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


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