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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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