Optimized the check for unmasked pending signals in CURSIG() using a new

inline function sigsetmasked() and a new macro SIGPENDING().  CURSIG()
will soon be moved out of the normal path of execution for syscalls and
traps.  Then its efficiency will be less important but the new interfaces
will be useful for checking for unmasked pending signals in more places.

Submitted by:		luoqi (long ago, in a slightly different form)

Assert that sched_lock is not held in CURSIG().

2 files changed, 25 insertions, 8 deletions

diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 8c75985..bfefd24 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -174,16 +174,10 @@ static int sigproptbl[NSIG] = {
 int
 CURSIG(struct proc *p)
 {
-	sigset_t tmpset;
 
 	PROC_LOCK_ASSERT(p, MA_OWNED);
-	if (SIGISEMPTY(p->p_siglist))
-		return (0);
-	tmpset = p->p_siglist;
-	SIGSETNAND(tmpset, p->p_sigmask);
-	if (SIGISEMPTY(tmpset) && (p->p_flag & P_TRACED) == 0)
-		return (0);
-	return (issignal(p));
+	mtx_assert(&sched_lock, MA_NOTOWNED);
+	return (SIGPENDING(p) ? issignal(p) : 0);
 }
 
 static __inline int
diff --git a/sys/sys/signalvar.h b/sys/sys/signalvar.h
index 19abed3..77923c2 100644
--- a/sys/sys/signalvar.h
+++ b/sys/sys/signalvar.h
@@ -189,6 +189,29 @@ __sigseteq(sigset_t *set1, sigset_t *set2)
 
 #ifdef _KERNEL
 
+/* Return nonzero if process p has an unmasked pending signal. */
+#define	SIGPENDING(p)							\
+	(!SIGISEMPTY((p)->p_siglist) &&					\
+	    (!sigsetmasked(&(p)->p_siglist, &(p)->p_sigmask) ||		\
+	    (p)->p_flag & P_TRACED))
+
+/*
+ * Return the value of the pseudo-expression ((*set & ~*mask) != 0).  This
+ * is an optimized version of SIGISEMPTY() on a temporary variable
+ * containing SIGSETNAND(*set, *mask).
+ */
+static __inline int
+sigsetmasked(sigset_t *set, sigset_t *mask)
+{
+	int i;
+
+	for (i = 0; i < _SIG_WORDS; i++) {
+		if (set->__bits[i] & ~mask->__bits[i])
+			return (0);
+	}
+	return (1);
+}
+
 struct pgrp;
 struct thread;
 struct proc;