core: add GetUnitByPIDFD method and use it in systemctl

A pid can be recycled, but a pidfd is pinned. Add a new method that is safer
as it takes a pidfd as input.
Return not only the D-Bus object path, but also the unit id and the last
recorded invocation id, as they are both useful (especially the id, as
converting from a path object to a unit id from a script requires another
round-trip via D-Bus).

Note that the manager still tracks processes by pid, so theorethically this
is not fully error-proof, but on the other hand the method response is
synchronous and the manager is single-threaded, so once a call is being
processed the unit database will not change anyway. Once the manager
switches to use pidfds everywhere, this can be further hardened.

This commit is contained in:

Luca Boccassi

2023-01-18 10:58:46 +01:00

committed by

Lennart Poettering

parent 9ca3bfb6c4

commit e0e7bc8223

5 changed files with 151 additions and 13 deletions

									
										test/units/testsuite-26.sh
									
		+1
		
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				@@ -245,6 +245,7 @@ systemctl status "systemd-*.timer"

				systemctl status "systemd-journald*.socket"

				systemctl status "sys-devices-*-ttyS0.device"

				systemctl status -- -.mount

				systemctl status 1

				# --marked

				systemctl restart "$UNIT_NAME"