[Spice-devel] [PATCH spice] Fix dcc_start() regression

[Marc-André Lureau]

Commit e9ed125d introduced a dead-lock regression by taking twice the
same lock recursively. The previous code checked if a dmabuf was set
without taking the lock, for queuing scanout messages. Since the message
is being processed later on, it make sense to queue and delay until it
is sent to check if there is a scanout.

backtrace:
 #0  red_qxl_get_gl_scanout (qxl_state=0x5555582373c0) at red-qxl.c:828
 #1  0x00007fffec1ae654 in marshall_gl_scanout (rcc=0x7fffda6a7010,
 #m=0x7fff44025e60, item=0x7fff440958a0) at dcc-send.c:2310
 #2  0x00007fffec1aec7b in dcc_send_item (dcc=0x7fffda6a7010,
 #pipe_item=0x7fff440958a0) at dcc-send.c:2441
 #3  0x00007fffec1730f6 in send_item (rcc=0x7fffda6a7010,
 #item=0x7fff440958a0) at display-channel.c:1963
 #4  0x00007fffec1504c3 in
 #red_channel_client_send_item (rcc=0x7fffda6a7010, item=0x7fff440958a0)
 #at red-channel.c:578
 #5  0x00007fffec152d98 in red_channel_client_push (rcc=0x7fffda6a7010)
 #at red-channel.c:1365
 #6  0x00007fffec1a387e in dcc_push_monitors_config (dcc=0x7fffda6a7010)
 #at dcc.c:563
 #7  0x00007fffec1a3489 in dcc_start (dcc=0x7fffda6a7010) at dcc.c:475

Signed-off-by: Marc-André Lureau <marcandre.lureau at redhat.com>
---
 server/dcc.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/server/dcc.c b/server/dcc.c
index 70a9b99..1f71423 100644
--- a/server/dcc.c
+++ b/server/dcc.c
@@ -446,7 +446,6 @@ void dcc_start(DisplayChannelClient *dcc)
 {
     DisplayChannel *display = DCC_TO_DC(dcc);
     RedChannelClient *rcc = RED_CHANNEL_CLIENT(dcc);
-    QXLInstance *qxl = display->common.qxl;
 
     red_channel_client_push_set_ack(RED_CHANNEL_CLIENT(dcc));
 
@@ -467,17 +466,11 @@ void dcc_start(DisplayChannelClient *dcc)
         dcc_create_all_streams(dcc);
     }
 
-    SpiceMsgDisplayGlScanoutUnix *scanout = red_qxl_get_gl_scanout(qxl->st);
-    if (scanout) {
-        if (reds_stream_is_plain_unix(rcc->stream) &&
-            red_channel_client_test_remote_cap(rcc, SPICE_DISPLAY_CAP_GL_SCANOUT)) {
-            red_channel_client_pipe_add(rcc, dcc_gl_scanout_item_new(rcc, NULL, 0));
-            dcc_push_monitors_config(dcc);
-        } else {
-            spice_printerr("FIXME: GL not supported on this kind of connection");
-        }
+    if (reds_stream_is_plain_unix(rcc->stream) &&
+        red_channel_client_test_remote_cap(rcc, SPICE_DISPLAY_CAP_GL_SCANOUT)) {
+        red_channel_client_pipe_add(rcc, dcc_gl_scanout_item_new(rcc, NULL, 0));
+        dcc_push_monitors_config(dcc);
     }
-    red_qxl_put_gl_scanout(qxl->st, scanout);
 }
 
 static void dcc_destroy_stream_agents(DisplayChannelClient *dcc)
-- 
2.5.0