allow_signal: kill the bogus ->mm check, add a note about CLONE_SIGHAND

87245135 · Oleg Nesterov <[email protected]> · 2009-06-17 16:27:23 -07:00

allow_signal() checks ->mm == NULL.  Not sure why.  Perhaps to make sure
current is the kernel thread.  But this helper must not be used unless we
are the kernel thread, kill this check.

Also, document the fact that the CLONE_SIGHAND kthread must not use
allow_signal(), unless the caller really wants to change the parent's
->sighand->action as well.

Signed-off-by: Oleg Nesterov <[email protected]>
Acked-by: Roland McGrath <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: 87245135d5057edd5a8037131f81eeffd76d4fef
Parents: 2ffebca6

Changes

1 files changed · +9 −10

File	Status	Add	Del	Content
kernel/exit.c	modified	+9	−10	View file

kernel/exit.c

View file

diff --git a/kernel/exit.c b/kernel/exit.c
index b6c90b5..533e5f8 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -375,9 +375,8 @@ static void set_special_pids(struct pid *pid)
 }
 
 /*
- * Let kernel threads use this to say that they
- * allow a certain signal (since daemonize() will
- * have disabled all of them by default).
+ * Let kernel threads use this to say that they allow a certain signal.
+ * Must not be used if kthread was cloned with CLONE_SIGHAND.
  */
 int allow_signal(int sig)
 {
@@ -385,14 +384,14 @@ int allow_signal(int sig)
 		return -EINVAL;
 
 	spin_lock_irq(&current->sighand->siglock);
+	/* This is only needed for daemonize()'ed kthreads */
 	sigdelset(&current->blocked, sig);
-	if (!current->mm) {
-		/* Kernel threads handle their own signals.
-		   Let the signal code know it'll be handled, so
-		   that they don't get converted to SIGKILL or
-		   just silently dropped */
-		current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
-	}
+	/*
+	 * Kernel threads handle their own signals. Let the signal code
+	 * know it'll be handled, so that they don't get converted to
+	 * SIGKILL or just silently dropped.
+	 */
+	current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
 	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 	return 0;