When running udevadm settle --timeout=0, the ping always times out, and
udevadm will return 0 without checking the queue state.
(David: Use a reasonable timeout to still get the barrier provided by
ctrl-ping)
udevadm manual says:
A value of 0 will check if the queue is empty and always return
immediately.
However, currently we ignore the deadline if the value is 0, and wait
without any limit.
Zero timeout behaved according to the documentation until commit
ead7c62ab7 (udevadm: settle - kill alarm()). Looking at this patch, it
seems that the behavior change was unintended.
This patch restores the documented behavior.
Commit 9ea28c55a2 (udev: remove seqnum API and all assumptions about
seqnums) introduced a regresion, ignoring the timeout option when
waiting until the event queue is empty.
Previously, if the udev event queue was not empty when the timeout was
expired, udevadm settle was returning with exit code 1. To check if the
queue is empty, you could invoke udevadm settle with timeout=0. This
patch restores the previous behavior.
(David: fixed timeout==0 handling and dropped redundant assignment)
Nir Soffer