From 5177298dad0efafbf17c695ba8afecb944d474ab Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Tue, 4 Nov 2014 20:06:05 +0000
Subject: [PATCH] Change isRunning variable to an Atomic to address possible
 race condition asscoiated with reading and writing to the variable from
 different threads.

git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@14464 16af8721-9629-0410-8352-f15c8da7e697
---
 src/OpenThreads/pthreads/PThread.cpp          | 20 +++++++++----------
 src/OpenThreads/pthreads/PThreadPrivateData.h | 20 +++++++++++--------
 2 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/src/OpenThreads/pthreads/PThread.cpp b/src/OpenThreads/pthreads/PThread.cpp
index f01bc1675..66e97c96a 100644
--- a/src/OpenThreads/pthreads/PThread.cpp
+++ b/src/OpenThreads/pthreads/PThread.cpp
@@ -83,7 +83,7 @@ struct ThreadCleanupStruct
 {
 
     OpenThreads::Thread *thread;
-    volatile bool *runflag;
+    Atomic *runflag;
 
 };
 
@@ -97,7 +97,7 @@ void thread_cleanup_handler(void *arg)
     ThreadCleanupStruct *tcs = static_cast<ThreadCleanupStruct *>(arg);
 
     tcs->thread->cancelCleanup();
-    *(tcs->runflag) = false;
+    (*(tcs->runflag)).exchange(0);
 
 }
 
@@ -176,7 +176,7 @@ private:
 
         ThreadCleanupStruct tcs;
         tcs.thread = thread;
-        tcs.runflag = &pd->isRunning;
+        tcs.runflag = &pd->_isRunning;
 
         // Set local storage so that Thread::CurrentThread() can return the right thing
         int status = pthread_setspecific(PThreadPrivateData::s_tls_key, thread);
@@ -196,14 +196,14 @@ private:
 
 #endif // ] ALLOW_PRIORITY_SCHEDULING
 
-        pd->isRunning = true;
+        pd->setRunning(true);
 
         // release the thread that created this thread.
         pd->threadStartedBlock.release();
 
         thread->run();
 
-        pd->isRunning = false;
+        pd->setRunning(false);
 
         pthread_cleanup_pop(0);
 
@@ -426,7 +426,7 @@ Thread::Thread()
     pd->stackSize = 0;
     pd->stackSizeLocked = false;
     pd->idSet = false;
-    pd->isRunning = false;
+    pd->setRunning(false);
     pd->isCanceled = false;
     pd->uniqueId = pd->nextId;
     pd->nextId++;
@@ -448,7 +448,7 @@ Thread::~Thread()
 {
     PThreadPrivateData *pd = static_cast<PThreadPrivateData *>(_prvData);
 
-    if(pd->isRunning)
+    if(pd->isRunning())
     {
         std::cout<<"Error: Thread "<<this<<" still running in destructor"<<std::endl;
 
@@ -594,7 +594,7 @@ int Thread::setProcessorAffinity(unsigned int cpunum)
 
 #elif defined(HAVE_PTHREAD_SETAFFINITY_NP) || defined(HAVE_THREE_PARAM_SCHED_SETAFFINITY) || defined(HAVE_TWO_PARAM_SCHED_SETAFFINITY)
 
-    if (pd->isRunning && Thread::CurrentThread()==this)
+    if (pd->isRunning() && Thread::CurrentThread()==this)
     {
         cpu_set_t cpumask;
         CPU_ZERO( &cpumask );
@@ -624,7 +624,7 @@ int Thread::setProcessorAffinity(unsigned int cpunum)
 bool Thread::isRunning()
 {
     PThreadPrivateData *pd = static_cast<PThreadPrivateData *> (_prvData);
-    return pd->isRunning;
+    return pd->isRunning();
 
 }
 
@@ -783,7 +783,7 @@ int Thread::cancel()
 {
 #if defined(HAVE_PTHREAD_CANCEL)
     PThreadPrivateData *pd = static_cast<PThreadPrivateData *> (_prvData);
-    if (pd->isRunning)
+    if (pd->isRunning())
     {
         pd->isCanceled = true;
         int status = pthread_cancel(pd->tid);
diff --git a/src/OpenThreads/pthreads/PThreadPrivateData.h b/src/OpenThreads/pthreads/PThreadPrivateData.h
index a8297fd2b..0864affcb 100644
--- a/src/OpenThreads/pthreads/PThreadPrivateData.h
+++ b/src/OpenThreads/pthreads/PThreadPrivateData.h
@@ -1,13 +1,13 @@
 /* -*-c++-*- OpenThreads library, Copyright (C) 2002 - 2007  The Open Thread Group
  *
- * This library is open source and may be redistributed and/or modified under  
- * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
+ * This library is open source and may be redistributed and/or modified under
+ * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
  * (at your option) any later version.  The full license is in LICENSE file
  * included with this distribution, and on the openscenegraph.org website.
- * 
+ *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * OpenSceneGraph Public License for more details.
 */
 
@@ -22,6 +22,7 @@
 #include <pthread.h>
 #include <OpenThreads/Thread>
 #include <OpenThreads/Block>
+#include <OpenThreads/Atomic>
 
 namespace OpenThreads {
 
@@ -33,7 +34,7 @@ class PThreadPrivateData {
     friend class Thread;
 
     //-------------------------------------------------------------------------
-    // We're friendly to PThreadPrivateActions, so it can get at some 
+    // We're friendly to PThreadPrivateActions, so it can get at some
     // variables.
     //
     friend class ThreadPrivateActions;
@@ -48,7 +49,10 @@ private:
 
     volatile bool stackSizeLocked;
 
-    volatile bool isRunning;
+    void setRunning(bool flag) { _isRunning.exchange(flag); }
+    bool isRunning() const { return _isRunning!=0; }
+
+    Atomic _isRunning;
 
     Block threadStartedBlock;
 
@@ -57,7 +61,7 @@ private:
     volatile bool idSet;
 
     volatile Thread::ThreadPriority threadPriority;
-    
+
     volatile Thread::ThreadPolicy threadPolicy;
 
     pthread_t tid;
@@ -65,7 +69,7 @@ private:
     volatile int uniqueId;
 
     volatile int cpunum;
-    
+
 
     static int nextId;