--- /dev/null
+// Stress test for https://reviews.llvm.org/D101881
+// RUN: %clangxx_hwasan -DREUSE=0 %s -pthread -O2 -o %t && %run %t 2>&1
+// RUN: %clangxx_hwasan -DREUSE=1 %s -pthread -O2 -o %t_reuse && %run %t_reuse 2>&1
+
+#include <thread>
+#include <vector>
+
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <stdio.h>
+
+constexpr int kTopThreads = 20;
+constexpr int kChildThreads = 30;
+constexpr int kChildIterations = REUSE ? 8 : 1;
+
+constexpr int kProcessIterations = 20;
+
+void Thread() {
+ for (int i = 0; i < kChildIterations; ++i) {
+ std::vector<std::thread> threads;
+ for (int i = 0; i < kChildThreads; ++i)
+ threads.emplace_back([]() {});
+ for (auto &t : threads)
+ t.join();
+ }
+}
+
+void run() {
+ std::vector<std::thread> threads;
+ for (int i = 0; i < kTopThreads; ++i)
+ threads.emplace_back(Thread);
+ for (auto &t : threads)
+ t.join();
+}
+
+int main() {
+#if REUSE
+ // Test thread reuse with multiple iterations of thread create / join in a single process.
+ run();
+#else
+ // Test new, non-reused thread creation by running a single iteration of create / join in a freshly started process.
+ for (int i = 0; i < kProcessIterations; ++i) {
+ int pid = fork();
+ if (pid) {
+ int wstatus;
+ do {
+ waitpid(pid, &wstatus, 0);
+ } while (!WIFEXITED(wstatus) && !WIFSIGNALED(wstatus));
+ if (!WIFEXITED(wstatus) || WEXITSTATUS(wstatus)) {
+ fprintf(stderr, "failed at iteration %d / %d\n", i, kProcessIterations);
+ return 1;
+ }
+ } else {
+ run();
+ return 0;
+ }
+ }
+#endif
+}