1 files changed, 36 insertions, 27 deletions

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 762c5d50b8fe..6ad8cb05f672 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -77,7 +77,10 @@ struct acpi_ioremap {
 	void __iomem *virt;
 	acpi_physical_address phys;
 	acpi_size size;
-	unsigned long refcount;
+	union {
+		unsigned long refcount;
+		struct rcu_work rwork;
+	} track;
 };
 
 static LIST_HEAD(acpi_ioremaps);
@@ -250,7 +253,7 @@ void __iomem *acpi_os_get_iomem(acpi_physical_address phys, unsigned int size)
 	map = acpi_map_lookup(phys, size);
 	if (map) {
 		virt = map->virt + (phys - map->phys);
-		map->refcount++;
+		map->track.refcount++;
 	}
 	mutex_unlock(&acpi_ioremap_lock);
 	return virt;
@@ -335,7 +338,7 @@ void __iomem __ref
 	/* Check if there's a suitable mapping already. */
 	map = acpi_map_lookup(phys, size);
 	if (map) {
-		map->refcount++;
+		map->track.refcount++;
 		goto out;
 	}
 
@@ -358,7 +361,7 @@ void __iomem __ref
 	map->virt = virt;
 	map->phys = pg_off;
 	map->size = pg_sz;
-	map->refcount = 1;
+	map->track.refcount = 1;
 
 	list_add_tail_rcu(&map->list, &acpi_ioremaps);
 
@@ -374,21 +377,26 @@ void *__ref acpi_os_map_memory(acpi_physical_address phys, acpi_size size)
 }
 EXPORT_SYMBOL_GPL(acpi_os_map_memory);
 
-/* Must be called with mutex_lock(&acpi_ioremap_lock) */
-static unsigned long acpi_os_drop_map_ref(struct acpi_ioremap *map)
+static void acpi_os_map_remove(struct work_struct *work)
 {
-	unsigned long refcount = --map->refcount;
+	struct acpi_ioremap *map = container_of(to_rcu_work(work),
+						struct acpi_ioremap,
+						track.rwork);
 
-	if (!refcount)
-		list_del_rcu(&map->list);
-	return refcount;
+	acpi_unmap(map->phys, map->virt);
+	kfree(map);
 }
 
-static void acpi_os_map_cleanup(struct acpi_ioremap *map)
+/* Must be called with mutex_lock(&acpi_ioremap_lock) */
+static void acpi_os_drop_map_ref(struct acpi_ioremap *map)
 {
-	synchronize_rcu_expedited();
-	acpi_unmap(map->phys, map->virt);
-	kfree(map);
+	if (--map->track.refcount)
+		return;
+
+	list_del_rcu(&map->list);
+
+	INIT_RCU_WORK(&map->track.rwork, acpi_os_map_remove);
+	queue_rcu_work(system_wq, &map->track.rwork);
 }
 
 /**
@@ -397,8 +405,8 @@ static void acpi_os_map_cleanup(struct acpi_ioremap *map)
  * @size: Size of the address range to drop a reference to.
  *
  * Look up the given virtual address range in the list of existing ACPI memory
- * mappings, drop a reference to it and unmap it if there are no more active
- * references to it.
+ * mappings, drop a reference to it and if there are no more active references
+ * to it, queue it up for later removal.
  *
  * During early init (when acpi_permanent_mmap has not been set yet) this
  * routine simply calls __acpi_unmap_table() to get the job done.  Since
@@ -408,7 +416,6 @@ static void acpi_os_map_cleanup(struct acpi_ioremap *map)
 void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size)
 {
 	struct acpi_ioremap *map;
-	unsigned long refcount;
 
 	if (!acpi_permanent_mmap) {
 		__acpi_unmap_table(virt, size);
@@ -416,23 +423,27 @@ void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size)
 	}
 
 	mutex_lock(&acpi_ioremap_lock);
+
 	map = acpi_map_lookup_virt(virt, size);
 	if (!map) {
 		mutex_unlock(&acpi_ioremap_lock);
 		WARN(true, PREFIX "%s: bad address %p\n", __func__, virt);
 		return;
 	}
-	refcount = acpi_os_drop_map_ref(map);
-	mutex_unlock(&acpi_ioremap_lock);
+	acpi_os_drop_map_ref(map);
 
-	if (!refcount)
-		acpi_os_map_cleanup(map);
+	mutex_unlock(&acpi_ioremap_lock);
 }
 EXPORT_SYMBOL_GPL(acpi_os_unmap_iomem);
 
+/**
+ * acpi_os_unmap_memory - Drop a memory mapping reference.
+ * @virt: Start of the address range to drop a reference to.
+ * @size: Size of the address range to drop a reference to.
+ */
 void __ref acpi_os_unmap_memory(void *virt, acpi_size size)
 {
-	return acpi_os_unmap_iomem((void __iomem *)virt, size);
+	acpi_os_unmap_iomem((void __iomem *)virt, size);
 }
 EXPORT_SYMBOL_GPL(acpi_os_unmap_memory);
 
@@ -461,7 +472,6 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas)
 {
 	u64 addr;
 	struct acpi_ioremap *map;
-	unsigned long refcount;
 
 	if (gas->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
 		return;
@@ -472,16 +482,15 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas)
 		return;
 
 	mutex_lock(&acpi_ioremap_lock);
+
 	map = acpi_map_lookup(addr, gas->bit_width / 8);
 	if (!map) {
 		mutex_unlock(&acpi_ioremap_lock);
 		return;
 	}
-	refcount = acpi_os_drop_map_ref(map);
-	mutex_unlock(&acpi_ioremap_lock);
+	acpi_os_drop_map_ref(map);
 
-	if (!refcount)
-		acpi_os_map_cleanup(map);
+	mutex_unlock(&acpi_ioremap_lock);
 }
 EXPORT_SYMBOL(acpi_os_unmap_generic_address);