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authorJiri Slaby <jslaby@suse.cz>2014-11-21 10:05:09 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-11-26 19:33:57 -0800
commit91905b6f4afe51e23a3f58df93e4cdc5e49cf40c (patch)
tree941d6719f527d038e9daaf37686a27fb825223cd /Documentation/ABI
parent5b48e0605a84c3d2ccd06f6218df90e737c10559 (diff)
parport: parport_pc, do not remove parent devices early
When the parport_pc module is removed from the system, all parport devices are iterated in parport_pc_exit and removed by a call to parport_pc_unregister_port. Note that some parport devices have its 'struct device' parent, known as port->dev. And when port->dev is a platform device, it is destroyed in parport_pc_exit too. Now, when parport_pc_unregister_port is called for a going port, drv->detach(port) is called for every parport driver in the system. ppdev can be one of them. ppdev's detach() tears down its per-port sysfs directory, which established port->dev as a parent earlier. But since parport_pc_exit kills port->dev parents before unregisters ports proper, ppdev's sysfs directory has no living parent anymore. This results in the following warning: WARNING: CPU: 1 PID: 785 at fs/sysfs/group.c:219 sysfs_remove_group+0x9b/0xa0 sysfs group ffffffff81c69e20 not found for kobject 'parport1' Modules linked in: parport_pc(E-) ppdev(E) [last unloaded: ppdev] CPU: 1 PID: 785 Comm: rmmod Tainted: G W E 3.18.0-rc5-next-20141120+ #824 ... Call Trace: ... [<ffffffff810aff76>] warn_slowpath_fmt+0x46/0x50 [<ffffffff8123d81b>] sysfs_remove_group+0x9b/0xa0 [<ffffffff814c27e7>] dpm_sysfs_remove+0x57/0x60 [<ffffffff814b6ac9>] device_del+0x49/0x240 [<ffffffff814b6ce2>] device_unregister+0x22/0x70 [<ffffffff814b6dac>] device_destroy+0x3c/0x50 [<ffffffffc012209a>] pp_detach+0x4a/0x60 [ppdev] [<ffffffff814b32dd>] parport_remove_port+0x11d/0x150 [<ffffffffc0137328>] parport_pc_unregister_port+0x28/0xf0 [parport_pc] [<ffffffffc0138c0e>] parport_pc_exit+0x76/0x468 [parport_pc] [<ffffffff81128dbc>] SyS_delete_module+0x18c/0x230 It is also easily reproducible on qemu with two dummy ports '-parallel /dev/null -parallel /dev/null'. So switch the order of killing the two structures. But since port is freed by parport_pc_unregister_port, we have to remember port->dev in a local variable. Perhaps nothing worse than the warning happens thanks to the device refcounting. We *should* be on the safe side. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Reviewed-by: Takashi Iwai <tiwai@suse.de> Tested-by: Martin Pluskal <mpluskal@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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