From b8a2f0495e6ecd4ac379e91fb88531bbeeceb46d Mon Sep 17 00:00:00 2001
From: Jeff Hill <johill@lanl.gov>
Date: Wed, 16 Apr 2003 20:55:41 +0000
Subject: [PATCH] evaluation version of deadlock detect mutex

---
 src/libCom/osi/epicsMutex.cpp | 52 +++++++++++++++++++++++++++++++++++
 src/libCom/osi/epicsMutex.h   | 21 ++++++++++++--
 2 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/src/libCom/osi/epicsMutex.cpp b/src/libCom/osi/epicsMutex.cpp
index 4ee460580..94c7cfb62 100644
--- a/src/libCom/osi/epicsMutex.cpp
+++ b/src/libCom/osi/epicsMutex.cpp
@@ -235,4 +235,56 @@ void epicsMutex :: show ( unsigned level ) const
     epicsMutexShow ( this->id, level );
 }
 
+static epicsThreadPrivate < epicsDeadlockDetectMutex >  
+    currentMutexLevel;
+
+epicsDeadlockDetectMutex::
+    epicsDeadlockDetectMutex ( hierarchyLevel_t level ) : 
+    hierarchyLevel ( level ), pPreviousLevel ( 0 )
+{
+}
+
+epicsDeadlockDetectMutex::~epicsDeadlockDetectMutex ()
+{
+}
+
+void epicsDeadlockDetectMutex::show ( unsigned level ) const
+{
+    this->mutex.show ( level );
+}
+
+void epicsDeadlockDetectMutex::lock ()
+{
+    epicsDeadlockDetectMutex * pPrev = currentMutexLevel.get();
+    if ( pPrev && pPrev != this ) {
+        if ( pPrev->hierarchyLevel >= this->hierarchyLevel ) {
+            errlogPrintf ( "!!!! Deadlock Vulnerability Detected !!!! "
+                "at level %u and moving to level %u\n",
+                pPrev->hierarchyLevel,
+                this->hierarchyLevel );
+        }
+    }
+    this->mutex.lock ();
+    if ( pPrev && pPrev != this ) {
+        currentMutexLevel.set ( this );
+        this->pPreviousLevel = pPrev;
+    }
+}
+
+void epicsDeadlockDetectMutex::unlock ()
+{
+    currentMutexLevel.set ( this->pPreviousLevel );
+    this->mutex.unlock ();
+}
+
+bool epicsDeadlockDetectMutex::tryLock ()
+{
+    bool success = this->mutex.tryLock ();
+    if ( success ) {
+        this->pPreviousLevel = currentMutexLevel.get();
+        currentMutexLevel.set ( this );
+    }
+    return success;
+}
+
 
diff --git a/src/libCom/osi/epicsMutex.h b/src/libCom/osi/epicsMutex.h
index 883c5bcd7..1bce729d3 100644
--- a/src/libCom/osi/epicsMutex.h
+++ b/src/libCom/osi/epicsMutex.h
@@ -25,8 +25,8 @@ typedef enum {
 
 class epicsShareClass epicsMutex {
 public:
-    class mutexCreateFailed {}; // exception
-    class invalidMutex {}; // exception
+    class mutexCreateFailed {}; /* exception */
+    class invalidMutex {}; /* exception */
     epicsMutex ();
     ~epicsMutex ();
     void show ( unsigned level ) const;
@@ -39,6 +39,23 @@ private:
     epicsMutex & operator = ( const epicsMutex & );
 };
 
+class epicsShareClass epicsDeadlockDetectMutex {
+public:
+    typedef unsigned hierarchyLevel_t;
+    epicsDeadlockDetectMutex ( unsigned hierarchyLevel_t );
+    ~epicsDeadlockDetectMutex ();
+    void show ( unsigned level ) const;
+    void lock (); /* blocks until success */
+    void unlock ();
+    bool tryLock (); /* true if successful */
+private:
+    epicsMutex mutex;
+    const hierarchyLevel_t hierarchyLevel;
+    class epicsDeadlockDetectMutex * pPreviousLevel;
+    epicsDeadlockDetectMutex ( const epicsDeadlockDetectMutex & );
+    epicsDeadlockDetectMutex & operator = ( const epicsDeadlockDetectMutex & );
+};
+
 #endif /*__cplusplus*/
 
 #ifdef __cplusplus