Split wxWakeUpPipe class in MT-unsafe and MT-safe parts.

This class can also be useful when it's used in the main thread only, so
leave the lock-less part of the code in wxWakeUpPipe and derive a separate
wxWakeUpPipeMT from it for the use in wxConsoleEventLoop where it can be used
by multiple threads.

See #10258.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74339 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/unix/evtloop.h

@@ -19,7 +19,7 @@
 
 class wxFDIODispatcher;
 class wxUnixEventLoopSource;
-class wxWakeUpPipe;
+class wxWakeUpPipeMT;
 
 class WXDLLIMPEXP_BASE wxConsoleEventLoop
 #ifdef __WXOSX__
@@ -52,7 +52,7 @@ protected:
 private:
     // pipe used for wake up messages: when a child thread wants to wake up
     // the event loop in the main thread it writes to this pipe
-    wxWakeUpPipe *m_wakeupPipe;
+    wxWakeUpPipeMT *m_wakeupPipe;
 
     // either wxSelectDispatcher or wxEpollDispatcher
     wxFDIODispatcher *m_dispatcher;

include/wx/unix/private/wakeuppipe.h

@@ -19,6 +19,9 @@
 // wxWakeUpPipe: allows to wake up the event loop by writing to it
 // ----------------------------------------------------------------------------
 
+// This class is not MT-safe, see wxWakeUpPipeMT below for a wake up pipe
+// usable from other threads.
+
 class wxWakeUpPipe : public wxFDIOHandler
 {
 public:
@@ -32,9 +35,11 @@ public:
     //
     // It simply writes to the write end of the pipe.
     //
-    // Notice that this method can be, and often is, called from another
+    // As indicated by its name, this method does no locking and so can be
-    // thread.
+    // called only from the main thread.
-    void WakeUp();
+    void WakeUpNoLock();
+
+    // Same as WakeUp() but without locking.
 
     // Return the read end of the pipe.
     int GetReadFd() { return m_pipe[wxPipe::Read]; }
@@ -48,9 +53,6 @@ public:
 private:
     wxPipe m_pipe;
 
-    // Protects access to m_pipeIsEmpty.
-    wxCriticalSection m_pipeLock;
-
     // This flag is set to true after writing to the pipe and reset to false
     // after reading from it in the main thread. Having it allows us to avoid
     // overflowing the pipe with too many writes if the main thread can't keep
@@ -58,4 +60,37 @@ private:
     bool m_pipeIsEmpty;
 };
 
+// ----------------------------------------------------------------------------
+// wxWakeUpPipeMT: thread-safe version of wxWakeUpPipe
+// ----------------------------------------------------------------------------
+
+// This class can be used from multiple threads, i.e. its WakeUp() can be
+// called concurrently.
+
+class wxWakeUpPipeMT : public wxWakeUpPipe
+{
+public:
+    wxWakeUpPipeMT() { }
+
+    // Thread-safe wrapper around WakeUpNoLock(): can be called from another
+    // thread to wake up the main one.
+    void WakeUp()
+    {
+        wxCriticalSectionLocker lock(m_pipeLock);
+
+        WakeUpNoLock();
+    }
+
+    virtual void OnReadWaiting()
+    {
+        wxCriticalSectionLocker lock(m_pipeLock);
+
+        wxWakeUpPipe::OnReadWaiting();
+    }
+
+private:
+    // Protects access to m_pipeIsEmpty.
+    wxCriticalSection m_pipeLock;
+};
+
 #endif // _WX_UNIX_PRIVATE_WAKEUPPIPE_H_

src/unix/evtloopunix.cpp

@@ -51,7 +51,7 @@
 
 wxConsoleEventLoop::wxConsoleEventLoop()
 {
-    m_wakeupPipe = new wxWakeUpPipe;
+    m_wakeupPipe = new wxWakeUpPipeMT;
     const int pipeFD = m_wakeupPipe->GetReadFd();
     if ( pipeFD == wxPipe::INVALID_FD )
     {

src/unix/wakeuppipe.cpp

@@ -69,10 +69,8 @@ wxWakeUpPipe::wxWakeUpPipe()
 // wakeup handling
 // ----------------------------------------------------------------------------
 
-void wxWakeUpPipe::WakeUp()
+void wxWakeUpPipe::WakeUpNoLock()
 {
-    wxCriticalSectionLocker lock(m_pipeLock);
-
     // No need to do anything if the pipe already contains something.
     if ( !m_pipeIsEmpty )
       return;
@@ -95,8 +93,6 @@ void wxWakeUpPipe::OnReadWaiting()
     // got wakeup from child thread, remove the data that provoked it from the
     // pipe
 
-    wxCriticalSectionLocker lock(m_pipeLock);
-
     char buf[4];
     for ( ;; )
     {