threadgroup: rename signal->threadgroup_fork_lock to ->group_rwsem

Make the following renames to prepare for extension of threadgroup
locking.

* s/signal->threadgroup_fork_lock/signal->group_rwsem/
* s/threadgroup_fork_read_lock()/threadgroup_change_begin()/
* s/threadgroup_fork_read_unlock()/threadgroup_change_end()/
* s/threadgroup_fork_write_lock()/threadgroup_lock()/
* s/threadgroup_fork_write_unlock()/threadgroup_unlock()/

This patch doesn't cause any behavior change.

-v2: Rename threadgroup_change_done() to threadgroup_change_end() per
     KAMEZAWA's suggestion.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Menage <paul@paulmenage.org>

1 files changed, 6 insertions, 7 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 6545fd61b10..b409df3b2e9 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2003,8 +2003,8 @@ static int css_set_prefetch(struct cgroup *cgrp, struct css_set *cg,
  * @cgrp: the cgroup to attach to
  * @leader: the threadgroup leader task_struct of the group to be attached
  *
- * Call holding cgroup_mutex and the threadgroup_fork_lock of the leader. Will
- * take task_lock of each thread in leader's threadgroup individually in turn.
+ * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
+ * task_lock of each thread in leader's threadgroup individually in turn.
  */
 int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
 {
@@ -2030,8 +2030,8 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
 	 * step 0: in order to do expensive, possibly blocking operations for
 	 * every thread, we cannot iterate the thread group list, since it needs
 	 * rcu or tasklist locked. instead, build an array of all threads in the
-	 * group - threadgroup_fork_lock prevents new threads from appearing,
-	 * and if threads exit, this will just be an over-estimate.
+	 * group - group_rwsem prevents new threads from appearing, and if
+	 * threads exit, this will just be an over-estimate.
 	 */
 	group_size = get_nr_threads(leader);
 	/* flex_array supports very large thread-groups better than kmalloc. */
@@ -2249,7 +2249,6 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
 			cgroup_unlock();
 			return -ESRCH;
 		}
-
 		/*
 		 * even if we're attaching all tasks in the thread group, we
 		 * only need to check permissions on one of them.
@@ -2273,9 +2272,9 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
 	}
 
 	if (threadgroup) {
-		threadgroup_fork_write_lock(tsk);
+		threadgroup_lock(tsk);
 		ret = cgroup_attach_proc(cgrp, tsk);
-		threadgroup_fork_write_unlock(tsk);
+		threadgroup_unlock(tsk);
 	} else {
 		ret = cgroup_attach_task(cgrp, tsk);
 	}