1 files changed, 47 insertions, 0 deletions
diff --git a/libc/src/pthread/pthread_spin_lock.cpp b/libc/src/pthread/pthread_spin_lock.cpp
new file mode 100644
index 000000000000..61c8db14e487
--- /dev/null
+++ b/libc/src/pthread/pthread_spin_lock.cpp
@@ -0,0 +1,47 @@
+//===-- Implementation of pthread_spin_lock function ----------------------===//
+//
+// 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 "src/pthread/pthread_spin_lock.h"
+#include "hdr/errno_macros.h"
+#include "src/__support/common.h"
+#include "src/__support/threads/identifier.h"
+#include "src/__support/threads/spin_lock.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+static_assert(sizeof(pthread_spinlock_t::__lockword) == sizeof(SpinLock) &&
+                  alignof(decltype(pthread_spinlock_t::__lockword)) ==
+                      alignof(SpinLock),
+              "pthread_spinlock_t::__lockword and SpinLock must be of the same "
+              "size and alignment");
+
+LLVM_LIBC_FUNCTION(int, pthread_spin_lock, (pthread_spinlock_t * lock)) {
+  // If an implementation detects that the value specified by the lock argument
+  // to pthread_spin_lock() or pthread_spin_trylock() does not refer to an
+  // initialized spin lock object, it is recommended that the function should
+  // fail and report an [EINVAL] error.
+  if (!lock)
+    return EINVAL;
+  auto spin_lock = reinterpret_cast<SpinLock *>(&lock->__lockword);
+  if (spin_lock->is_invalid())
+    return EINVAL;
+
+  pid_t self_tid = internal::gettid();
+  // If an implementation detects that the value specified by the lock argument
+  // to pthread_spin_lock() refers to a spin lock object for which the calling
+  // thread already holds the lock, it is recommended that the function should
+  // fail and report an [EDEADLK] error.
+  if (lock->__owner == self_tid)
+    return EDEADLK;
+
+  spin_lock->lock();
+  lock->__owner = self_tid;
+  return 0;
+}
+
+} // namespace LIBC_NAMESPACE_DECL