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cgroup: add tracing points for cgroup v2 freezer

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Add cgroup:cgroup_freeze and cgroup:cgroup_unfreeze events,
which are using the existing cgroup tracing infrastructure.

Add the cgroup_event event class, which is similar to the cgroup
class, but contains an additional integer field to store a new
value (the level field is dropped).

Also add two tracing events: cgroup_notify_populated and
cgroup_notify_frozen, which are raised in a generic way using
the TRACE_CGROUP_PATH() macro.

This allows to trace cgroup state transitions and is generally
helpful for debugging the cgroup freezer code.

Signed-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Roman Gushchin
2019-04-19 10:03:08 -07:00
committed by Tejun Heo
parent 712e351787
commit 4c476d8cff
3 changed files with 71 additions and 1 deletions
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15
kernel/cgroup/freezer.c
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@@ -6,6 +6,8 @@
#include "cgroup-internal.h"
#include <trace/events/cgroup.h>
/*
* Propagate the cgroup frozen state upwards by the cgroup tree.
*/
@@ -28,6 +30,7 @@ static void cgroup_propagate_frozen(struct cgroup *cgrp, bool frozen)
cgrp->nr_descendants) {
set_bit(CGRP_FROZEN, &cgrp->flags);
cgroup_file_notify(&cgrp->events_file);
TRACE_CGROUP_PATH(notify_frozen, cgrp, 1);
desc++;
}
} else {
@@ -35,6 +38,7 @@ static void cgroup_propagate_frozen(struct cgroup *cgrp, bool frozen)
if (test_bit(CGRP_FROZEN, &cgrp->flags)) {
clear_bit(CGRP_FROZEN, &cgrp->flags);
cgroup_file_notify(&cgrp->events_file);
TRACE_CGROUP_PATH(notify_frozen, cgrp, 0);
desc++;
}
}
@@ -73,6 +77,7 @@ void cgroup_update_frozen(struct cgroup *cgrp)
clear_bit(CGRP_FROZEN, &cgrp->flags);
}
cgroup_file_notify(&cgrp->events_file);
TRACE_CGROUP_PATH(notify_frozen, cgrp, frozen);
/* Update the state of ancestor cgroups. */
cgroup_propagate_frozen(cgrp, frozen);
@@ -189,6 +194,11 @@ static void cgroup_do_freeze(struct cgroup *cgrp, bool freeze)
clear_bit(CGRP_FREEZE, &cgrp->flags);
spin_unlock_irq(&css_set_lock);
if (freeze)
TRACE_CGROUP_PATH(freeze, cgrp);
else
TRACE_CGROUP_PATH(unfreeze, cgrp);
css_task_iter_start(&cgrp->self, 0, &it);
while ((task = css_task_iter_next(&it))) {
/*
@@ -312,6 +322,9 @@ void cgroup_freeze(struct cgroup *cgrp, bool freeze)
* In both cases it's better to notify a user, that there is
* nothing to wait for.
*/
if (!applied)
if (!applied) {
TRACE_CGROUP_PATH(notify_frozen, cgrp,
test_bit(CGRP_FROZEN, &cgrp->flags));
cgroup_file_notify(&cgrp->events_file);
}
}