Date: Wed, 22 Nov 2006 21:09:42 +0100 From: Stefan Richter Subject: ieee1394: nodemgr: fix deadlock in shutdown If "modprobe ohci1394" was quickly followed by "modprobe -r ohci1394", say with 1 second pause in between, the modprobe -r got stuck in uninterruptible sleep in kthread_stop. At the same time the knodemgrd slept uninterruptibly in bus_rescan_devices_helper. That's because driver_detach took the semaphore of the PCI device and bus_rescan_devices_helper wanted to take the semaphore of the FireWire host device's parent, which is the same semaphore. This was a regression since Linux 2.6.16, commit bf74ad5bc41727d5f2f1c6bedb2c1fac394de731, "Hold the device's parent's lock during probe and remove". The fix (or workaround) adds a dummy driver to the hpsb_host device. Now bus_rescan_devices_helper won't scan the host device anymore. This doesn't hurt since we have no drivers which will bind to these devices and it is unlikely that there will ever be such a driver. The dummy driver is befittingly presented as a representation of ieee1394 itself. Fixes: http://bugzilla.kernel.org/show_bug.cgi?id=6706 Signed-off-by: Stefan Richter --- drivers/ieee1394/nodemgr.c | 21 ++++++++++++++++++--- 1 files changed, 18 insertions(+), 3 deletions(-) Index: linux/drivers/ieee1394/nodemgr.c =================================================================== --- linux.orig/drivers/ieee1394/nodemgr.c 2006-11-21 00:09:25.000000000 +0100 +++ linux/drivers/ieee1394/nodemgr.c 2006-11-21 22:32:09.000000000 +0100 @@ -14,6 +14,7 @@ #include #include #include +#include #include #include @@ -259,9 +260,20 @@ static struct device nodemgr_dev_templat .release = nodemgr_release_ne, }; +/* This dummy driver prevents the host devices from being scanned. We have no + * useful drivers for them yet, and there would be a deadlock possible if the + * driver core scans the host device while the host's low-level driver (i.e. + * the host's parent device) is being removed. */ +static struct device_driver nodemgr_mid_layer_driver = { + .bus = &ieee1394_bus_type, + .name = "nodemgr", + .owner = THIS_MODULE, +}; + struct device nodemgr_dev_template_host = { .bus = &ieee1394_bus_type, .release = nodemgr_release_host, + .driver = &nodemgr_mid_layer_driver, }; @@ -704,11 +716,14 @@ static int nodemgr_bus_match(struct devi return 0; ud = container_of(dev, struct unit_directory, device); - driver = container_of(drv, struct hpsb_protocol_driver, driver); - if (ud->ne->in_limbo || ud->ignore_driver) return 0; + /* We only match drivers of type hpsb_protocol_driver */ + if (drv == &nodemgr_mid_layer_driver) + return 0; + + driver = container_of(drv, struct hpsb_protocol_driver, driver); for (id = driver->id_table; id->match_flags != 0; id++) { if ((id->match_flags & IEEE1394_MATCH_VENDOR_ID) && id->vendor_id != ud->vendor_id) @@ -1899,7 +1914,7 @@ int init_ieee1394_nodemgr(void) class_unregister(&nodemgr_ne_class); return error; } - + error = driver_register(&nodemgr_mid_layer_driver); hpsb_register_highlevel(&nodemgr_highlevel); return 0; }