vcl: avoid deadlock in X11 SelectionManager::shutdown()

It is evidently possible that SelectionManager::run() exits while
shutdown() is still trying to write to its end of the pipe, so close the
pipe when run() exits to avoid that.

(regression from ec5a7256ca549d358b9c5380194ea2d1b991a73e)

Change-Id: Ibc2823c61ea5df5b5227676c6e37ae5de44cde6b

1 files changed, 8 insertions, 4 deletions

diff --git a/vcl/unx/generic/dtrans/X11_selection.cxx b/vcl/unx/generic/dtrans/X11_selection.cxx
index 7a36159ebec2..2cdf21d81742 100644
--- a/vcl/unx/generic/dtrans/X11_selection.cxx
+++ b/vcl/unx/generic/dtrans/X11_selection.cxx
@@ -3782,6 +3782,10 @@ void SelectionManager::run( void* pThis )
             aLast = aNow;
         }
     }
+    // close write end on exit so write() fails and other thread does not block
+    // forever
+    close(This->m_EndThreadPipe[1]);
+    close(This->m_EndThreadPipe[0]);
 #if OSL_DEBUG_LEVEL > 1
     fprintf(stderr, "SelectionManager::run end\n" );
 #endif
@@ -3827,16 +3831,16 @@ void SelectionManager::shutdown() throw()
         aGuard.clear();
         while (osl_isThreadRunning(m_aThread))
         {
-            SolarMutexGuard guard2;
-            Application::Reschedule();
+            {   // drop mutex before write - otherwise may deadlock
+                SolarMutexGuard guard2;
+                Application::Reschedule();
+            }
             // trigger poll()'s wait end by writing a dummy value
             int dummy=0;
             dummy = write(m_EndThreadPipe[1], &dummy, 1);
         }
         osl_joinWithThread( m_aThread );
         osl_destroyThread( m_aThread );
-        close(m_EndThreadPipe[0]);
-        close(m_EndThreadPipe[1]);
         m_aThread = NULL;
         aGuard.reset();
     }