[PATCH 8/11] ACPI: Do not use krefs under a mutex in osl.c

Rafael J. Wysocki
2011-01-20T11:39:18Z

From: Rafael J. Wysocki <rjw@sisk.pl>

The reference counting of ACPI iomaps is carried out entirely under
acpi_ioremap_lock, so it is sufficient to use simple counters instead
of krefs for this purpose.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
drivers/acpi/osl.c | 36 ++++++++++++++++--------------------
1 file changed, 16 insertions(+), 20 deletions(-)

Index: linux-2.6/drivers/acpi/osl.c
===================================================================
--- linux-2.6.orig/drivers/acpi/osl.c
+++ linux-2.6/drivers/acpi/osl.c
@@ -105,7 +105,7 @@ struct acpi_ioremap {
void __iomem *virt;
acpi_physical_address phys;
acpi_size size;
- struct kref ref;
+ unsigned long refcount;
};

static LIST_HEAD(acpi_ioremaps);
@@ -319,7 +319,7 @@ acpi_os_map_memory(acpi_physical_address
/* Check if there's a suitable mapping already. */
map = acpi_map_lookup(phys, size);
if (map) {
- kref_get(&map->ref);
+ map->refcount++;
goto out;
}

@@ -342,7 +342,7 @@ acpi_os_map_memory(acpi_physical_address
map->virt = virt;
map->phys = pg_off;
map->size = pg_sz;
- kref_init(&map->ref);
+ map->refcount = 1;

list_add_tail_rcu(&map->list, &acpi_ioremaps);

@@ -352,25 +352,24 @@ acpi_os_map_memory(acpi_physical_address
}
EXPORT_SYMBOL_GPL(acpi_os_map_memory);

-static void acpi_kref_del_iomap(struct kref *ref)
+static void acpi_os_drop_map_ref(struct acpi_ioremap *map)
{
- struct acpi_ioremap *map;
-
- map = container_of(ref, struct acpi_ioremap, ref);
- list_del_rcu(&map->list);
+ if (!--map->refcount)
+ list_del_rcu(&map->list);
}

-static void acpi_os_remove_map(struct acpi_ioremap *map)
+static void acpi_os_map_cleanup(struct acpi_ioremap *map)
{
- synchronize_rcu();
- iounmap(map->virt);
- kfree(map);
+ if (!map->refcount) {
+ synchronize_rcu();
+ iounmap(map->virt);
+ kfree(map);
+ }
}

void __ref acpi_os_unmap_memory(void __iomem *virt, acpi_size size)
{
struct acpi_ioremap *map;
- int del;

if (!acpi_gbl_permanent_mmap) {
__acpi_unmap_table(virt, size);
@@ -384,11 +383,10 @@ void __ref acpi_os_unmap_memory(void __i
WARN(true, PREFIX "%s: bad address %p\n", __func__, virt);
return;
}
- del = kref_put(&map->ref, acpi_kref_del_iomap);
+ acpi_os_drop_map_ref(map);
mutex_unlock(&acpi_ioremap_lock);

- if (del)
- acpi_os_remove_map(map);
+ acpi_os_map_cleanup(map);
}
EXPORT_SYMBOL_GPL(acpi_os_unmap_memory);

@@ -418,7 +416,6 @@ static int acpi_os_map_generic_address(s
static void acpi_os_unmap_generic_address(struct acpi_generic_address *addr)
{
struct acpi_ioremap *map;
- int del;

if (addr->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
return;
@@ -432,11 +429,10 @@ static void acpi_os_unmap_generic_addres
mutex_unlock(&acpi_ioremap_lock);
return;
}
- del = kref_put(&map->ref, acpi_kref_del_iomap);
+ acpi_os_drop_map_ref(map);
mutex_unlock(&acpi_ioremap_lock);

- if (del)
- acpi_os_remove_map(map);
+ acpi_os_map_cleanup(map);
}

#ifdef ACPI_FUTURE_USAGE