If the credential on an incoming thread is correct, don't bother

reaquiring it. In the same vein, don't bother dropping the thread cred
when goinf ot userland. We are guaranteed to nned it when we come back,
(which we are guaranteed to do).

Reviewed by:	jhb@freebsd.org, bde@freebsd.org (slightly different version)

1 files changed, 8 insertions, 6 deletions

diff --git a/sys/i386/i386/trap.c b/sys/i386/i386/trap.c
index 07067c4..bc31c8c 100644
--- a/sys/i386/i386/trap.c
+++ b/sys/i386/i386/trap.c
@@ -256,9 +256,8 @@ trap(frame)
 		sticks = td->td_kse->ke_sticks;
 		td->td_frame = &frame;
 		KASSERT(td->td_ucred == NULL, ("already have a ucred"));
-		PROC_LOCK(p);
-		td->td_ucred = crhold(p->p_ucred);
-		PROC_UNLOCK(p);
+		if (td->td_ucred != p->p_ucred) 
+			cred_update_thread(td);
 
 		switch (type) {
 		case T_PRIVINFLT:	/* privileged instruction fault */
@@ -644,10 +643,12 @@ user:
 	userret(td, &frame, sticks);
 	mtx_assert(&Giant, MA_NOTOWNED);
 userout:
+#ifdef	INVARIANTS
 	mtx_lock(&Giant);
 	crfree(td->td_ucred);
 	mtx_unlock(&Giant);
 	td->td_ucred = NULL;
+#endif
 out:
 	return;
 }
@@ -954,9 +955,8 @@ syscall(frame)
 	sticks = td->td_kse->ke_sticks;
 	td->td_frame = &frame;
 	KASSERT(td->td_ucred == NULL, ("already have a ucred"));
-	PROC_LOCK(p);
-	td->td_ucred = crhold(p->p_ucred);
-	PROC_UNLOCK(p);
+	if (td->td_ucred != p->p_ucred) 
+		cred_update_thread(td);
 	params = (caddr_t)frame.tf_esp + sizeof(int);
 	code = frame.tf_eax;
 	orig_tf_eflags = frame.tf_eflags;
@@ -1099,10 +1099,12 @@ bad:
 	 */
 	STOPEVENT(p, S_SCX, code);
 
+#ifdef	INVARIANTS
 	mtx_lock(&Giant);
 	crfree(td->td_ucred);
 	mtx_unlock(&Giant);
 	td->td_ucred = NULL;
+#endif
 #ifdef WITNESS
 	if (witness_list(td)) {
 		panic("system call %s returning with mutex(s) held\n",