6 files changed, 178 insertions, 4 deletions
diff --git a/lib/Kconfig b/lib/Kconfig
index 71d9f81f6ee..65561716c16 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -48,6 +48,16 @@ config STMP_DEVICE
 config PERCPU_RWSEM
 	boolean
 
+config ARCH_USE_CMPXCHG_LOCKREF
+	bool
+
+config CMPXCHG_LOCKREF
+	def_bool y if ARCH_USE_CMPXCHG_LOCKREF
+	depends on SMP
+	depends on !GENERIC_LOCKBREAK
+	depends on !DEBUG_SPINLOCK
+	depends on !DEBUG_LOCK_ALLOC
+
 config CRC_CCITT
 	tristate "CRC-CCITT functions"
 	help
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1501aa55322..444e1c12fea 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -981,6 +981,25 @@ config DEBUG_KOBJECT
 	  If you say Y here, some extra kobject debugging messages will be sent
 	  to the syslog. 
 
+config DEBUG_KOBJECT_RELEASE
+	bool "kobject release debugging"
+	depends on DEBUG_KERNEL
+	help
+	  kobjects are reference counted objects.  This means that their
+	  last reference count put is not predictable, and the kobject can
+	  live on past the point at which a driver decides to drop it's
+	  initial reference to the kobject gained on allocation.  An
+	  example of this would be a struct device which has just been
+	  unregistered.
+
+	  However, some buggy drivers assume that after such an operation,
+	  the memory backing the kobject can be immediately freed.  This
+	  goes completely against the principles of a refcounted object.
+
+	  If you say Y here, the kernel will delay the release of kobjects
+	  on the last reference count to improve the visibility of this
+	  kind of kobject release bug.
+
 config HAVE_DEBUG_BUGVERBOSE
 	bool
 
diff --git a/lib/Makefile b/lib/Makefile
index 7baccfd8a4e..f2cb3082697 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -20,6 +20,7 @@ lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
 
 lib-y	+= kobject.o klist.o
+obj-y	+= lockref.o
 
 obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
 	 bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 99fec3ae405..c37aeacd765 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -309,7 +309,7 @@ static int ddebug_parse_query(char *words[], int nwords,
 			struct ddebug_query *query, const char *modname)
 {
 	unsigned int i;
-	int rc;
+	int rc = 0;
 
 	/* check we have an even number of words */
 	if (nwords % 2 != 0) {
diff --git a/lib/kobject.c b/lib/kobject.c
index 4a1f33d4354..1d46c151a4a 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -545,8 +545,8 @@ static void kobject_cleanup(struct kobject *kobj)
 	struct kobj_type *t = get_ktype(kobj);
 	const char *name = kobj->name;
 
-	pr_debug("kobject: '%s' (%p): %s\n",
-		 kobject_name(kobj), kobj, __func__);
+	pr_debug("kobject: '%s' (%p): %s, parent %p\n",
+		 kobject_name(kobj), kobj, __func__, kobj->parent);
 
 	if (t && !t->release)
 		pr_debug("kobject: '%s' (%p): does not have a release() "
@@ -580,9 +580,25 @@ static void kobject_cleanup(struct kobject *kobj)
 	}
 }
 
+#ifdef CONFIG_DEBUG_KOBJECT_RELEASE
+static void kobject_delayed_cleanup(struct work_struct *work)
+{
+	kobject_cleanup(container_of(to_delayed_work(work),
+				     struct kobject, release));
+}
+#endif
+
 static void kobject_release(struct kref *kref)
 {
-	kobject_cleanup(container_of(kref, struct kobject, kref));
+	struct kobject *kobj = container_of(kref, struct kobject, kref);
+#ifdef CONFIG_DEBUG_KOBJECT_RELEASE
+	pr_debug("kobject: '%s' (%p): %s, parent %p (delayed)\n",
+		 kobject_name(kobj), kobj, __func__, kobj->parent);
+	INIT_DELAYED_WORK(&kobj->release, kobject_delayed_cleanup);
+	schedule_delayed_work(&kobj->release, HZ);
+#else
+	kobject_cleanup(kobj);
+#endif
 }
 
