[PATCH] Change the LLVM global lock to use RAII semantics

[Chandler Carruth]

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Comment at: lib/Support/Threading.cpp:25
@@ +24,3 @@
+sys::Mutex &llvm::llvm_get_global_lock() {
+  static sys::Mutex global_lock;
+  return global_lock;
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Is the constructor for a mutex threadsafe? Because we use VS versions which don't provide a thread safe initialization. Actually, even if the constructor is threadsafe, won't that still form a data race if we call this from two threads when built with MSVC?

I think you'll need this to be a static global ultimately... =/

http://reviews.llvm.org/D4142