proc: get_nr_threads() doesn't need ->siglock any longer

Now that task->signal can't go away get_nr_threads() doesn't need
->siglock to read signal->count.

Also, make it inline, move into sched.h, and convert 2 other proc users of
signal->count to use this (now trivial) helper.

Henceforth get_nr_threads() is the only valid user of signal->count, we
are ready to turn it into "int nr_threads" or, perhaps, kill it.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 7 insertions, 14 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 885ab5513ac5..9b58d38bc911 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -267,7 +267,7 @@ static inline void task_sig(struct seq_file *m, struct task_struct *p)
                 shpending = p->signal->shared_pending.signal;
                 blocked = p->blocked;
                 collect_sigign_sigcatch(p, &ignored, &caught);
-                num_threads = atomic_read(&p->signal->count);
+                num_threads = get_nr_threads(p);
                 rcu_read_lock();  /* FIXME: is this correct? */
                 qsize = atomic_read(&__task_cred(p)->user->sigpending);
                 rcu_read_unlock();
@@ -410,7 +410,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
                         tty_nr = new_encode_dev(tty_devnum(sig->tty));
                 }
 
-                num_threads = atomic_read(&sig->count);
+                num_threads = get_nr_threads(task);
                 collect_sigign_sigcatch(task, &sigign, &sigcatch);
 
                 cmin_flt = sig->cmin_flt;
diff --git a/fs/proc/base.c b/fs/proc/base.c
index c7f9f23449dc..c384e8b84dff 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -166,18 +166,6 @@ static int get_fs_path(struct task_struct *task, struct path *path, bool root)
         return result;
 }
 
-static int get_nr_threads(struct task_struct *tsk)
-{
-        unsigned long flags;
-        int count = 0;
-
-        if (lock_task_sighand(tsk, &flags)) {
-                count = atomic_read(&tsk->signal->count);
-                unlock_task_sighand(tsk, &flags);
-        }
-        return count;
-}
-
 static int proc_cwd_link(struct inode *inode, struct path *path)
 {
         struct task_struct *task = get_proc_task(inode);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index dd597d8013a8..ccd2d1500720 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2147,6 +2147,11 @@ extern bool current_is_single_threaded(void);
 #define while_each_thread(g, t) \
         while ((t = next_thread(t)) != g)
 
+static inline int get_nr_threads(struct task_struct *tsk)
+{
+        return atomic_read(&tsk->signal->count);
+}
+
 /* de_thread depends on thread_group_leader not being a pid based check */
 #define thread_group_leader(p)  (p == p->group_leader)