Let's show the runtimes of our commands and preparations for them. It's
actually quite interesting, we sometimes are irritatingly slow with our
handoffs.
Also: rename Handover → Handoff. I think it makes it clearer that this
is not really about handing over any resources, but that the executor is
out off the game from that point on.
This changes the executor to systematically send handoff timestamps to
the service manager if a socket for that is supplied. This drops the
code that did this via Type=exec messages, and reverts that part to the
old behaviour before 93cb78aee2.
Benefits of this approach:
1. We can collect the handoff for any command we fork off, regardless
if it's ExecStart= something else, regardless whether it's Type=exec,
Type=simple or some any other service type, regardless of the unit
type.
2. We collect both CLOCK_REALTIME and CLOCK_MONOTONIC, as we do for the
other process timestamps.
3. It's entirely backwards compatible, as this doesn't change the
protocol between service manager and executor, but just extends it.
This adds an AF_UNIX socket pair to the manager that we can collect
handoff timestamp messages on.
The idea is that forked off children send a datagram with a timestamp
and we use its sender PID to match it against the right forked off
process.
This part only implements the receiving side: a socket is created, and
listened on. Received datagrams are parsed, verified and then dispatched
to the interested units.
assert_se() should not be used here, these checks are paranoia only and
have no side-effect after all.
hence fix this to use assert(), or in fact ASSERT_PTR()
The prototype was static, but the implementation was not. Make both
static, this is otherwise too confusing. (This doesn't actually change
anything, since the prototype decides about this anyway, but it makes
things easier to read.)
While stracing PID1's forking off of children I noticed that every
single forked off child reads cap_last_cap from procfs. That value is a
kernel constant, hence we can save a lot of work if we'd cache it.
Thing is, we actually do cache it, in a thread_local cache field. This
means that the forked off processes (which are considered new threads)
will have to re-query it, even though we already know the result.
Hence, let's get rid of the thread_local stuff (given that the value is
going to be the same for all threads anyway, and we pretty much have a
single thread only anyway). Use an C11 atomic_int instead, which ensures
the value is either initialized or not initialized, but we don't need to
be concerned of partial initialization.
This makes the cap_last_cap reading go away in the children, as strace
shows (since cap_last_cap() is already called by PID 1 before
fork()ing, anyway).
If an assert in systemd fails it can't shut down normally.
By default it freezes. For interactive runs we want the crash shell
to enable further debugging, but during test runs we want it to exit
without having to wait for the test timeout.
By deactivating the crash shell, enabling reboot, and configuring qemu
so that it shuts down instead of rebooting we can shut down instead.
Because by default UEFI will enroll keys and then reboot
we also have to set --qemu-firmware-variables=custom
so it doesn't need to auto-enroll.
Because mkosi has to handle not receiving an EXIT_STATUS notification
it falls back to the exit code of qemu, which in the case of reboot
would be 0, we also override the success exit status to 123
and check that we got that as an exit code from mkosi.
