On 9/6/06, Stefan Richter <[email protected]> wrote:
I wrote:
> I wrote:
>> Or maybe it's older. Nodemgr takes class->subsys.rwsem and
>> device.bus->subsys.rwsem. It always did. Could there be a change in
>> driver core which makes this recursive? Or has it always been recursive?
>> For example,
>>
>> static void nodemgr_update_pdrv(struct node_entry *ne)
>> {
>> struct unit_directory *ud;
>> struct hpsb_protocol_driver *pdrv;
>> struct class *class = &nodemgr_ud_class;
>> struct class_device *cdev;
>>
>> down_read(&class->subsys.rwsem);
>> list_for_each_entry(cdev, &class->children, node) {
This may be wrong anyway. According to include/linux/device.h,
class->sem should be used to protect access to class->children. There
are more places in nodemgr of this sort.
>> ud = container_of(cdev, struct unit_directory, class_dev);
>> if (ud->ne != ne || !ud->device.driver)
>> continue;
>>
>> pdrv = container_of(ud->device.driver, struct hpsb_protocol_driver, driver);
>>
>> if (pdrv->update && pdrv->update(ud)) {
>> down_write(&ud->device.bus->subsys.rwsem);
>> device_release_driver(&ud->device);
>> up_write(&ud->device.bus->subsys.rwsem);
>> }
>> }
>> up_read(&class->subsys.rwsem);
>> }
>
> Hi Greg,
>
> perhaps you could advise on this. It appears from grepping through the
> sources that drivers/ieee1394/nodemgr.c is the only one with mixed
> access to device.bus->subsys.rwsem and class->subsys.rwsem.
>
> Other usages of subsys.rwsem that I found are:
> 1a.) dev->bus->subsys.rwsem
> driver/ide/ide-proc.c and drivers/net/phy/phy_device.c take
> dev->bus->subsys.rwsem. drivers/pnp/card.c takes dev.bus->subsys.rwsem.
>
> 1b.) driver.bus->subsys.rwsem
> drivers/s390/net/qeth_proc.c takes driver.bus->subsys.rwsem.
>
> 2.) class->subsys.rwsem
> drivers/scsi/hosts.c takes class->subsys.rwsem.
>
> 3.) bustype.subsys.rwsem
> drivers/input/serio/serio.c takes serio_bus.subsys.rwsem.
> drivers/input/gameport/gameport.c takes gameport_bus.subsys.rwsem.
> drivers/base/power/shutdown.c takes devices_subsys.rwsem.
> drivers/usb/core/devices.c and devio.c take usb_bus_type.subsys.rwsem.
>
> Do class->subsys.rwsem, bus->subsys.rwsem, and bus_type.subsys.rwsem
> point to identical or different lock instances?
>
> Either way, could it hurt to convert nodemgr to uniformly use
> ieee1394_bus_type.subsys.rwsem all over the place?
I don't have time to do the bisection testing. If there is a patch
you'd like me to test against 2.6.18-rc5-mm1+all hotfixes, please let
me know. I apologize for not being able to narrow this down further
for you.
Miles
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