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>

4 files changed, 29 insertions, 31 deletions

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 94b1e356c02a..f4544b99efe4 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -23,11 +23,10 @@ extern struct files_struct init_files;
 extern struct fs_struct init_fs;
 
 #ifdef CONFIG_CGROUPS
-#define INIT_THREADGROUP_FORK_LOCK(sig)                                 \
-        .threadgroup_fork_lock =                                        \
-                __RWSEM_INITIALIZER(sig.threadgroup_fork_lock),
+#define INIT_GROUP_RWSEM(sig)                                           \
+        .group_rwsem = __RWSEM_INITIALIZER(sig.group_rwsem),
 #else
-#define INIT_THREADGROUP_FORK_LOCK(sig)
+#define INIT_GROUP_RWSEM(sig)
 #endif
 
 #define INIT_SIGNALS(sig) {                                             \
@@ -46,7 +45,7 @@ extern struct fs_struct init_fs;
         },                                                              \
         .cred_guard_mutex =                                             \
                  __MUTEX_INITIALIZER(sig.cred_guard_mutex),             \
-        INIT_THREADGROUP_FORK_LOCK(sig)                                 \
+        INIT_GROUP_RWSEM(sig)                                           \
 }
 
 extern struct nsproxy init_nsproxy;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index d81cce933869..8cd523202a3b 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -635,13 +635,13 @@ struct signal_struct {
 #endif
 #ifdef CONFIG_CGROUPS
         /*
-         * The threadgroup_fork_lock prevents threads from forking with
+         * The group_rwsem prevents threads from forking with
          * CLONE_THREAD while held for writing. Use this for fork-sensitive
          * threadgroup-wide operations. It's taken for reading in fork.c in
          * copy_process().
          * Currently only needed write-side by cgroups.
          */
-        struct rw_semaphore threadgroup_fork_lock;
+        struct rw_semaphore group_rwsem;
 #endif
 
         int oom_adj;            /* OOM kill score adjustment (bit shift) */
@@ -2371,29 +2371,29 @@ static inline void unlock_task_sighand(struct task_struct *tsk,
         spin_unlock_irqrestore(&tsk->sighand->siglock, *flags);
 }
 
-/* See the declaration of threadgroup_fork_lock in signal_struct. */
+/* See the declaration of group_rwsem in signal_struct. */
 #ifdef CONFIG_CGROUPS
-static inline void threadgroup_fork_read_lock(struct task_struct *tsk)
+static inline void threadgroup_change_begin(struct task_struct *tsk)
 {
-        down_read(&tsk->signal->threadgroup_fork_lock);
+        down_read(&tsk->signal->group_rwsem);
 }
-static inline void threadgroup_fork_read_unlock(struct task_struct *tsk)
+static inline void threadgroup_change_end(struct task_struct *tsk)
 {
-        up_read(&tsk->signal->threadgroup_fork_lock);
+        up_read(&tsk->signal->group_rwsem);
 }
-static inline void threadgroup_fork_write_lock(struct task_struct *tsk)
+static inline void threadgroup_lock(struct task_struct *tsk)
 {
-        down_write(&tsk->signal->threadgroup_fork_lock);
+        down_write(&tsk->signal->group_rwsem);
 }
-static inline void threadgroup_fork_write_unlock(struct task_struct *tsk)
+static inline void threadgroup_unlock(struct task_struct *tsk)
 {
-        up_write(&tsk->signal->threadgroup_fork_lock);
+        up_write(&tsk->signal->group_rwsem);
 }
 #else
-static inline void threadgroup_fork_read_lock(struct task_struct *tsk) {}
-static inline void threadgroup_fork_read_unlock(struct task_struct *tsk) {}
-static inline void threadgroup_fork_write_lock(struct task_struct *tsk) {}
-static inline void threadgroup_fork_write_unlock(struct task_struct *tsk) {}
+static inline void threadgroup_change_begin(struct task_struct *tsk) {}
+static inline void threadgroup_change_end(struct task_struct *tsk) {}
+static inline void threadgroup_lock(struct task_struct *tsk) {}
+static inline void threadgroup_unlock(struct task_struct *tsk) {}
 #endif
 
 #ifndef __HAVE_THREAD_FUNCTIONS
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 6545fd61b10d..b409df3b2e9d 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);
         }
diff --git a/kernel/fork.c b/kernel/fork.c
index 827808613847..d4ac9e3e0075 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -972,7 +972,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
         sched_autogroup_fork(sig);
 
 #ifdef CONFIG_CGROUPS
-        init_rwsem(&sig->threadgroup_fork_lock);
+        init_rwsem(&sig->group_rwsem);
 #endif
 
         sig->oom_adj = current->signal->oom_adj;
@@ -1157,7 +1157,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         p->io_context = NULL;
         p->audit_context = NULL;
         if (clone_flags & CLONE_THREAD)
-                threadgroup_fork_read_lock(current);
+                threadgroup_change_begin(current);
         cgroup_fork(p);
 #ifdef CONFIG_NUMA
         p->mempolicy = mpol_dup(p->mempolicy);
@@ -1372,7 +1372,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         proc_fork_connector(p);
         cgroup_post_fork(p);
         if (clone_flags & CLONE_THREAD)
-                threadgroup_fork_read_unlock(current);
+                threadgroup_change_end(current);
         perf_event_fork(p);
         return p;
 
@@ -1407,7 +1407,7 @@ bad_fork_cleanup_policy:
 bad_fork_cleanup_cgroup:
 #endif
         if (clone_flags & CLONE_THREAD)
-                threadgroup_fork_read_unlock(current);
+                threadgroup_change_end(current);
         cgroup_exit(p, cgroup_callbacks_done);
         delayacct_tsk_free(p);
         module_put(task_thread_info(p)->exec_domain->module);