udev-monitor: make the monitor fd non-blocking#19
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systemd's libudev documents that the monitor socket is non-blocking by default: https://github.com/systemd/systemd/blob/v261/src/libudev/libudev-monitor.c#L228-L231 It also creates the monitor socket with SOCK_NONBLOCK: https://github.com/systemd/systemd/blob/v261/src/libsystemd/sd-device/device-monitor.c#L179-L183 libudev-devd currently uses a blocking pipe. Once all pending events have been consumed, another call to udev_monitor_receive_device() blocks instead of returning NULL with EAGAIN. This was observed in KWin, where display hotplug handling stalled after disconnecting and reconnecting an external display in a KDE/Wayland session. Set O_NONBLOCK on the read end returned by udev_monitor_get_fd(). Keep the internal write end blocking to preserve the current producer and backpressure behavior. Sponsored by: The FreeBSD Foundation
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systemd's libudev documents that the monitor socket is non-blocking by default:
https://github.com/systemd/systemd/blob/v261/src/libudev/libudev-monitor.c#L228-L231
It also creates the monitor socket with SOCK_NONBLOCK:
https://github.com/systemd/systemd/blob/v261/src/libsystemd/sd-device/device-monitor.c#L179-L183
libudev-devd currently uses a blocking pipe. Once all pending events have been consumed, another call to udev_monitor_receive_device() blocks instead of returning NULL with EAGAIN.
This was observed in KWin, where display hotplug handling stalled after disconnecting and reconnecting an external display in a KDE/Wayland session.
Set O_NONBLOCK on the read end returned by udev_monitor_get_fd(). Keep the internal write end blocking to preserve the current producer and backpressure behavior.
Sponsored by: The FreeBSD Foundation