chenBright commented on code in PR #3637:
URL: https://github.com/apache/brpc/pull/3637#discussion_r4336171821
##########
test/bthread_futex_unittest.cpp:
##########
@@ -115,6 +117,100 @@ TEST(FutexTest, futex_wake_before_wait) {
ASSERT_EQ(ETIMEDOUT, errno);
}
+struct WakeCountWaiterArg {
+ butil::atomic<int>* word;
+ butil::atomic<bool>* finished;
+ int rc;
+ int error;
+};
+
+void* wake_count_waiter(void* void_arg) {
+ WakeCountWaiterArg* arg = static_cast<WakeCountWaiterArg*>(void_arg);
+ const timespec timeout = { 2, 0 };
+ arg->rc = bthread::futex_wait_private(arg->word, 0, &timeout);
+ arg->error = errno;
+ arg->finished->store(true, butil::memory_order_release);
+ return nullptr;
+}
+
+// A successful wake confirms that the waiter was registered. The waiter never
+// waits again, so every subsequent wake must return zero, even before it runs.
+// Repeat to exercise both orders of reacquiring the simulated futex's mutex.
+void check_wake_count_after_notification(bool expire_another_waiter) {
+ int notified = 0;
+ for (int i = 0; i < 256; ++i) {
+ butil::atomic<int> word(0);
+ butil::atomic<bool> finished(false);
+ WakeCountWaiterArg arg = { &word, &finished, -1, 0 };
+ pthread_t waiter;
+ ASSERT_EQ(0, pthread_create(&waiter, nullptr, wake_count_waiter,
&arg));
+
+ int first_wake = 0;
+ const int64_t deadline = butil::cpuwide_time_us() + 5000000L;
+ do {
+ first_wake = bthread::futex_wake_private(&word, 1);
+ if (first_wake != 0 || finished.load(butil::memory_order_acquire))
{
+ break;
+ }
+ sched_yield();
+ } while (butil::cpuwide_time_us() < deadline);
Review Comment:
Addressed in e73372f.
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