[libc-commits] [libc] [libc] rework mutex (PR #92168)

[Nick Desaulniers via libc-commits]

================
@@ -0,0 +1,78 @@
+//===-- Unittests for Linux's RawMutex ------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "include/llvm-libc-macros/linux/time-macros.h"
+#include "src/__support/CPP/atomic.h"
+#include "src/__support/OSUtil/syscall.h"
+#include "src/__support/threads/linux/raw_mutex.h"
+#include "src/__support/threads/sleep.h"
+#include "src/__support/time/linux/clock_gettime.h"
+#include "src/stdlib/exit.h"
+#include "src/sys/mman/mmap.h"
+#include "src/sys/mman/munmap.h"
+#include "test/UnitTest/Test.h"
+#include <sys/syscall.h>
+
+TEST(LlvmLibcSupportThreadsRawMutexTest, SmokeTest) {
+  LIBC_NAMESPACE::internal::RawMutex mutex;
+  ASSERT_TRUE(mutex.lock());
+  ASSERT_TRUE(mutex.unlock());
+  ASSERT_TRUE(mutex.try_lock());
+  ASSERT_FALSE(mutex.try_lock());
+  ASSERT_TRUE(mutex.unlock());
+  ASSERT_FALSE(mutex.unlock());
+}
+
+TEST(LlvmLibcSupportThreadsRawMutexTest, Timeout) {
+  LIBC_NAMESPACE::internal::RawMutex mutex;
+  ASSERT_TRUE(mutex.lock());
+  timespec ts;
+  LIBC_NAMESPACE::internal::clock_gettime(CLOCK_MONOTONIC, &ts);
+  ts.tv_sec += 1;
+  // Timeout will be respected when deadlock happens.
+  auto timeout = LIBC_NAMESPACE::internal::AbsTimeout::from_timespec(ts, false);
+  ASSERT_TRUE(timeout.has_value());
+  ASSERT_FALSE(mutex.lock(*timeout));
+  ASSERT_TRUE(mutex.unlock());
+  ASSERT_TRUE(mutex.lock(*timeout));
+  ASSERT_TRUE(mutex.unlock());
+  // If a lock can be acquired directly, expired timeout will not count.
+  ASSERT_TRUE(mutex.lock(*timeout));
+  ASSERT_TRUE(mutex.unlock());
+}
+
+TEST(LlvmLibcSupportThreadsRawMutexTest, PSharedLock) {
+  struct SharedData {
+    LIBC_NAMESPACE::internal::RawMutex mutex;
+    LIBC_NAMESPACE::cpp::Atomic<size_t> finished;
+    int data;
+  };
+  void *addr =
+      LIBC_NAMESPACE::mmap(nullptr, sizeof(SharedData), PROT_READ | PROT_WRITE,
+                           MAP_ANONYMOUS | MAP_SHARED, -1, 0);
+  ASSERT_NE(addr, MAP_FAILED);
+  auto *shared = reinterpret_cast<SharedData *>(addr);
+  shared->data = 0;
+  LIBC_NAMESPACE::internal::RawMutex::init(&shared->mutex);
+  // Avoid pull in our own implementation of pthread_t.
+  long pid = LIBC_NAMESPACE::syscall_impl<long>(SYS_fork);
+  for (int i = 0; i < 10000; ++i) {
+    shared->mutex.lock(LIBC_NAMESPACE::cpp::nullopt, true);
+    shared->data++;
+    shared->mutex.unlock(true);
+  }
+  // Mark the thread as finished.
+  shared->finished.fetch_add(1);
+  // early exit to avoid output pollution
----------------
nickdesaulniers wrote:

```suggestion
  // child early exit to avoid output pollution
```

https://github.com/llvm/llvm-project/pull/92168