This function is only used for logind, which is Linux-specific, but the
presence in common/drm.c suggested that it had to be portable.
Move it to the logind backend for now.
When device open or close messages are sent to seatd, libseat must read
messages from the socket until it sees the associated response message.
This means that it may drain enable/disable seat events from the socket,
queueing them internally for deferred processing.
As the socket is drained, the caller will not wake from a poll and have
no reason to dispatch libseat. To ensure that these messages would not
be left in the queue, 6fa82930d0 made it
so that open/close calls would execute all queued events just before
returning.
Unfortunately, this had the side-effect of having events fire from the
stack of libseat_open_device or libseat_close_device, which we now see
cause problems in compositors. Specifically, an issue has been observed
where libinput end up calling libseat_close_device, which in turn
dispatch a disable seat event that calls libinput_suspend. libinput does
not like this.
Instead, remove the execution from libseat_open_device and
libseat_close_device, and instead make a "ping" request to seatd if
events have been queued. The response to this will wake us up and ensure
that dispatch is called.
The kernel Secure Attention Key killer, triggered by SysRq+k, kills all
processes that hold an fd referencing the tty.
To avoid its attention, we stop storing the fd for the currently active
VT in seat state. This has the added benefit of simplifying state a bit.
This is useful for headless testing, for instance with VKMS:
modprobe vkms
export WLR_DRM_DEVICES=/dev/dri/card1
export WLR_BACKENDS=drm
export LIBSEAT_BACKEND=noop
sway
We don't need any of the VT handling in this case.
If a client closed while it was disabled, the VT would not be torn down.
If the user navigated back to the VT it belonged to, they would be
stuck.
When a client is disabled, open the fd for the VT it belonged to and
perform regular teardown on it.
Linux only requires acking release and ignores ack of acquire, but
FreeBSD is more stringent and will patiently wait for both to be acked.
Implement proper acking for both events.
The seat activation logic did not correctly handle VT switching and
switching between multiple sessions.
Session switching on VT-bound seats is now performed using a VT switch,
taking advantage of VT signals to perform the actual switch. This
simplifies switching logic and makes it more robust.
Signal handling relied on poll(2) being interrupted by signals, followed
by a check for signal handlers flagging a signal as received. This only
allowed signals that were received during poll(2) to be handled
correctly.
Implement the usual self-pipe implementation, where signal handlers
write an arbitrary byte to a polled file descriptor to ensure proper
level-triggered signal handling.
test_run and test_assert replaces regular assert with better logging
which include the currently running test name. The tests can now also be
built without DEBUG.
Add helpers around connection access to have all logging centralized and
reduce code duplication. Improve existing helpers to further reduce code
duplication.
The seatd backend should have much better logging after this.
Previously, seatd would not deactivate devices until the client had
acked the disable. In once instance, this lead to libinput spending
significant time checking and closing each input device.
As a workaround, mimick logind's behavior of deactivating devices first.
The original behavior can be reintroduced if the client-side problem is
fixed.
Closes: https://todo.sr.ht/~kennylevinsen/seatd/5
