signals: consolidate send_sigqueue and send_group_sigqueue

Both functions do the same thing after proper locking, but with
different sigpending structs, so move the common code into a helper.

After this we have 4 places that look very similar: send_sigqueue: calls
do_send_sigqueue and signal_wakeup send_group_sigqueue: calls
do_send_sigqueue and __group_complete_signal __group_send_sig_info:
calls send_signal and __group_complete_signal specific_send_sig_info:
calls send_signal and signal_wakeup

Besides, send_signal performs actions similar to do_send_sigqueue's
and __group_complete_signal - to signal_wakeup.

It looks like they can be consolidated gracefully.

Oleg said:

  Personally, I think this change is very good.  But send_sigqueue() and
  send_group_sigqueue() have a very subtle difference which I was never able
  to understand.

  Let's suppose that sigqueue is already queued, and the signal is ignored
  (the latter means we should re-schedule cpu timer or handle overrruns).  In
  that case send_sigqueue() returns 0, but send_group_sigqueue() returns 1.

  I think this is not the problem (in fact, I think this patch makes the
  behaviour more correct), but I hope Thomas can take a look and confirm.

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

1 files changed, 29 insertions, 57 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index 6610a95506b3..f9a52c721274 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1290,10 +1290,33 @@ void sigqueue_free(struct sigqueue *q)
         __sigqueue_free(q);
 }
 
+static int do_send_sigqueue(int sig, struct sigqueue *q, struct task_struct *t,
+                struct sigpending *pending)
+{
+        if (unlikely(!list_empty(&q->list))) {
+                /*
+                 * If an SI_TIMER entry is already queue just increment
+                 * the overrun count.
+                 */
+
+                BUG_ON(q->info.si_code != SI_TIMER);
+                q->info.si_overrun++;
+                return 0;
+        }
+
+        if (sig_ignored(t, sig))
+                return 1;
+
+        signalfd_notify(t, sig);
+        list_add_tail(&q->list, &pending->list);
+        sigaddset(&pending->signal, sig);
+        return 0;
+}
+
 int send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
 {
         unsigned long flags;
-        int ret = 0;
+        int ret = -1;
 
         BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
 
@@ -1307,37 +1330,14 @@ int send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
          */
         rcu_read_lock();
 
-        if (!likely(lock_task_sighand(p, &flags))) {
-                ret = -1;
+        if (!likely(lock_task_sighand(p, &flags)))
                 goto out_err;
-        }
 
-        if (unlikely(!list_empty(&q->list))) {
-                /*
-                 * If an SI_TIMER entry is already queue just increment
-                 * the overrun count.
-                 */
-                BUG_ON(q->info.si_code != SI_TIMER);
-                q->info.si_overrun++;
-                goto out;
-        }
-        /* Short-circuit ignored signals.  */
-        if (sig_ignored(p, sig)) {
-                ret = 1;
-                goto out;
-        }
-        /*
-         * Deliver the signal to listening signalfds. This must be called
-         * with the sighand lock held.
-         */
-        signalfd_notify(p, sig);
+        ret = do_send_sigqueue(sig, q, p, &p->pending);
 
-        list_add_tail(&q->list, &p->pending.list);
-        sigaddset(&p->pending.signal, sig);
         if (!sigismember(&p->blocked, sig))
                 signal_wake_up(p, sig == SIGKILL);
 
-out:
         unlock_task_sighand(p, &flags);
 out_err:
         rcu_read_unlock();
@@ -1349,7 +1349,7 @@ int
 send_group_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
 {
         unsigned long flags;
-        int ret = 0;
+        int ret;
 
         BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
 
@@ -1358,38 +1358,10 @@ send_group_sigqueue(int sig, struct sigqueue *q, struct task_struct *p)
         spin_lock_irqsave(&p->sighand->siglock, flags);
         handle_stop_signal(sig, p);
 
-        /* Short-circuit ignored signals.  */
-        if (sig_ignored(p, sig)) {
-                ret = 1;
-                goto out;
-        }
-
-        if (unlikely(!list_empty(&q->list))) {
-                /*
-                 * If an SI_TIMER entry is already queue just increment
-                 * the overrun count.  Other uses should not try to
-                 * send the signal multiple times.
-                 */
-                BUG_ON(q->info.si_code != SI_TIMER);
-                q->info.si_overrun++;
-                goto out;
-        } 
-        /*
-         * Deliver the signal to listening signalfds. This must be called
-         * with the sighand lock held.
-         */
-        signalfd_notify(p, sig);
-
-        /*
-         * Put this signal on the shared-pending queue.
-         * We always use the shared queue for process-wide signals,
-         * to avoid several races.
-         */
-        list_add_tail(&q->list, &p->signal->shared_pending.list);
-        sigaddset(&p->signal->shared_pending.signal, sig);
+        ret = do_send_sigqueue(sig, q, p, &p->signal->shared_pending);
 
         __group_complete_signal(sig, p);
-out:
+
         spin_unlock_irqrestore(&p->sighand->siglock, flags);
         read_unlock(&tasklist_lock);
         return ret;