From 3c426d5e114035d00453bb5d82a92826db1ed71f Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 16 Oct 2012 15:03:14 -0700 Subject: [PATCH] cgroup_freezer: don't stall transition to FROZEN for PF_NOFREEZE or PF_FREEZER_SKIP tasks cgroup_freezer doesn't transition from FREEZING to FROZEN if the cgroup contains PF_NOFREEZE tasks or tasks sleeping with PF_FREEZER_SKIP set. Only kernel tasks can be non-freezable (PF_NOFREEZE) and there's nothing cgroup_freezer or userland can do about or to it. It's pointless to stall the transition for PF_NOFREEZE tasks. PF_FREEZER_SKIP indicates that the task can be skipped when determining whether frozen state is reached. A task with PF_FREEZER_SKIP is guaranteed to perform try_to_freeze() after it wakes up and can be considered frozen much like stopped or traced tasks. Note that a vfork parent uses PF_FREEZER_SKIP while waiting for the child. This updates update_if_frozen() such that it only considers freezable tasks and treats %true freezer_should_skip() tasks as frozen. This allows cgroups w/ kthreads and vfork parents successfully reach FROZEN state. Signed-off-by: Tejun Heo Cc: Oleg Nesterov Cc: Rafael J. Wysocki --- kernel/cgroup_freezer.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index 05d52185139c..557f3678c4e4 100644 --- a/kernel/cgroup_freezer.c +++ b/kernel/cgroup_freezer.c @@ -214,10 +214,18 @@ static void update_if_frozen(struct cgroup *cgroup, cgroup_iter_start(cgroup, &it); while ((task = cgroup_iter_next(cgroup, &it))) { - ntotal++; - if (freezing(task) && (frozen(task) || - task_is_stopped_or_traced(task))) - nfrozen++; + if (freezing(task)) { + ntotal++; + /* + * freezer_should_skip() indicates that the task + * should be skipped when determining freezing + * completion. Consider it frozen in addition to + * the usual frozen condition. + */ + if (frozen(task) || task_is_stopped_or_traced(task) || + freezer_should_skip(task)) + nfrozen++; + } } if (old_state == CGROUP_THAWED) { -- 2.20.1