Change the way we ensure td_ucred is NULL if DIAGNOSTIC is defined.

Instead of caching the ucred reference, just go ahead and eat the
decerement and increment of the refcount.  Now that Giant is pushed down
into crfree(), we no longer have to get Giant in the common case.  In the
case when we are actually free'ing the ucred, we would normally free it on
the next kernel entry, so the cost there is not new, just in a different
place.  This also removse td_cache_ucred from struct thread.  This is
still only done #ifdef DIAGNOSTIC.

Tested on:	i386, alpha

1 files changed, 6 insertions, 25 deletions

diff --git a/sys/i386/i386/trap.c b/sys/i386/i386/trap.c
index 57d1dea..751d5f5 100644
--- a/sys/i386/i386/trap.c
+++ b/sys/i386/i386/trap.c
@@ -257,13 +257,6 @@ trap(frame)
 
 		sticks = td->td_kse->ke_sticks;
 		td->td_frame = &frame;
-#ifdef DIAGNOSTIC
-		/* see the comment in ast() */
-		if (td->td_ucred != NULL)
-			panic("trap(): thread got a ucred while in userspace");
-		td->td_ucred = td->td_ucred_cache;
-		td->td_ucred_cache = NULL;
-#endif
 		if (td->td_ucred != p->p_ucred) 
 			cred_update_thread(td);
 
@@ -651,12 +644,9 @@ user:
 	userret(td, &frame, sticks);
 	mtx_assert(&Giant, MA_NOTOWNED);
 userout:
-#ifdef DIAGNOSTIC 			/* see the comment in ast() */
-	if (td->td_ucred_cache)
-		panic("trap:thread already has cached ucred");
-	td->td_ucred_cache = td->td_ucred;
-        td->td_ucred = NULL;
-#endif /* DIAGNOSTIC */
+#ifdef DIAGNOSTIC
+	cred_free_thread(td);
+#endif
 out:
 	return;
 }
@@ -964,12 +954,6 @@ syscall(frame)
 
 	sticks = td->td_kse->ke_sticks;
 	td->td_frame = &frame;
-#ifdef DIAGNOSTIC 			/* see the comment in ast() */
-	if (td->td_ucred)
-		panic("trap:thread got a cred while userspace");
-	td->td_ucred = td->td_ucred_cache;
-	td->td_ucred_cache = NULL;
-#endif /* DIAGNOSTIC */
 	if (td->td_ucred != p->p_ucred) 
 		cred_update_thread(td);
 	params = (caddr_t)frame.tf_esp + sizeof(int);
@@ -1114,12 +1098,9 @@ bad:
 	 */
 	STOPEVENT(p, S_SCX, code);
 
-#ifdef DIAGNOSTIC 			/* see the comment in ast() */
-	if (td->td_ucred_cache)
-		panic("syscall:thread already has cached ucred");
-	td->td_ucred_cache = td->td_ucred;
-        td->td_ucred = NULL;
-#endif /* DIAGNOSTIC */
+#ifdef DIAGNOSTIC
+	cred_free_thread(td);
+#endif
 
 #ifdef WITNESS
 	if (witness_list(td)) {