signals: introduce kernel_sigaction()

Now that allow_signal() is really trivial we can unify it with
disallow_signal().  Add the new helper, kernel_sigaction(), and
reimplement allow_signal/disallow_signal as a trivial wrappers.

This saves one EXPORT_SYMBOL() and the new helper can have more users.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 2 deletions

diff --git a/include/linux/signal.h b/include/linux/signal.h
index ac83c593f4b9..c9e65360c49a 100644
--- a/include/linux/signal.h
+++ b/include/linux/signal.h
@@ -284,8 +284,22 @@ extern int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka,
 extern void signal_setup_done(int failed, struct ksignal *ksig, int stepping);
 extern void signal_delivered(int sig, siginfo_t *info, struct k_sigaction *ka, struct pt_regs *regs, int stepping);
 extern void exit_signals(struct task_struct *tsk);
-extern void allow_signal(int);
-extern void disallow_signal(int);
+extern void kernel_sigaction(int, __sighandler_t);
+
+static inline void allow_signal(int sig)
+{
+	/*
+	 * 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.
+	 */
+	kernel_sigaction(sig, (__force __sighandler_t)2);
+}
+
+static inline void disallow_signal(int sig)
+{
+	kernel_sigaction(sig, SIG_IGN);
+}
 
 /*
  * Eventually that'll replace get_signal_to_deliver(); macro for now,