Messages in this thread Patch in this message |  | | | Date | Thu, 22 Sep 2005 00:47:11 -0700 | | From | Greg KH <> | | Subject | [patch 01/18] Driver Core: fis bus rescan devices race |
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From: Daniel Ritz <daniel.ritz@gmx.ch>
bus_rescan_devices_helper() does not hold the dev->sem when it checks for !dev->driver(). device_attach() holds the sem, but calls again device_bind_driver() even when dev->driver is set.
What happens is that a first device_attach() call (module insertion time) is on the way binding the device to a driver. Another thread calls bus_rescan_devices(). Now when bus_rescan_devices_helper() checks for dev->driver it is still NULL 'cos the the prior device_attach() is not yet finished. But as soon as the first one releases the dev->sem the second device_attach() tries to rebind the already bound device again. device_bind_driver() does this blindly which leads to a corrupt driver->klist_devices list (the device links itself, the head points to the device). Later a call to device_release_driver() sets dev->driver to NULL and breaks the link it has to itself on knode_driver. Rmmoding the driver later calls driver_detach() which leads to an endless loop 'cos the list head in klist_devices still points to the device. And since dev->driver is NULL it's stuck with the same device forever. Boom. And rmmod hangs.
Very easy to reproduce with new-style pcmcia and a 16bit card. Just loop modprobe <pcmcia-modules> ;cardctl eject; rmmod <card driver, pcmcia modules>.
Easiest fix is to check if the device is already bound to a driver in device_bind_driver(). This avoids the double binding.
Signed-off-by: Daniel Ritz <daniel.ritz@gmx.ch> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/base/dd.c | 3 +++ 1 file changed, 3 insertions(+) --- scsi-2.6.orig/drivers/base/dd.c 2005-09-20 05:59:41.000000000 -0700 +++ scsi-2.6/drivers/base/dd.c 2005-09-21 17:29:03.000000000 -0700 @@ -40,6 +40,9 @@ */ void device_bind_driver(struct device * dev) { + if (klist_node_attached(&dev->knode_driver)) + return; + pr_debug("bound device '%s' to driver '%s'\n", dev->bus_id, dev->driver->name); klist_add_tail(&dev->knode_driver, &dev->driver->klist_devices); -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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