signals: use HAVE_SET_RESTORE_SIGMASK

Change all the #ifdef TIF_RESTORE_SIGMASK conditionals in non-arch code to
#ifdef HAVE_SET_RESTORE_SIGMASK.  If arch code defines it first, the generic
set_restore_sigmask() using TIF_RESTORE_SIGMASK is not defined.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index fe970cd..86e6079 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1175,7 +1175,7 @@
 	struct sighand_struct *sighand;
 
 	sigset_t blocked, real_blocked;
-	sigset_t saved_sigmask;		/* To be restored with TIF_RESTORE_SIGMASK */
+	sigset_t saved_sigmask;	/* restored if set_restore_sigmask() was used */
 	struct sigpending pending;
 
 	unsigned long sas_ss_sp;
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 81c5f82..38a5647 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -92,7 +92,13 @@
 #define set_need_resched()	set_thread_flag(TIF_NEED_RESCHED)
 #define clear_need_resched()	clear_thread_flag(TIF_NEED_RESCHED)
 
-#ifdef TIF_RESTORE_SIGMASK
+#if defined TIF_RESTORE_SIGMASK && !defined HAVE_SET_RESTORE_SIGMASK
+/*
+ * An arch can define its own version of set_restore_sigmask() to get the
+ * job done however works, with or without TIF_RESTORE_SIGMASK.
+ */
+#define HAVE_SET_RESTORE_SIGMASK	1
+
 /**
  * set_restore_sigmask() - make sure saved_sigmask processing gets done
  *
@@ -109,7 +115,7 @@
 	set_thread_flag(TIF_RESTORE_SIGMASK);
 	set_thread_flag(TIF_SIGPENDING);
 }
-#endif	/* TIF_RESTORE_SIGMASK */
+#endif	/* TIF_RESTORE_SIGMASK && !HAVE_SET_RESTORE_SIGMASK */
 
 #endif	/* __KERNEL__ */