From cc40f077b018e62e2e6f5dc279e3be84779569ce Mon Sep 17 00:00:00 2001
From: Owen Anderson <resistor@mac.com>
Date: Sat, 20 Jun 2009 00:27:21 +0000
Subject: [PATCH] Add debugging code to test for various locking faux-pas's,
 when running in single threaded mode.  This should help improve testing
 coverage for threading support, without having extensive actually concurrent
 clients yet.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73803 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/System/Mutex.h   | 17 ++++++++++++++++-
 include/llvm/System/RWMutex.h | 23 ++++++++++++++++++++++-
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/include/llvm/System/Mutex.h b/include/llvm/System/Mutex.h
index 0003ef881c8..d2c457dbc91 100644
--- a/include/llvm/System/Mutex.h
+++ b/include/llvm/System/Mutex.h
@@ -15,6 +15,7 @@
 #define LLVM_SYSTEM_MUTEX_H
 
 #include "llvm/System/Threading.h"
+#include <cassert>
 
 namespace llvm
 {
@@ -85,18 +86,32 @@ namespace llvm
     /// running in multithreaded mode.
     template<bool mt_only>
     class SmartMutex : public MutexImpl {
+      unsigned acquired;
+      bool recursive;
     public:
-      explicit SmartMutex(bool recursive = true) : MutexImpl(recursive) { }
+      explicit SmartMutex(bool rec = true) :
+        MutexImpl(rec), acquired(0), recursive(rec) { }
       
       bool acquire() {
         if (!mt_only || llvm_is_multithreaded())
           return MutexImpl::acquire();
+        
+        // Single-threaded debugging code.  This would be racy in multithreaded
+        // mode, but provides not sanity checks in single threaded mode.
+        assert((recursive || acquired == 0) && "Lock already acquired!!");
+        ++acquired;
         return true;
       }
 
       bool release() {
         if (!mt_only || llvm_is_multithreaded())
           return MutexImpl::release();
+        
+        // Single-threaded debugging code.  This would be racy in multithreaded
+        // mode, but provides not sanity checks in single threaded mode.
+        assert(((recursive && acquired) || (acquired == 1)) &&
+               "Lock not acquired before release!");
+        --acquired;
         return true;
       }
 
diff --git a/include/llvm/System/RWMutex.h b/include/llvm/System/RWMutex.h
index aa5b0b946aa..e577d457afb 100644
--- a/include/llvm/System/RWMutex.h
+++ b/include/llvm/System/RWMutex.h
@@ -15,6 +15,7 @@
 #define LLVM_SYSTEM_RWMUTEX_H
 
 #include "llvm/System/Threading.h"
+#include <cassert>
 
 namespace llvm
 {
@@ -84,30 +85,50 @@ namespace llvm
     /// running in multithreaded mode.
     template<bool mt_only>
     class SmartRWMutex : public RWMutexImpl {
+      unsigned readers, writers;
     public:
-      explicit SmartRWMutex() : RWMutexImpl() { }
+      explicit SmartRWMutex() : RWMutexImpl(), readers(0), writers(0) { }
       
       bool reader_acquire() {
         if (!mt_only || llvm_is_multithreaded())
           return RWMutexImpl::reader_acquire();
+        
+        // Single-threaded debugging code.  This would be racy in multithreaded
+        // mode, but provides not sanity checks in single threaded mode.
+        ++readers;
         return true;
       }
       
       bool reader_release() {
         if (!mt_only || llvm_is_multithreaded())
           return RWMutexImpl::reader_release();
+        
+        // Single-threaded debugging code.  This would be racy in multithreaded
+        // mode, but provides not sanity checks in single threaded mode.
+        assert(readers > 0 && "Reader lock not acquired before release!");
+        --readers;
         return true;
       }
       
       bool writer_acquire() {
         if (!mt_only || llvm_is_multithreaded())
           return RWMutexImpl::writer_acquire();
+        
+        // Single-threaded debugging code.  This would be racy in multithreaded
+        // mode, but provides not sanity checks in single threaded mode.
+        assert(writers == 0 && "Writer lock already acquired!");
+        ++writers;
         return true;
       }
       
       bool writer_release() {
         if (!mt_only || llvm_is_multithreaded())
           return RWMutexImpl::writer_release();
+        
+        // Single-threaded debugging code.  This would be racy in multithreaded
+        // mode, but provides not sanity checks in single threaded mode.
+        assert(writers == 1 && "Writer lock not acquired before release!");
+        --writers;
         return true;
       }