[Devel] [PATCH] cgroup freezer: Update stale comments

[Matt Helsley]

Update stale comments regarding locking order and add a little more detail
so it's easier to follow the locking between the cgroup freezer and the
power management freezer code.

Signed-off-by: Matt Helsley <matthltc at us.ibm.com>

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index fb249e2..c2bb4aa 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -87,8 +87,8 @@ struct cgroup_subsys freezer_subsys;
  * ------------------------------
  * css_set_lock
  * cgroup_mutex (AKA cgroup_lock)
- * task->alloc_lock (AKA task_lock)
  * freezer->lock
+ * task->alloc_lock (AKA task_lock)
  * task->sighand->siglock
  *
  * cgroup code forces css_set_lock to be taken before task->alloc_lock
@@ -103,7 +103,6 @@ struct cgroup_subsys freezer_subsys;
  * task->alloc_lock (to get task's cgroup)
  *
  * freezer_fork() (preserving fork() performance means can't take cgroup_mutex):
- * task->alloc_lock (to get task's cgroup)
  * freezer->lock
  *  sighand->siglock (if the cgroup is freezing)
  *
@@ -116,13 +115,13 @@ struct cgroup_subsys freezer_subsys;
  * cgroup_mutex
  *  freezer->lock
  *   read_lock css_set_lock (cgroup iterator start)
- *    sighand->siglock
+ *    sighand->siglock (fake signal delivery inside freeze_task())
  *
  * freezer_write() (unfreeze):
  * cgroup_mutex
  *  freezer->lock
  *   read_lock css_set_lock (cgroup iterator start)
- *    task->alloc_lock (to prevent races with freeze_task())
+ *    task->alloc_lock (inside thaw_process(), prevents race with refrigerator())
  *     sighand->siglock
  */
 static struct cgroup_subsys_state *freezer_create(struct cgroup_subsys *ss,
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