Fix a race condition where we might get updates thrown at us right after a
framebuffer switch, but before we've been given the pointer to the new
framebuffer.
git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4839 3789f03b-4d11-0410-bbf8-ca57d06f2519
diff --git a/common/rfb/VNCServer.h b/common/rfb/VNCServer.h
index 4e55479..280b68b 100644
--- a/common/rfb/VNCServer.h
+++ b/common/rfb/VNCServer.h
@@ -30,6 +30,13 @@
class VNCServer : public UpdateTracker {
public:
+ // blockUpdates()/unblockUpdates() tells the server that the pixel buffer
+ // is currently in flux and may not be accessed. The attributes of the
+ // pixel buffer may still be accessed, but not the frame buffer itself.
+ // Note that access must be unblocked the exact same number of times it
+ // was blocked.
+ virtual void blockUpdates() = 0;
+ virtual void unblockUpdates() = 0;
// setPixelBuffer() tells the server to use the given pixel buffer (and
// optionally a modified screen layout). If this differs in size from
diff --git a/common/rfb/VNCServerST.cxx b/common/rfb/VNCServerST.cxx
index 697695d..b07f5c3 100644
--- a/common/rfb/VNCServerST.cxx
+++ b/common/rfb/VNCServerST.cxx
@@ -47,6 +47,7 @@
// otherwise blacklisted connections might be "forgotten".
+#include <assert.h>
#include <stdlib.h>
#include <rfb/ServerCore.h>
@@ -77,7 +78,8 @@
// -=- Constructors/Destructor
VNCServerST::VNCServerST(const char* name_, SDesktop* desktop_)
- : blHosts(&blacklist), desktop(desktop_), desktopStarted(false), pb(0),
+ : blHosts(&blacklist), desktop(desktop_), desktopStarted(false),
+ blockCounter(0), pb(0),
name(strDup(name_)), pointerClient(0), comparer(0),
renderedCursorInvalid(false),
queryConnectionHandler(0), keyRemapper(&KeyRemapper::defInstance),
@@ -259,6 +261,22 @@
// VNCServer methods
+void VNCServerST::blockUpdates()
+{
+ blockCounter++;
+}
+
+void VNCServerST::unblockUpdates()
+{
+ assert(blockCounter > 0);
+
+ blockCounter--;
+
+ // Flush out any updates we might have blocked
+ if (blockCounter == 0)
+ tryUpdate();
+}
+
void VNCServerST::setPixelBuffer(PixelBuffer* pb_, const ScreenSet& layout)
{
pb = pb_;
@@ -545,6 +563,9 @@
{
std::list<VNCSConnectionST*>::iterator ci, ci_next;
+ if (blockCounter > 0)
+ return;
+
if (!checkDefer())
return;
@@ -571,6 +592,10 @@
if (ui.is_empty() && !(renderCursor && renderedCursorInvalid))
return true;
+ // Block clients as the frame buffer cannot be safely accessed
+ if (blockCounter > 0)
+ return false;
+
// Block client from updating if we are currently deferring updates
if (!checkDefer())
return false;
diff --git a/common/rfb/VNCServerST.h b/common/rfb/VNCServerST.h
index 2fed0a8..e75954f 100644
--- a/common/rfb/VNCServerST.h
+++ b/common/rfb/VNCServerST.h
@@ -82,6 +82,8 @@
// Methods overridden from VNCServer
+ virtual void blockUpdates();
+ virtual void unblockUpdates();
virtual void setPixelBuffer(PixelBuffer* pb, const ScreenSet& layout);
virtual void setPixelBuffer(PixelBuffer* pb);
virtual void setScreenLayout(const ScreenSet& layout);
@@ -209,6 +211,7 @@
SDesktop* desktop;
bool desktopStarted;
+ int blockCounter;
PixelBuffer* pb;
ScreenSet screenLayout;