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    SubjectRe: [PATCH 2.6.10-rc1 2/5] driver-model: bus_recan_devices() locking fix
     df_02_bus_rescan_devcies_fix.patch

    bus_rescan_devices() eventually calls device_attach() and thus
    requires write locking the corresponding bus. The original code just
    called bus_for_each_dev() which only read locks the bus. This patch
    separates __bus_for_each_dev() and __bus_for_each_drv(), which don't
    do locking themselves, out from the original functions and call them
    with read lock in the original functions and with write lock in
    bus_rescan_devices().


    Signed-off-by: Tejun Heo <tj@home-tj.org>


    Index: linux-export/drivers/base/bus.c
    ===================================================================
    --- linux-export.orig/drivers/base/bus.c 2004-11-04 11:04:13.000000000 +0900
    +++ linux-export/drivers/base/bus.c 2004-11-04 11:04:13.000000000 +0900
    @@ -135,6 +135,54 @@ static struct kobj_type ktype_bus = {

    decl_subsys(bus, &ktype_bus, NULL);

    +static int
    +__bus_for_each_dev(struct bus_type * bus, struct device * start,
    + void * data, int (*fn)(struct device *, void *))
    +{
    + struct device *dev;
    + struct list_head * head;
    + int error = 0;
    +
    + if (!(bus = get_bus(bus)))
    + return -EINVAL;
    +
    + head = &bus->devices.list;
    + dev = list_prepare_entry(start, head, bus_list);
    + list_for_each_entry_continue(dev, head, bus_list) {
    + get_device(dev);
    + error = fn(dev, data);
    + put_device(dev);
    + if (error)
    + break;
    + }
    + put_bus(bus);
    + return error;
    +}
    +
    +static int
    +__bus_for_each_drv(struct bus_type * bus, struct device_driver * start,
    + void * data, int (*fn)(struct device_driver *, void *))
    +{
    + struct list_head * head;
    + struct device_driver *drv;
    + int error = 0;
    +
    + if(!(bus = get_bus(bus)))
    + return -EINVAL;
    +
    + head = &bus->drivers.list;
    + drv = list_prepare_entry(start, head, kobj.entry);
    + list_for_each_entry_continue(drv, head, kobj.entry) {
    + get_driver(drv);
    + error = fn(drv, data);
    + put_driver(drv);
    + if(error)
    + break;
    + }
    + put_bus(bus);
    + return error;
    +}
    +
    /**
    * bus_for_each_dev - device iterator.
    * @bus: bus type.
    @@ -154,30 +202,15 @@ decl_subsys(bus, &ktype_bus, NULL);
    * to retain this data, it should do, and increment the reference
    * count in the supplied callback.
    */
    +
    int bus_for_each_dev(struct bus_type * bus, struct device * start,
    void * data, int (*fn)(struct device *, void *))
    {
    - struct device *dev;
    - struct list_head * head;
    - int error = 0;
    -
    - if (!(bus = get_bus(bus)))
    - return -EINVAL;
    -
    - head = &bus->devices.list;
    - dev = list_prepare_entry(start, head, bus_list);
    -
    + int ret;
    down_read(&bus->subsys.rwsem);
    - list_for_each_entry_continue(dev, head, bus_list) {
    - get_device(dev);
    - error = fn(dev, data);
    - put_device(dev);
    - if (error)
    - break;
    - }
    + ret = __bus_for_each_dev(bus, start, data, fn);
    up_read(&bus->subsys.rwsem);
    - put_bus(bus);
    - return error;
    + return ret;
    }

    /**
    @@ -203,27 +236,11 @@ int bus_for_each_dev(struct bus_type * b
    int bus_for_each_drv(struct bus_type * bus, struct device_driver * start,
    void * data, int (*fn)(struct device_driver *, void *))
    {
    - struct list_head * head;
    - struct device_driver *drv;
    - int error = 0;
    -
    - if(!(bus = get_bus(bus)))
    - return -EINVAL;
    -
    - head = &bus->drivers.list;
    - drv = list_prepare_entry(start, head, kobj.entry);
    -
    + int ret;
    down_read(&bus->subsys.rwsem);
    - list_for_each_entry_continue(drv, head, kobj.entry) {
    - get_driver(drv);
    - error = fn(drv, data);
    - put_driver(drv);
    - if(error)
    - break;
    - }
    + ret = __bus_for_each_drv(bus, start, data, fn);
    up_read(&bus->subsys.rwsem);
    - put_bus(bus);
    - return error;
    + return ret;
    }

    /**
    @@ -601,7 +618,9 @@ int bus_rescan_devices(struct bus_type *
    {
    int count = 0;

    - bus_for_each_dev(bus, NULL, &count, bus_rescan_devices_helper);
    + down_write(&bus->subsys.rwsem);
    + __bus_for_each_dev(bus, NULL, &count, bus_rescan_devices_helper);
    + up_write(&bus->subsys.rwsem);

    return count;
    }
    -
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