The bug re-occurred, after manually building libwayland with debugging symbols.
So I could do more debugging, and I think this Ubuntu bug needs to be reassigned to Xwayland. I have filed more details in the upstream Xwayland tracker. https://gitlab.freedesktop.org/xorg/xserver/-/issues/1648 ** Bug watch added: gitlab.freedesktop.org/xorg/xserver/-/issues #1648 https://gitlab.freedesktop.org/xorg/xserver/-/issues/1648 -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to mutter in Ubuntu. https://bugs.launchpad.net/bugs/2043517 Title: gnome-shell on non-active VT busy-loops through libwayland-server.so (sometimes) Status in mutter package in Ubuntu: New Bug description: I run several gnome sessions at once - different users on different Virtual Terminals. Sometimes, gnome-shell for a non-active VT starts using 100% CPU. Or, actually 99% CPU because it's doing IPC as well. And the corresponding XWayland uses 40% CPU. FWIW, sending SIGSTOP to either gnome-shell or XWayland stops the other one from busy-looping as well. If I switch back to the affected VT, it appears to function fine, but it is still using 100% + 40% CPU. Version numbers: Ubuntu 22.04.3 LTS gnome-shell 42.9-0ubuntu2 xwayland 2:22.1.1-1ubuntu0.7 $ ps -aux | grep 'alan .*gnome-shell$' alan 9248 26.1 3.4 5492888 269136 ? Rsl 19:54 30:26 /usr/bin/gnome-shell $ sudo strace -p 9248 2>&1|head strace: Process 9248 attached epoll_wait(37, [{events=EPOLLIN, data={u32=403234816, u64=139797293752320}}], 32, 0) = 1 recvmsg(21, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\1\0\0\0\0\0\f\0\3\0\0\0", iov_len=752}, {iov_base="", iov_len=3344}], msg_iovlen=2, msg_controllen=0, msg_flags=MSG_CMSG_CLOEXEC}, MSG_DONTWAIT|MSG_CMSG_CLOEXEC) = 12 write(4, "\1\0\0\0\0\0\0\0", 8) = 8 sendmsg(21, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\3\0\0\0\0\0\f\0[\2\0\0\1\0\0\0\1\0\f\0\3\0\0\0", iov_len=24}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, MSG_DONTWAIT|MSG_NOSIGNAL) = 24 poll([{fd=4, events=POLLIN}, {fd=8, events=POLLIN}, {fd=9, events=POLLIN}, {fd=19, events=POLLIN}, {fd=20, events=POLLIN}, {fd=23, events=POLLIN}, {fd=24, events=POLLIN}, {fd=25, events=POLLIN}, {fd=34, events=POLLIN}, {fd=36, events=POLLIN}, {fd=37, events=POLLIN}, {fd=54, events=POLLIN}, {fd=63, events=POLLIN}, {fd=66, events=POLLIN}], 14, 79809702) = 2 ([{fd=4, revents=POLLIN}, {fd=37, revents=POLLIN}]) read(4, "\2\0\0\0\0\0\0\0", 16) = 8 write(4, "\1\0\0\0\0\0\0\0", 8) = 8 epoll_wait(37, [{events=EPOLLIN, data={u32=403234816, u64=139797293752320}}], 32, 0) = 1 The recvmsg() call is here: #0 __libc_recvmsg (fd=21, msg=0x7fff1de64a50, flags=1073741888) at ../sysdeps/unix/sysv/linux/recvmsg.c:35 #1 0x00007f2531ea5ad6 in () at /lib/x86_64-linux-gnu/libwayland-server.so.0 #2 0x00007f2531ea4eea in wl_event_loop_dispatch () at /lib/x86_64-linux-gnu/libwayland-server.so.0 #3 0x00007f2531d2b45b in wayland_event_source_dispatch (base=<optimised out>, callback=<optimised out>, data=<optimised out>) at ../src/wayland/meta-wayland.c:110 #4 0x00007f2532b42d3b in g_main_dispatch (context=0x55c0046cc8f0) at ../../../glib/gmain.c:3419 #5 g_main_context_dispatch (context=0x55c0046cc8f0) at ../../../glib/gmain.c:4137 #6 0x00007f2532b98258 in g_main_context_iterate.constprop.0 (context=0x55c0046cc8f0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimised out>) at ../../../glib/gmain.c:4213 #7 0x00007f2532b422b3 in g_main_loop_run (loop=0x55c00698ae30) at ../../../glib/gmain.c:4413 #8 0x00007f2531cd0b79 in meta_context_run_main_loop (context=context@entry=0x55c0046c70c0, error=error@entry=0x7fff1de64f08) at ../src/core/meta-context.c:437 #9 0x000055c003cf4f12 in main (argc=<optimised out>, argv=<optimised out>) at ../src/main.c:650 The sendmsg() call is here: Thread 1 "gnome-shell" hit Breakpoint 1, __libc_sendmsg (fd=21, msg=0x7fff1de64c50, flags=16448) at ../sysdeps/unix/sysv/linux/sendmsg.c:26 26 ../sysdeps/unix/sysv/linux/sendmsg.c: No such file or directory. (gdb) where #0 __libc_sendmsg (fd=21, msg=0x7fff1de64c50, flags=16448) at ../sysdeps/unix/sysv/linux/sendmsg.c:26 #1 0x00007f2531ea1c9d in () at /lib/x86_64-linux-gnu/libwayland-server.so.0 #2 0x00007f2531ea565e in wl_display_flush_clients () at /lib/x86_64-linux-gnu/libwayland-server.so.0 #3 0x00007f2531d2b437 in wayland_event_source_prepare (base=base@entry=0x55c004a374d0, timeout=timeout@entry=0x7fff1de64dc4) at ../src/wayland/meta-wayland.c:97 #4 0x00007f2532b428e7 in g_main_context_prepare (context=0x55c0046cc8f0, priority=0x7fff1de64e50) at ../../../glib/gmain.c:3739 #5 0x00007f2532b98123 in g_main_context_iterate.constprop.0 (context=0x55c0046cc8f0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimised out>) at ../../../glib/gmain.c:4193 #6 0x00007f2532b422b3 in g_main_loop_run (loop=0x55c00698ae30) at ../../../glib/gmain.c:4413 #7 0x00007f2531cd0b79 in meta_context_run_main_loop (context=context@entry=0x55c0046c70c0, error=error@entry=0x7fff1de64f08) at ../src/core/meta-context.c:437 #8 0x000055c003cf4f12 in main (argc=<optimised out>, argv=<optimised out>) at ../src/main.c:650 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/2043517/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
