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    SubjectRe: 2.6.18-rc5-mm1 + all hotfixes -- INFO: possible recursive locking detected
    On 9/6/06, Stefan Richter <stefanr@s5r6.in-berlin.de> 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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