 /**
diff --git a/lib/lockref.c b/lib/lockref.c
new file mode 100644
index 00000000000..9d76f404ce9
--- /dev/null
+++ b/lib/lockref.c
@@ -0,0 +1,128 @@
+#include <linux/export.h>
+#include <linux/lockref.h>
+
+#ifdef CONFIG_CMPXCHG_LOCKREF
+
+/*
+ * Note that the "cmpxchg()" reloads the "old" value for the
+ * failure case.
+ */
+#define CMPXCHG_LOOP(CODE, SUCCESS) do {					\
+	struct lockref old;							\
+	BUILD_BUG_ON(sizeof(old) != 8);						\
+	old.lock_count = ACCESS_ONCE(lockref->lock_count);			\
+	while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) {  	\
+		struct lockref new = old, prev = old;				\
+		CODE								\
+		old.lock_count = cmpxchg(&lockref->lock_count,			\
+					 old.lock_count, new.lock_count);	\
+		if (likely(old.lock_count == prev.lock_count)) {		\
+			SUCCESS;						\
+		}								\
+		cpu_relax();							\
+	}									\
+} while (0)
+
+#else
+
+#define CMPXCHG_LOOP(CODE, SUCCESS) do { } while (0)
+
+#endif
+
+/**
+ * lockref_get - Increments reference count unconditionally
+ * @lockcnt: pointer to lockref structure
+ *
+ * This operation is only valid if you already hold a reference
+ * to the object, so you know the count cannot be zero.
+ */
+void lockref_get(struct lockref *lockref)
+{
+	CMPXCHG_LOOP(
+		new.count++;
+	,
+		return;
+	);
+
+	spin_lock(&lockref->lock);
+	lockref->count++;
+	spin_unlock(&lockref->lock);
+}
+EXPORT_SYMBOL(lockref_get);
+
+/**
+ * lockref_get_not_zero - Increments count unless the count is 0
+ * @lockcnt: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count was zero
+ */
+int lockref_get_not_zero(struct lockref *lockref)
+{
+	int retval;
+
+	CMPXCHG_LOOP(
+		new.count++;
+		if (!old.count)
+			return 0;
+	,
+		return 1;
+	);
+
+	spin_lock(&lockref->lock);
+	retval = 0;
+	if (lockref->count) {
+		lockref->count++;
+		retval = 1;
+	}
+	spin_unlock(&lockref->lock);
+	return retval;
+}
+EXPORT_SYMBOL(lockref_get_not_zero);
+
+/**
+ * lockref_get_or_lock - Increments count unless the count is 0
+ * @lockcnt: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count was zero
+ * and we got the lock instead.
+ */
+int lockref_get_or_lock(struct lockref *lockref)
+{
+	CMPXCHG_LOOP(
+		new.count++;
+		if (!old.count)
+			break;
+	,
+		return 1;
+	);
+
+	spin_lock(&lockref->lock);
+	if (!lockref->count)
+		return 0;
+	lockref->count++;
+	spin_unlock(&lockref->lock);
+	return 1;
+}
+EXPORT_SYMBOL(lockref_get_or_lock);
+
+/**
+ * lockref_put_or_lock - decrements count unless count <= 1 before decrement
+ * @lockcnt: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken
+ */
+int lockref_put_or_lock(struct lockref *lockref)
+{
+	CMPXCHG_LOOP(
+		new.count--;
+		if (old.count <= 1)
+			break;
+	,
+		return 1;
+	);
+
+	spin_lock(&lockref->lock);
+	if (lockref->count <= 1)
+		return 0;
+	lockref->count--;
+	spin_unlock(&lockref->lock);
+	return 1;
+}
+EXPORT_SYMBOL(lockref_put_or_lock);