signalfd simplification

This simplifies signalfd code, by avoiding it to remain attached to the
sighand during its lifetime.

In this way, the signalfd remain attached to the sighand only during
poll(2) (and select and epoll) and read(2).  This also allows to remove
all the custom "tsk == current" checks in kernel/signal.c, since
dequeue_signal() will only be called by "current".

I think this is also what Ben was suggesting time ago.

The external effect of this, is that a thread can extract only its own
private signals and the group ones.  I think this is an acceptable
behaviour, in that those are the signals the thread would be able to
fetch w/out signalfd.

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 36 deletions

diff --git a/include/linux/signalfd.h b/include/linux/signalfd.h
index 5104294..4c9ff09 100644
--- a/include/linux/signalfd.h
+++ b/include/linux/signalfd.h
@@ -45,49 +45,17 @@ struct signalfd_siginfo {
 #ifdef CONFIG_SIGNALFD
 
 /*
- * Deliver the signal to listening signalfd. This must be called
- * with the sighand lock held. Same are the following that end up
- * calling signalfd_deliver().
- */
-void signalfd_deliver(struct task_struct *tsk, int sig);
-
-/*
- * No need to fall inside signalfd_deliver() if no signal listeners
- * are available.
+ * Deliver the signal to listening signalfd.
  */
 static inline void signalfd_notify(struct task_struct *tsk, int sig)
 {
-	if (unlikely(!list_empty(&tsk->sighand->signalfd_list)))
-		signalfd_deliver(tsk, sig);
-}
-
-/*
- * The signal -1 is used to notify the signalfd that the sighand
- * is on its way to be detached.
- */
-static inline void signalfd_detach_locked(struct task_struct *tsk)
-{
-	if (unlikely(!list_empty(&tsk->sighand->signalfd_list)))
-		signalfd_deliver(tsk, -1);
-}
-
-static inline void signalfd_detach(struct task_struct *tsk)
-{
-	struct sighand_struct *sighand = tsk->sighand;
-
-	if (unlikely(!list_empty(&sighand->signalfd_list))) {
-		spin_lock_irq(&sighand->siglock);
-		signalfd_deliver(tsk, -1);
-		spin_unlock_irq(&sighand->siglock);
-	}
+	if (unlikely(waitqueue_active(&tsk->sighand->signalfd_wqh)))
+		wake_up(&tsk->sighand->signalfd_wqh);
 }
 
 #else /* CONFIG_SIGNALFD */
 
-#define signalfd_deliver(t, s) do { } while (0)
-#define signalfd_notify(t, s) do { } while (0)
-#define signalfd_detach_locked(t) do { } while (0)
-#define signalfd_detach(t) do { } while (0)
+static inline void signalfd_notify(struct task_struct *tsk, int sig) { }
 
 #endif /* CONFIG_SIGNALFD */