[win-pv-devel] [PATCH 14/20] Protect active device with critical section

[Owen Smith <owen.smith@xxxxxxxxxx>]

This should prevent race conditions due to device removal while
currently attempting operations. Will ensure the m_dev pointer
is not removed during a OnSuspend or OnShutdown operation

Signed-off-by: Owen Smith <owen.smith@xxxxxxxxxx>
---
 src/liteagent/LiteAgent.cpp | 32 +++++++++++++++++++++++++++++++-
 src/liteagent/LiteAgent.h   |  1 +
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/src/liteagent/LiteAgent.cpp b/src/liteagent/LiteAgent.cpp
index b61967f..db6c3b9 100644
--- a/src/liteagent/LiteAgent.cpp
+++ b/src/liteagent/LiteAgent.cpp
@@ -42,6 +42,24 @@
 #define XENTOOLS_INSTALL_REG_KEY64 "SOFTWARE\\Wow6432Node\\Citrix\\XenTools"
 #endif
 
+class CCritSec
+{
+public:
+    CCritSec(LPCRITICAL_SECTION crit);
+    ~CCritSec();
+private:
+    LPCRITICAL_SECTION m_crit;
+};
+
+CCritSec::CCritSec(LPCRITICAL_SECTION crit) : m_crit(crit)
+{
+    EnterCriticalSection(m_crit);
+}
+CCritSec::~CCritSec()
+{
+    LeaveCriticalSection(m_crit);
+}
+
 int __stdcall WinMain(HINSTANCE hInstance, HINSTANCE ignore, LPSTR lpCmdLine, 
int nCmdShow)
 {
     if (strlen(lpCmdLine) != 0) {
@@ -169,7 +187,9 @@ CLiteAgent::CLiteAgent() :
 
     m_svc_stop = CreateEvent(FALSE, NULL, NULL, FALSE);
     m_shutdown = CreateEvent(FALSE, NULL, NULL, FALSE);
-    m_suspend  = CreateEvent(FALSE, NULL, NULL, FALSE); 
+    m_suspend  = CreateEvent(FALSE, NULL, NULL, FALSE);
+
+    InitializeCriticalSection(&m_crit);
 }
 
 CLiteAgent::~CLiteAgent()
@@ -177,6 +197,8 @@ CLiteAgent::~CLiteAgent()
     CloseHandle(m_svc_stop);
     CloseHandle(m_shutdown);
     CloseHandle(m_suspend);
+
+    DeleteCriticalSection(&m_crit);
 }
 
 /*virtual*/ CDevice* CLiteAgent::Create(const wchar_t* path)
@@ -188,6 +210,8 @@ CLiteAgent::~CLiteAgent()
 /*virtual*/ void CLiteAgent::OnDeviceAdded(CDevice* dev)
 {
     CLiteAgent::Log("OnDeviceAdded(%ws)\n", dev->Path());
+
+    CCritSec crit(&m_crit);
     if (m_dev == NULL) {
         m_dev = (CXenIfaceItf*)dev;
         // setting active device
@@ -210,6 +234,8 @@ CLiteAgent::~CLiteAgent()
 /*virtual*/ void CLiteAgent::OnDeviceRemoved(CDevice* dev)
 {
     CLiteAgent::Log("OnDeviceRemoved(%ws)\n", dev->Path());
+
+    CCritSec crit(&m_crit);
     if ((CXenIfaceItf*)dev == m_dev) {
         // active device removed
         CLiteAgent::Log("Active Device Removed\n");
@@ -273,6 +299,8 @@ bool CLiteAgent::ServiceMainLoop()
 
 void CLiteAgent::OnShutdown()
 {
+    CCritSec crit(&m_crit);
+
     if (m_dev == NULL)
         return;
     CLiteAgent::Log("OnShutdown(%ws)\n", m_dev->Path());
@@ -286,6 +314,8 @@ void CLiteAgent::OnShutdown()
 
 void CLiteAgent::OnSuspend()
 {
+    CCritSec crit(&m_crit);
+
     if (m_dev == NULL)
         return;
     CLiteAgent::Log("OnSuspend(%ws)\n", m_dev->Path());
diff --git a/src/liteagent/LiteAgent.h b/src/liteagent/LiteAgent.h
index 97c6514..e3a2573 100644
--- a/src/liteagent/LiteAgent.h
+++ b/src/liteagent/LiteAgent.h
@@ -87,6 +87,7 @@ private: // service support
     HANDLE                  m_shutdown;
     HANDLE                  m_suspend;
 
+    CRITICAL_SECTION        m_crit;
     CDeviceList             m_devs;
     CXenIfaceItf*           m_dev;
     void*                   m_ctxt_shutdown;
-- 
1.9.4.msysgit.1


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