Tried the same python minimal application with pyqt5 (qt 5.9.5) - and no, it does not happen.
So it seems to be a QT4 problem somehow in connection to the gnome- panel, because this does not happen with the same QT4 application and fbpanel in the same environment. stracing the gnome-panel with this pyqt5 app, a similar output is logged, but not as frequent as with qt4: restart_syscall(<... resuming interrupted poll ...>) = 1 recvmsg(3, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\34\0\260\202\275\2\0\0\21\2\0\0:\201\247\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", iov_len=4096}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 32 recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) poll([{fd=3, events=POLLIN}, {fd=4, events=POLLIN}, {fd=6, events=POLLIN}], 3, -1) = 1 ([{fd=3, revents=POLLIN}]) recvmsg(3, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\34\0\260\202\275\2\0\0\21\2\0\0R\324\247\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", iov_len=4096}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 32 recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) recvmsg(3, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable) poll([{fd=3, events=POLLIN}, {fd=4, events=POLLIN}, {fd=6, events=POLLIN}], 3, -1 I attached the pyqt5 tray app if somebody wants to take a look at that. But the CPU load disappears with QT5. ** Attachment added: "python-tray-qt5.tar.gz" https://bugs.launchpad.net/ubuntu/+source/gnome-panel/+bug/1779663/+attachment/5159066/+files/python-tray-qt5.tar.gz -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1779663 Title: QT4 Tray application and CPU load in 18.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-panel/+bug/1779663/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs