* Add multiple inheritance to kobj. Each class can have zero or more base

  classes and if a method is not found in a given class, its base classes
  are searched (in the order they were declared). This search is recursive,
  i.e. a method may be define in a base class of a base class.
* Change the kobj method lookup algorithm to one which is SMP-safe. This
  relies only on the constraint that an observer of a sequence of writes
  of pointer-sized values will see exactly one of those values, not a
  mixture of two or more values. This assumption holds for all processors
  which FreeBSD supports.
* Add locking to kobj class initialisation.
* Add a simpler form of 'inheritance' for devclasses. Each devclass can
  have a parent devclass. Searches for drivers continue up the chain of
  devclasses until either a matching driver is found or a devclass is
  reached which has no parent. This can allow, for instance, pci drivers
  to match cardbus devices (assuming that cardbus declares pci as its
  parent devclass).
* Increment __FreeBSD_version.

This preserves the driver API entirely except for one minor feature used
by the ISA compatibility shims. A workaround for ISA compatibility will
be committed separately. The kobj and newbus ABI has changed - all modules
must be recompiled.

1 files changed, 155 insertions, 33 deletions

diff --git a/sys/kern/subr_kobj.c b/sys/kern/subr_kobj.c
index a3fc230..1704a0f 100644
--- a/sys/kern/subr_kobj.c
+++ b/sys/kern/subr_kobj.c
@@ -1,5 +1,5 @@
 /*-
- * Copyright (c) 2000 Doug Rabson
+ * Copyright (c) 2000,2003 Doug Rabson
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -28,16 +28,15 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
-#include <sys/queue.h>
-#include <sys/malloc.h>
 #include <sys/kernel.h>
-#include <sys/module.h>
-#include <sys/errno.h>
+#include <sys/kobj.h>
+#include <sys/lock.h>
+#include <sys/malloc.h>
+#include <sys/mutex.h>
 #include <sys/sysctl.h>
 #ifndef TEST
 #include <sys/systm.h>
 #endif
-#include <sys/kobj.h>
 
 #ifdef TEST
 #include "usertest.h"
@@ -57,22 +56,43 @@ SYSCTL_UINT(_kern, OID_AUTO, kobj_misses, CTLFLAG_RD,
 
 #endif
 
+static struct mtx kobj_mtx;
 static int kobj_next_id = 1;
 
 SYSCTL_UINT(_kern, OID_AUTO, kobj_methodcount, CTLFLAG_RD,
 	   &kobj_next_id, 0, "");
 
-static int
+static void
+kobj_init_mutex(void *arg)
+{
+
+	mtx_init(&kobj_mtx, "kobj", NULL, MTX_DEF);
+}
+
+SYSINIT(kobj, SI_SUB_LOCK, SI_ORDER_ANY, kobj_init_mutex, NULL);
+
+/*
+ * This method structure is used to initialise new caches. Since the
+ * desc pointer is NULL, it is guaranteed never to match any read
+ * descriptors.
+ */
+static struct kobj_method null_method = {
+	0, 0,
+};
+
+int
 kobj_error_method(void)
 {
+
 	return ENXIO;
 }
 
 static void
 kobj_register_method(struct kobjop_desc *desc)
 {
+
+	mtx_assert(&kobj_mtx, MA_OWNED);
 	if (desc->id == 0) {
-		KASSERT((kobj_next_id < KOBJ_CACHE_SIZE), ("kobj method table overflow"));
 		desc->id = kobj_next_id++;
 	}
 }
@@ -88,6 +108,8 @@ kobj_class_compile_common(kobj_class_t cls, kobj_ops_t ops)
 	kobj_method_t *m;
 	int i;
 
+	mtx_assert(&kobj_mtx, MA_OWNED);
+
 	/*
 	 * Don't do anything if we are already compiled.
 	 */
@@ -103,7 +125,8 @@ kobj_class_compile_common(kobj_class_t cls, kobj_ops_t ops)
 	/*
 	 * Then initialise the ops table.
 	 */
-	bzero(ops, sizeof(struct kobj_ops));
+	for (i = 0; i < KOBJ_CACHE_SIZE; i++)
+		ops->cache[i] = &null_method;
 	ops->cls = cls;
 	cls->ops = ops;
 }
@@ -113,42 +136,106 @@ kobj_class_compile(kobj_class_t cls)
 {
 	kobj_ops_t ops;
 
+	mtx_assert(&kobj_mtx, MA_NOTOWNED);
+
 	/*
 	 * Allocate space for the compiled ops table.
 	 */
 	ops = malloc(sizeof(struct kobj_ops), M_KOBJ, M_NOWAIT);
 	if (!ops)
 		panic("kobj_compile_methods: out of memory");
+
+	mtx_lock(&kobj_mtx);
+	
+	/*
+	 * We may have lost a race for kobj_class_compile here - check
+	 * to make sure someone else hasn't already compiled this
+	 * class.
+	 */
+	if (cls->ops) {
+		mtx_unlock(&kobj_mtx);
+		free(ops, M_KOBJ);
+		return;
+	}
+
 	kobj_class_compile_common(cls, ops);
+	mtx_unlock(&kobj_mtx);
 }
 
 void
 kobj_class_compile_static(kobj_class_t cls, kobj_ops_t ops)
 {
+
+	mtx_assert(&kobj_mtx, MA_NOTOWNED);
+
 	/*
 	 * Increment refs to make sure that the ops table is not freed.
 	 */
+	mtx_lock(&kobj_mtx);
 	cls->refs++;
 	kobj_class_compile_common(cls, ops);
+	mtx_unlock(&kobj_mtx);
 }
 
-void
-kobj_lookup_method(kobj_method_t *methods,
-		   kobj_method_t *ce,
-		   kobjop_desc_t desc)
+static kobj_method_t*
+kobj_lookup_method_class(kobj_class_t cls, kobjop_desc_t desc)
 {
-	ce->desc = desc;
-	for (; methods && methods->desc; methods++) {
-		if (methods->desc == desc) {
-			ce->func = methods->func;
-			return;
+	kobj_method_t *methods = cls->methods;
+	kobj_method_t *ce;
+
+	for (ce = methods; ce && ce->desc; ce++) {
+		if (ce->desc == desc) {
+			return ce;
 		}
 	}
-	if (desc->deflt)
-		ce->func = desc->deflt;
-	else
-		ce->func = kobj_error_method;
-	return;
+
+	return 0;
+}
+
+static kobj_method_t*
+kobj_lookup_method_mi(kobj_class_t cls,
+		      kobjop_desc_t desc)
+{
+	kobj_method_t *ce;
+	kobj_class_t *basep;
+
+	ce = kobj_lookup_method_class(cls, desc);
+	if (ce)
+		return ce;
+
+	basep = cls->baseclasses;
+	if (basep) {
+		for (; *basep; basep++) {
+			ce = kobj_lookup_method_mi(*basep, desc);
+			if (ce)
+				return ce;
+		}
+	}
+
+	return 0;
+}
+
+kobj_method_t*
+kobj_lookup_method(kobj_class_t cls,
+		   kobj_method_t **cep,
+		   kobjop_desc_t desc)
+{
+	kobj_method_t *ce;
+
+#ifdef KOBJ_STATS
+	/*
+	 * Correct for the 'hit' assumption in KOBJOPLOOKUP and record
+	 * a 'miss'.
+	 */
+	kobj_lookup_hits--;
+	kobj_lookup_misses--;
+#endif
+
+	ce = kobj_lookup_method_mi(cls, desc);
+	if (!ce)
+		ce = desc->deflt;
+	*cep = ce;
+	return ce;
 }
 
 void
@@ -156,18 +243,33 @@ kobj_class_free(kobj_class_t cls)
 {
 	int i;
 	kobj_method_t *m;
+	void* ops = 0;
 
-	/*
-	 * Unregister any methods which are no longer used.
-	 */
-	for (i = 0, m = cls->methods; m->desc; i++, m++)
-		kobj_unregister_method(m->desc);
+	mtx_assert(&kobj_mtx, MA_NOTOWNED);
+	mtx_lock(&kobj_mtx);
 
 	/*
-	 * Free memory and clean up.
+	 * Protect against a race between kobj_create and
+	 * kobj_delete.
 	 */
-	free(cls->ops, M_KOBJ);
-	cls->ops = 0;
+	if (cls->refs == 0) {
+		/*
+		 * Unregister any methods which are no longer used.
+		 */
+		for (i = 0, m = cls->methods; m->desc; i++, m++)
+			kobj_unregister_method(m->desc);
+
+		/*
+		 * Free memory and clean up.
+		 */
+		ops = cls->ops;
+		cls->ops = 0;
+	}
+	
+	mtx_unlock(&kobj_mtx);
+
+	if (ops)
+		free(ops, M_KOBJ);
 }
 
 kobj_t
@@ -191,28 +293,48 @@ kobj_create(kobj_class_t cls,
 void
 kobj_init(kobj_t obj, kobj_class_t cls)
 {
+	mtx_assert(&kobj_mtx, MA_NOTOWNED);
+  retry:
+	mtx_lock(&kobj_mtx);
+
 	/*
 	 * Consider compiling the class' method table.
 	 */
-	if (!cls->ops)
+	if (!cls->ops) {
+		/*
+		 * kobj_class_compile doesn't want the lock held
+		 * because of the call to malloc - we drop the lock
+		 * and re-try.
+		 */
+		mtx_unlock(&kobj_mtx);
 		kobj_class_compile(cls);
+		goto retry;
+	}
 
 	obj->ops = cls->ops;
 	cls->refs++;
+
+	mtx_unlock(&kobj_mtx);
 }
 
 void
 kobj_delete(kobj_t obj, struct malloc_type *mtype)
 {
 	kobj_class_t cls = obj->ops->cls;
+	int refs;
 
 	/*
 	 * Consider freeing the compiled method table for the class
 	 * after its last instance is deleted. As an optimisation, we
 	 * should defer this for a short while to avoid thrashing.
 	 */
+	mtx_assert(&kobj_mtx, MA_NOTOWNED);
+	mtx_lock(&kobj_mtx);
 	cls->refs--;
-	if (!cls->refs)
+	refs = cls->refs;
+	mtx_unlock(&kobj_mtx);
+
+	if (!refs)
 		kobj_class_free(cls);
 
 	obj->ops = 0;