }
 
 

tests/module_tests/atomic_test.cc

@@ -62,6 +62,17 @@ static void testAtomicInt() {
     cb_assert(intgen.latest() == (numThreads * numIterations));
 }
 
+static void testAtomicUint64() {
+    // Check that we can correctly load / store from values larger than 32bits.
+    AtomicValue<uint64_t> value;
+    uint64_t expected_val = 1ul << 33;
+    value.store(expected_val);
+    cb_assert(value == expected_val);
+
+    value.store(0);
+    cb_assert(value == 0);
+}
+
 static void testSetIfLess() {
     AtomicValue<int> x;
 
@@ -127,6 +138,7 @@ int testAtomicCompareExchangeStrong(void) {
 int main() {
     alarm(60);
     testAtomicInt();
+    testAtomicUint64();
     testSetIfLess();
     testSetIfBigger();
     testAtomicDouble();