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Subject[PATCH 1/6] cgroup_freezer: fix freezer->state setting bug in freezer_change_state()
Date
d02f52811d0e "cgroup_freezer: prepare for removal of TIF_FREEZE" moved
setting of freezer->state into freezer_change_state(); unfortunately,
while doing so, when it's beginning to freeze tasks, it sets the state
to CGROUP_FROZEN instead of CGROUP_FREEZING ending up skipping the
whole freezing state. Fix it.

-v2: Oleg pointed out that re-freezing FROZEN cgroup could increment
system_freezing_cnt. Fixed.

-v3: Matt pointed out that setting CGROUP_FROZEN always invoked
try_to_freeze_cgroup() regardless of the current state. Patch
updated such that the actual freeze/thaw operations are always
performed on state changes. This shouldn't make any difference
unless something is broken.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Oleg Nesterov <oleg@redhat.com>
Cc: Paul Menage <paul@paulmenage.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Matt Helsley <matthltc@us.ibm.com>
---
kernel/cgroup_freezer.c | 14 +++++++-------
1 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 4e82525..56a457a 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -308,24 +308,24 @@ static int freezer_change_state(struct cgroup *cgroup,
spin_lock_irq(&freezer->lock);

update_if_frozen(cgroup, freezer);
- if (goal_state == freezer->state)
- goto out;
-
- freezer->state = goal_state;

switch (goal_state) {
case CGROUP_THAWED:
- atomic_dec(&system_freezing_cnt);
+ if (freezer->state != CGROUP_THAWED)
+ atomic_dec(&system_freezing_cnt);
+ freezer->state = CGROUP_THAWED;
unfreeze_cgroup(cgroup, freezer);
break;
case CGROUP_FROZEN:
- atomic_inc(&system_freezing_cnt);
+ if (freezer->state == CGROUP_THAWED)
+ atomic_inc(&system_freezing_cnt);
+ freezer->state = CGROUP_FREEZING;
retval = try_to_freeze_cgroup(cgroup, freezer);
break;
default:
BUG();
}
-out:
+
spin_unlock_irq(&freezer->lock);

return retval;
--
1.7.6


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