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| author | Matt Helsley <matthltc@us.ibm.com> | 2010-05-10 23:18:47 +0200 |
|---|---|---|
| committer | Rafael J. Wysocki <rjw@sisk.pl> | 2010-05-10 23:18:47 +0200 |
| commit | 8f77578cc2debaeb30a4ef6206f4ba10944bdcd8 (patch) | |
| tree | 796fdc066d523a9827a5aec0ae4276710fb8181b | |
| parent | 543f2503a956601dd490c6cde0ebf6adb4653e50 (diff) | |
| download | lwn-8f77578cc2debaeb30a4ef6206f4ba10944bdcd8.tar.gz lwn-8f77578cc2debaeb30a4ef6206f4ba10944bdcd8.zip | |
Freezer / cgroup freezer: Update stale locking comments
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@us.ibm.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
| -rw-r--r-- | kernel/cgroup_freezer.c | 21 |
1 files changed, 13 insertions, 8 deletions
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index e5c0244962b0..ce71ed53e88f 100644 --- a/kernel/cgroup_freezer.c +++ b/kernel/cgroup_freezer.c @@ -89,10 +89,10 @@ struct cgroup_subsys freezer_subsys; /* Locks taken and their ordering * ------------------------------ - * css_set_lock * cgroup_mutex (AKA cgroup_lock) - * task->alloc_lock (AKA task_lock) * freezer->lock + * css_set_lock + * task->alloc_lock (AKA task_lock) * task->sighand->siglock * * cgroup code forces css_set_lock to be taken before task->alloc_lock @@ -100,33 +100,38 @@ struct cgroup_subsys freezer_subsys; * freezer_create(), freezer_destroy(): * cgroup_mutex [ by cgroup core ] * - * can_attach(): - * cgroup_mutex + * freezer_can_attach(): + * cgroup_mutex (held by caller of can_attach) * - * cgroup_frozen(): + * cgroup_freezing_or_frozen(): * 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) * * freezer_read(): * cgroup_mutex * freezer->lock + * write_lock css_set_lock (cgroup iterator start) + * task->alloc_lock * read_lock css_set_lock (cgroup iterator start) * * freezer_write() (freeze): * cgroup_mutex * freezer->lock + * write_lock css_set_lock (cgroup iterator start) + * task->alloc_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 + * write_lock css_set_lock (cgroup iterator start) + * task->alloc_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, |