[Qemu-devel] [PATCH] vnc: threaded server depends on io-thread

[Corentin Chary <corentin.chary@gmail.com>]

The threaded VNC servers messed up with QEMU fd handlers without
any kind of locking, and that can cause some nasty race conditions.

The IO-Thread provides appropriate locking primitives to avoid that.
This patch makes CONFIG_VNC_THREAD depends on CONFIG_IO_THREAD,
and add lock and unlock calls around the two faulty calls.

Thanks to Jan Kiszka for helping me solve this issue.

Cc: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: Corentin Chary <corentin.chary@gmail.com>
---
 configure           |    9 +++++++++
 ui/vnc-jobs-async.c |    4 ++++
 2 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/configure b/configure
index 5513d3e..c8c1ac1 100755
--- a/configure
+++ b/configure
@@ -2455,6 +2455,15 @@ if test \( "$cpu" = "i386" -o "$cpu" = "x86_64" \) -a \
   roms="optionrom"
 fi
 
+# VNC Thread depends on IO Thread
+if test "$vnc_thread" = "yes" -a "$io_thread" != "yes"; then
+  echo
+  echo "ERROR: VNC thread depends on IO thread which isn't enabled."
+  echo "Please use --enable-io-thread if you want to enable it."
+  echo
+  exit 1
+fi
+
 
 echo "Install prefix    $prefix"
 echo "BIOS directory    `eval echo $datadir`"
diff --git a/ui/vnc-jobs-async.c b/ui/vnc-jobs-async.c
index f596247..093c0d4 100644
--- a/ui/vnc-jobs-async.c
+++ b/ui/vnc-jobs-async.c
@@ -260,7 +260,9 @@ static int vnc_worker_thread_loop(VncJobQueue *queue)
         goto disconnected;
     }
 
+    qemu_mutex_lock_iothread();
     vnc_write(job->vs, vs.output.buffer, vs.output.offset);
+    qemu_mutex_unlock_iothread();
 
 disconnected:
     /* Copy persistent encoding data */
@@ -269,7 +271,9 @@ disconnected:
     vnc_unlock_output(job->vs);
 
     if (flush) {
+        qemu_mutex_lock_iothread();
         vnc_flush(job->vs);
+        qemu_mutex_unlock_iothread();
     }
 
     vnc_lock_queue(queue);
-- 
1.7.3.4