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cgroup: update only siblings that got realized once

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Fixes: #14475
Replaces: #14554
This commit is contained in:
Lennart Poettering 2020-01-13 20:06:39 +01:00
parent 95ae4d1420
commit e1e98911a8
1 changed files with 16 additions and 1 deletions
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17
src/core/cgroup.c
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@ -2335,7 +2335,15 @@ static void unit_add_siblings_to_cgroup_realize_queue(Unit *u) {
Unit *slice;
/* This adds the siblings of the specified unit and the siblings of all parent units to the cgroup
* queue. (But neither the specified unit itself nor the parents.) */
* queue. (But neither the specified unit itself nor the parents.)
*
* Propagation of realization "side-ways" (i.e. towards siblings) is in relevant on cgroup-v1 where
* scheduling become very weird if two units that own processes reside in the same slice, but one is
* realized in the "cpu" hierarchy and once is not (for example because one has CPUWeight= set and
* the other does not), because that means processes need to be scheduled against groups. Let's avoid
* this asymmetry by always ensuring that units below a slice that are realized at all are hence
* always realized in *all* their hierarchies, and it is sufficient for a unit's sibling to be
* realized for a unit to be realized too. */
while ((slice = UNIT_DEREF(u->slice))) {
Iterator i;
@ -2343,6 +2351,7 @@ static void unit_add_siblings_to_cgroup_realize_queue(Unit *u) {
void *v;
HASHMAP_FOREACH_KEY(v, m, slice->dependencies[UNIT_BEFORE], i) {
/* Skip units that have a dependency on the slice but aren't actually in it. */
if (UNIT_DEREF(m->slice) != slice)
continue;
@ -2351,6 +2360,11 @@ static void unit_add_siblings_to_cgroup_realize_queue(Unit *u) {
if (UNIT_IS_INACTIVE_OR_FAILED(unit_active_state(m)))
continue;
/* We only enqueue siblings if they were realized once at least, in the main
* hierarchy. */
if (!m->cgroup_realized)
continue;
/* If the unit doesn't need any new controllers and has current ones realized, it
* doesn't need any changes. */
if (unit_has_mask_realized(m,
@ -2648,6 +2662,7 @@ void unit_add_to_cgroup_empty_queue(Unit *u) {
/* Let's verify that the cgroup is really empty */
if (!u->cgroup_path)
return;
r = cg_is_empty_recursive(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path);
if (r < 0) {
log_unit_debug_errno(u, r, "Failed to determine whether cgroup %s is empty: %m", u->cgroup_path);