MFC r268074:

Perform a lockless check in sigacts_shared.

It is used only during execve (i.e. singlethreaded), so there is no fear
of returning 'not shared' which soon becomes 'shared'.

While here reorganize the code a little to avoid proc lock/unlock in
shared case.

2 files changed, 5 insertions, 10 deletions

diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index 19ba76d..3738b89 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -624,18 +624,17 @@ interpret:
 	 * handlers. In execsigs(), the new process will have its signals
 	 * reset.
 	 */
-	PROC_LOCK(p);
-	oldcred = crcopysafe(p, newcred);
 	if (sigacts_shared(p->p_sigacts)) {
 		oldsigacts = p->p_sigacts;
-		PROC_UNLOCK(p);
 		newsigacts = sigacts_alloc();
 		sigacts_copy(newsigacts, oldsigacts);
-		PROC_LOCK(p);
-		p->p_sigacts = newsigacts;
 	} else
 		oldsigacts = NULL;
 
+	PROC_LOCK(p);
+	if (oldsigacts)
+		p->p_sigacts = newsigacts;
+	oldcred = crcopysafe(p, newcred);
 	/* Stop profiling */
 	stopprofclock(p);
 
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 99ca131..17a0e61 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -3463,10 +3463,6 @@ sigacts_copy(struct sigacts *dest, struct sigacts *src)
 int
 sigacts_shared(struct sigacts *ps)
 {
-	int shared;
 
-	mtx_lock(&ps->ps_mtx);
-	shared = ps->ps_refcnt > 1;
-	mtx_unlock(&ps->ps_mtx);
-	return (shared);
+	return (ps->ps_refcnt > 1);
 }