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Count threads after thread-creation while still holding mutex lock

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The `Mutex` is locked with the `MutexLock` before spawning the thread, so that the thread is prevented from completing (by being blocked on `Mutex`) before the new thread count is obtained. However, the existing bug (introduced in 22e6055) releases `Mutex` before obtaining the new thread count, which allows the thread to run to completion in the meantime.

Also, since the `(thread_count_after_create != starting_count + 1)` condition (line 328) skips the remainder of the `for`-loop body on every iteration, `thread_count_after_join` stays uninitialized.

I believe this is why [this test failed][1] on the macOS CI with this trace:

```
[----------] 1 test from GetThreadCountTest
[ RUN      ] GetThreadCountTest.ReturnsCorrectValue
googletest/test/googletest-port-test.cc:350: Failure
Expected equality of these values:
  thread_count_after_create
    Which is: 1
  starting_count + 1
    Which is: 2

googletest/test/googletest-port-test.cc:351: Failure
Expected equality of these values:
  thread_count_after_join
    Which is: 140493185949400
  starting_count
    Which is: 1

[  FAILED  ] GetThreadCountTest.ReturnsCorrectValue (2 ms)
[----------] 1 test from GetThreadCountTest (2 ms total)
```

[1]: https://github.com/google/googletest/actions/runs/6064919420/job/16453860690?pr=3049
This commit is contained in:
Tanzinul Islam 2023-09-03 15:39:19 +01:00 committed by Tanzinul Islam
parent 8a6feabf04
commit b86bf840d1
1 changed files with 3 additions and 3 deletions
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4
googletest/test/googletest-port-test.cc
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@ -296,7 +296,7 @@ void* ThreadFunc(void* data) {
TEST(GetThreadCountTest, ReturnsCorrectValue) { TEST(GetThreadCountTest, ReturnsCorrectValue) {
size_t starting_count; size_t starting_count;
size_t thread_count_after_create; size_t thread_count_after_create;
size_t thread_count_after_join; size_t thread_count_after_join = 0;
// We can't guarantee that no other thread was created or destroyed between // We can't guarantee that no other thread was created or destroyed between
// any two calls to GetThreadCount(). We make multiple attempts, hoping that // any two calls to GetThreadCount(). We make multiple attempts, hoping that
@ -316,9 +316,9 @@ TEST(GetThreadCountTest, ReturnsCorrectValue) {
const int status = pthread_create(&thread_id, &attr, &ThreadFunc, &mutex); const int status = pthread_create(&thread_id, &attr, &ThreadFunc, &mutex);
ASSERT_EQ(0, pthread_attr_destroy(&attr)); ASSERT_EQ(0, pthread_attr_destroy(&attr));
ASSERT_EQ(0, status); ASSERT_EQ(0, status);
}
thread_count_after_create = GetThreadCount(); thread_count_after_create = GetThreadCount();
}
void* dummy; void* dummy;
ASSERT_EQ(0, pthread_join(thread_id, &dummy)); ASSERT_EQ(0, pthread_join(thread_id, &dummy));