darion-yaphet commented on code in PR #3689:
URL: https://github.com/apache/brpc/pull/3689#discussion_r4412543210
##########
test/bthread_id_unittest.cpp:
##########
@@ -112,6 +114,37 @@ TEST(BthreadIdTest, join_before_destroy) {
ASSERT_EQ(1UL, non_null_ret);
}
+struct JoinRaceArgs {
+ bthread_id_t id;
+ std::atomic<bool> entered;
+};
+
+void* join_race_waiter(void* arg) {
+ JoinRaceArgs* args = static_cast<JoinRaceArgs*>(arg);
+ args->entered.store(true, std::memory_order_release);
Review Comment:
The waiting thread sets entered to true before calling bthread_id_join().
Therefore, the following sequence may occur:
1. The waiting thread sets entered = true and is then suspended by the
scheduler;
2. The main thread observes the flag and completes the locking and
destruction of the ID;
3. The waiting thread resumes, calls join() and immediately returns.
In this case, the test passes, but there is no target competition between
the reading of the butex_wait() status and the writing of the destruction
status.
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