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Diffstat (limited to 'results/classifier/001/instruction/11357571')
| -rw-r--r-- | results/classifier/001/instruction/11357571 | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/results/classifier/001/instruction/11357571 b/results/classifier/001/instruction/11357571 new file mode 100644 index 00000000..1c3bc483 --- /dev/null +++ b/results/classifier/001/instruction/11357571 @@ -0,0 +1,47 @@ +instruction: 0.758 +semantic: 0.694 +other: 0.687 +mistranslation: 0.516 + +[Qemu-devel] [BUG] VNC: client won't send FramebufferUpdateRequest if job in flight is aborted + +Hi Gerd, Daniel. + +We noticed that if VncSharePolicy was configured with +VNC_SHARE_POLICY_FORCE_SHARED mode and +multiple vnc clients opened vnc connections, some clients could go blank screen +at high probability. +This problem can be reproduced when we regularly reboot suse12sp3 in graphic +mode both +with RealVNC and noVNC client. + +Then we dig into it and find out that some clients go blank screen because they +don't +send FramebufferUpdateRequest any more. One step further, we notice that each +time +the job in flight is aborted one client go blank screen. + +The bug is triggered in the following procedure. +Guest reboot => graphic mode switch => graphic_hw_update => vga_update_display +=> vga_draw_graphic (full_update = 1) => dpy_gfx_replace_surface => +vnc_dpy_switch => +vnc_abort_display_jobs (client may have job in flight) => job removed from the +queue +If one client has vnc job in flight, *vnc_abort_display_jobs* will wait until +its job is abandoned. +This behavior is done in vnc_worker_thread_loop when 'if (job->vs->ioc == NULL +|| job->vs->abort == true)' +branch is taken. + +As we can see, *vnc_abort_display_jobs* is intended to do some optimization to +avoid unnecessary client update. +But if client sends FramebufferUpdateRequest for some graphic area and its +FramebufferUpdate response job +is abandoned, the client may wait for the response and never send new +FramebufferUpdateRequest, which may +case the client go blank screen forever. + +So I am wondering whether we should drop the *vnc_abort_display_jobs* +optimization or do some trick here +to push the client to send new FramebufferUpdateRequest. Do you have any idea ? + |