signals: unify send_sigqueue/send_group_sigqueue completely

Suggested by Pavel Emelyanov.

send_sigqueue/send_group_sigqueue are only differ in how they lock ->siglock.
Unify them.  send_group_sigqueue() uses spin_lock() because it knows the task
can't exit, but in that case lock_task_sighand() can't fail and doesn't hurt.

Note that the "sig" argument is ignored, it is always equal to ->si_signo.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 21 insertions, 37 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 87424f7a4f3d..367c6662b12f 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1240,14 +1240,27 @@ void sigqueue_free(struct sigqueue *q)
         __sigqueue_free(q);
 }
 
-static int do_send_sigqueue(int sig, struct sigqueue *q, struct task_struct *t,
+static int do_send_sigqueue(struct sigqueue *q, struct task_struct *t,
                                 int group)
 {
+        int sig = q->info.si_signo;
         struct sigpending *pending;
+        unsigned long flags;
+        int ret;
 
         BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
+
+        ret = -1;
+        if (!likely(lock_task_sighand(t, &flags)))
+                goto ret;
+
         handle_stop_signal(sig, t);
 
+        ret = 1;
+        if (sig_ignored(t, sig))
+                goto out;
+
+        ret = 0;
         if (unlikely(!list_empty(&q->list))) {
                 /*
                  * If an SI_TIMER entry is already queue just increment
@@ -1256,58 +1269,29 @@ static int do_send_sigqueue(int sig, struct sigqueue *q, struct task_struct *t,
 
                 BUG_ON(q->info.si_code != SI_TIMER);
                 q->info.si_overrun++;
-                return 0;
+                goto out;
         }
 
-        if (sig_ignored(t, sig))
-                return 1;
-
         signalfd_notify(t, sig);
         pending = group ? &t->signal->shared_pending : &t->pending;
         list_add_tail(&q->list, &pending->list);
         sigaddset(&pending->signal, sig);
         complete_signal(sig, t, group);
-
-        return 0;
+out:
+        unlock_task_sighand(t, &flags);
+ret:
+        return ret;
 }
 
 int send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
 {
-        unsigned long flags;
-        int ret = -1;
-
-        /*
-         * The rcu based delayed sighand destroy makes it possible to
-         * run this without tasklist lock held. The task struct itself
-         * cannot go away as create_timer did get_task_struct().
-         *
-         * We return -1, when the task is marked exiting, so
-         * posix_timer_event can redirect it to the group leader
-         */
-        if (!likely(lock_task_sighand(p, &flags)))
-                goto out_err;
-
-        ret = do_send_sigqueue(sig, q, p, 0);
-
-        unlock_task_sighand(p, &flags);
-out_err:
-        return ret;
+        return do_send_sigqueue(q, p, 0);
 }
 
 int
 send_group_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
 {
-        unsigned long flags;
-        int ret;
-
-        /* Since it_lock is held, p->sighand cannot be NULL. */
-        spin_lock_irqsave(&p->sighand->siglock, flags);
-
-        ret = do_send_sigqueue(sig, q, p, 1);
-
-        spin_unlock_irqrestore(&p->sighand->siglock, flags);
-
-        return ret;
+        return do_send_sigqueue(q, p, 1);
 }
 
 /*