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.

MFC after:	1 week

1 files changed, 4 insertions, 5 deletions

diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index 53182db..91d161d 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -621,18 +621,17 @@ 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);