On Mon, 1 Dec 2014, David Herrmann wrote:
Hi
On Sat, Nov 29, 2014 at 12:35 PM, Ross Lagerwall
<rosslagerw...@gmail.com> wrote:
Hi,
On recent versions of systemd, unit_kill_context doesn't set
wait_for_exit to true which means that service_enter_signal sends
SIGTERM, immediately moves into stop-sigkill and sends SIGKILL, ignoring
TimeoutStopSec and often killing processes without giving them a chance
to cleanup.
Reverting the following change, fixes the problem:
commit 1baccdda2e954214e0c5463d6ed8f06009b33c41
Author: Lennart Poettering <lenn...@poettering.net>
Date: Wed Feb 5 02:22:11 2014 +0100
core: don't wait for non-control/non-main processes when killing processes
on the host either
Since the current kernel cgroup notification logic is easily confused by
existing subgroups, let's do the same thing as in containers before. and
just not wait for non-control and non-main processes.
This should be corrected as soon as we have sane cgroup notifications
from the kernel.
The commit-message and the comment it adds should answer your
question: The kernel cgroup API does not allow us to wait for
non-control processes. That is, we still honor TimeoutStopSec and
friends if we have to wait for the main-process and/or control process
(in those cases, wait_for_exit is still set to true). However, if
there are other processes remaining in the cgroup, we now ignore it.
See the commit you mentioned for an explanation.
What specifically would happen if wait_for_exit were kept true for other
processes in the cgroup?
As far as I can see they would continue to be watched for SIGCHLD (since
unit_watch_all_pids should have been previously called on the unit). PID 1
may or may not get SIGCHLD for them, depending on whether they got
reparented before they exited. Each time systemd gets a SIGCHLD, it can
use unit_tidy_watch_pids to check the unit's entire PID list to see which
ones are still present.
So at best we see the PIDs go away one by one in the cgroup, and we know
when it's empty ourselves. At worst we don't see the last PID's SIGCHLD,
so we have to wait the entire TimeoutStopSec interval before discovering
that the cgroup is empty.
So I must be missing something important here, since everyone is stating
emphatically that this is unsolveable until cgroup empty notifications are
fixed. The only issue I can think of is that PIDs may be reused before the
TimeoutStopSec interval completes.
- Michael
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