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

8 files changed, 36 insertions, 156 deletions

diff --git a/sys/alpha/alpha/trap.c b/sys/alpha/alpha/trap.c
index bbd1d5a..9c2ea34 100644
--- a/sys/alpha/alpha/trap.c
+++ b/sys/alpha/alpha/trap.c
@@ -297,13 +297,6 @@ trap(a0, a1, a2, entry, framep)
 	if (user)  {
 		sticks = td->td_kse->ke_sticks;
 		td->td_frame = framep;
-#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);
 	} else {
@@ -631,12 +624,9 @@ out:
 		framep->tf_regs[FRAME_SP] = alpha_pal_rdusp();
 		userret(td, framep, sticks);
 		mtx_assert(&Giant, MA_NOTOWNED);
-#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
 	}
 	return;
 
@@ -705,12 +695,6 @@ syscall(code, framep)
 	td->td_frame = framep;
 	opc = framep->tf_regs[FRAME_PC] - 4;
 	sticks = td->td_kse->ke_sticks;
-#ifdef DIAGNOSTIC 			/* see the comment in ast() */
-	if (td->td_ucred)
-		panic("syscall:thread got a cred while in 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);
 
@@ -833,12 +817,9 @@ syscall(code, framep)
 	 */
 	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)) {
 		panic("system call %s returning with mutex(s) held\n",
diff --git a/sys/amd64/amd64/trap.c b/sys/amd64/amd64/trap.c
index 57d1dea..751d5f5 100644
--- a/sys/amd64/amd64/trap.c
+++ b/sys/amd64/amd64/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)) {
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)) {
diff --git a/sys/ia64/ia64/trap.c b/sys/ia64/ia64/trap.c
index 1820435..060dcb5 100644
--- a/sys/ia64/ia64/trap.c
+++ b/sys/ia64/ia64/trap.c
@@ -323,13 +323,6 @@ trap(int vector, int imm, struct trapframe *framep)
 	if (user) {
 		sticks = td->td_kse->ke_sticks;
 		td->td_frame = framep;
-#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);
 	} else {
@@ -714,12 +707,9 @@ out:
 	if (user) {
 		userret(td, framep, sticks);
 		mtx_assert(&Giant, MA_NOTOWNED);
-#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
 	}
 	return;
 
@@ -764,12 +754,6 @@ syscall(int code, u_int64_t *args, struct trapframe *framep)
 
 	td->td_frame = framep;
 	sticks = td->td_kse->ke_sticks;
-#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);
 
@@ -876,12 +860,9 @@ syscall(int code, u_int64_t *args, struct trapframe *framep)
 	 */
 	STOPEVENT(p, S_SCX, code);
 
-#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
 #ifdef WITNESS
 	if (witness_list(td)) {
 		panic("system call %s returning with mutex(s) held\n",
diff --git a/sys/powerpc/aim/trap.c b/sys/powerpc/aim/trap.c
index 16ab7ae..6c122e6 100644
--- a/sys/powerpc/aim/trap.c
+++ b/sys/powerpc/aim/trap.c
@@ -226,13 +226,6 @@ trap(struct trapframe *frame)
 	if (user) {
 		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);
 
@@ -303,12 +296,9 @@ trap(struct trapframe *frame)
 	}
 	userret(td, frame, sticks);
 	mtx_assert(&Giant, MA_NOTOWNED);
-#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
 }
 
 void
diff --git a/sys/powerpc/powerpc/trap.c b/sys/powerpc/powerpc/trap.c
index 16ab7ae..6c122e6 100644
--- a/sys/powerpc/powerpc/trap.c
+++ b/sys/powerpc/powerpc/trap.c
@@ -226,13 +226,6 @@ trap(struct trapframe *frame)
 	if (user) {
 		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);
 
@@ -303,12 +296,9 @@ trap(struct trapframe *frame)
 	}
 	userret(td, frame, sticks);
 	mtx_assert(&Giant, MA_NOTOWNED);
-#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
 }
 
 void
diff --git a/sys/sparc64/sparc64/trap.c b/sys/sparc64/sparc64/trap.c
index 481cdab..f2eeaa6 100644
--- a/sys/sparc64/sparc64/trap.c
+++ b/sys/sparc64/sparc64/trap.c
@@ -177,13 +177,6 @@ trap(struct trapframe *tf)
 	if ((type & T_KERNEL) == 0) {
 		sticks = td->td_kse->ke_sticks;
 		td->td_frame = tf;
-#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);
  	} else {
@@ -387,12 +380,9 @@ trapsig:
 user:
 	userret(td, tf, sticks);
 	mtx_assert(&Giant, MA_NOTOWNED);
-#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:
 	CTR1(KTR_TRAP, "trap: td=%p return", td);
 	return;
@@ -548,12 +538,6 @@ syscall(struct trapframe *tf)
 
 	sticks = td->td_kse->ke_sticks;
 	td->td_frame = tf;
-#ifdef DIAGNOSTIC 			/* see the comment in ast() */
-	if (td->td_ucred)
-		panic("syscall: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);
 	code = tf->tf_global[1];
@@ -690,12 +674,9 @@ 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)) {
 		panic("system call %s returning with mutex(s) held\n",
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 58940f1..72656e8 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -289,11 +289,6 @@ struct thread {
 #define	td_endcopy td_pcb
 
 	struct ucred	*td_ucred;	/* (k) Reference to credentials. */
-#ifdef DIAGNOSTIC 			/* see the comment in ast() */
-	struct ucred	*td_ucred_cache; /* (k) hide cred here for DIAGNOSTIC */
-#else
-	void 		*td_dontuse;	/* keep the size the same if not DIAG */
-#endif
 	struct pcb	*td_pcb;	/* (k) Kernel VA of pcb and kstack. */
 	struct callout	td_slpcallout;	/* (h) Callout for sleep. */
 	struct trapframe *td_frame;	/* (k) */