[clang] [clang][modules][deps] Add mutex as an alternative to file lock (PR #129751)

[Michael Spencer via cfe-commits]

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@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_SERIALIZATION_MODULECACHELOCK_H
+#define LLVM_CLANG_SERIALIZATION_MODULECACHELOCK_H
+
+#include "clang/Basic/LLVM.h"
+#include "llvm/Support/LockFileManager.h"
+
+namespace clang {
+enum class LockResult { Owned, Shared, Error };
+enum class WaitForUnlockResult { Success, OwnerDied, Timeout };
+
+class ModuleCacheLockManager {
+public:
+  virtual operator LockResult() const = 0;
+  virtual WaitForUnlockResult waitForUnlock() = 0;
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Bigcheese wrote:

Looking more at how this is structured I think this should still have a timeout because of the LockFile implementation. And then it doesn't really hurt to actually do the timeout for the mutex impl, even though actually hitting that has other issues.

https://github.com/llvm/llvm-project/pull/129751