| Message ID | 20220105020808.597325-1-lei.rao@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] ui/vnc.c: Fixed a deadlock bug. | expand |
diff --git a/ui/vnc.c b/ui/vnc.c index 1ed1c7efc6..3ccd33dedc 100644 --- a/ui/vnc.c +++ b/ui/vnc.c @@ -1354,12 +1354,12 @@ void vnc_disconnect_finish(VncState *vs) /* last client gone */ vnc_update_server_surface(vs->vd); } + vnc_unlock_output(vs); + if (vs->cbpeer.notifier.notify) { qemu_clipboard_peer_unregister(&vs->cbpeer); } - vnc_unlock_output(vs); - qemu_mutex_destroy(&vs->output_mutex); if (vs->bh != NULL) { qemu_bh_delete(vs->bh);
The GDB statck is as follows: (gdb) bt 0 __lll_lock_wait (futex=futex@entry=0x56211df20360, private=0) at lowlevellock.c:52 1 0x00007f263caf20a3 in __GI___pthread_mutex_lock (mutex=0x56211df20360) at ../nptl/pthread_mutex_lock.c:80 2 0x000056211a757364 in qemu_mutex_lock_impl (mutex=0x56211df20360, file=0x56211a804857 "../ui/vnc-jobs.h", line=60) at ../util/qemu-thread-posix.c:80 3 0x000056211a0ef8c7 in vnc_lock_output (vs=0x56211df14200) at ../ui/vnc-jobs.h:60 4 0x000056211a0efcb7 in vnc_clipboard_send (vs=0x56211df14200, count=1, dwords=0x7ffdf1701338) at ../ui/vnc-clipboard.c:138 5 0x000056211a0f0129 in vnc_clipboard_notify (notifier=0x56211df244c8, data=0x56211dd1bbf0) at ../ui/vnc-clipboard.c:209 6 0x000056211a75dde8 in notifier_list_notify (list=0x56211afa17d0 <clipboard_notifiers>, data=0x56211dd1bbf0) at ../util/notify.c:39 7 0x000056211a0bf0e6 in qemu_clipboard_update (info=0x56211dd1bbf0) at ../ui/clipboard.c:50 8 0x000056211a0bf05d in qemu_clipboard_peer_release (peer=0x56211df244c0, selection=QEMU_CLIPBOARD_SELECTION_CLIPBOARD) at ../ui/clipboard.c:41 9 0x000056211a0bef9b in qemu_clipboard_peer_unregister (peer=0x56211df244c0) at ../ui/clipboard.c:19 10 0x000056211a0d45f3 in vnc_disconnect_finish (vs=0x56211df14200) at ../ui/vnc.c:1358 11 0x000056211a0d4c9d in vnc_client_read (vs=0x56211df14200) at ../ui/vnc.c:1611 12 0x000056211a0d4df8 in vnc_client_io (ioc=0x56211ce70690, condition=G_IO_IN, opaque=0x56211df14200) at ../ui/vnc.c:1649 13 0x000056211a5b976c in qio_channel_fd_source_dispatch (source=0x56211ce50a00, callback=0x56211a0d4d71 <vnc_client_io>, user_data=0x56211df14200) at ../io/channel-watch.c:84 14 0x00007f263ccede8e in g_main_context_dispatch () at /lib/x86_64-linux-gnu/libglib-2.0.so.0 15 0x000056211a77d4a1 in glib_pollfds_poll () at ../util/main-loop.c:232 16 0x000056211a77d51f in os_host_main_loop_wait (timeout=958545) at ../util/main-loop.c:255 17 0x000056211a77d630 in main_loop_wait (nonblocking=0) at ../util/main-loop.c:531 18 0x000056211a45bc8e in qemu_main_loop () at ../softmmu/runstate.c:726 19 0x000056211a0b45fa in main (argc=69, argv=0x7ffdf1701778, envp=0x7ffdf17019a8) at ../softmmu/main.c:50 From the call trace, we can see it is a deadlock bug. vnc_disconnect_finish will acquire the output_mutex. But, the output_mutex will be acquired again in vnc_clipboard_send. Repeated locking will cause deadlock. So, I move qemu_clipboard_peer_unregister() behind vnc_unlock_output(); Fixes: 0bf41cab93e ("ui/vnc: clipboard support") Signed-off-by: Lei Rao <lei.rao@intel.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> --- ui/vnc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)