On Mon, Nov 06, 2017 at 06:03:08PM +0800, Chen Yu wrote: > Hi, > > On 2017/11/6 16:31, Greg KH wrote: > > On Mon, Nov 06, 2017 at 04:20:23PM +0800, Yu Chen wrote: > >> From: Yu Chen <chenyu56@xxxxxxxxxx> > >> > >> Check vdev->real_port 0 to avoid panic > >> [ 9.261347] [<ffffff800884a390>] xhci_free_virt_devices_depth_first+0x58/0x108 > >> [ 9.261352] [<ffffff800884a814>] xhci_mem_cleanup+0x1bc/0x570 > >> [ 9.261355] [<ffffff8008842de8>] xhci_stop+0x140/0x1c8 > >> [ 9.261365] [<ffffff80087ed304>] usb_remove_hcd+0xfc/0x1d0 > >> [ 9.261369] [<ffffff80088551c4>] xhci_plat_remove+0x6c/0xa8 > >> [ 9.261377] [<ffffff80086e928c>] platform_drv_remove+0x2c/0x70 > >> [ 9.261384] [<ffffff80086e6ea0>] __device_release_driver+0x80/0x108 > >> [ 9.261387] [<ffffff80086e7a1c>] device_release_driver+0x2c/0x40 > >> [ 9.261392] [<ffffff80086e5f28>] bus_remove_device+0xe0/0x120 > >> [ 9.261396] [<ffffff80086e2e34>] device_del+0x114/0x210 > >> [ 9.261399] [<ffffff80086e9e00>] platform_device_del+0x30/0xa0 > >> [ 9.261403] [<ffffff8008810bdc>] dwc3_otg_work+0x204/0x488 > >> [ 9.261407] [<ffffff80088133fc>] event_work+0x304/0x5b8 > >> [ 9.261414] [<ffffff80080e31b0>] process_one_work+0x148/0x490 > >> [ 9.261417] [<ffffff80080e3548>] worker_thread+0x50/0x4a0 > >> [ 9.261421] [<ffffff80080e9ea0>] kthread+0xe8/0x100 > >> [ 9.261427] [<ffffff8008083680>] ret_from_fork+0x10/0x50 > >> > >> The problem can occur if xhci_plat_remove() is called shortly after > >> xhci_plat_probe(). While xhci_free_virt_devices_depth_first been > >> called before the device has been setup and get real_port initialized. > >> The problem occurred on Hikey960 and was reproduced by Guenter Roeck > >> on Kevin with chromeos-4.4. > >> > >> Cc: Guenter Roeck <groeck@xxxxxxxxxx> > >> Signed-off-by: Fan Ning <fanning4@xxxxxxxxxxxxx> > >> Signed-off-by: Li Rui <lirui39@xxxxxxxxxxxxx> > >> Signed-off-by: yangdi <yangdi10@xxxxxxxxxxxxx> > >> Signed-off-by: Yu Chen <chenyu56@xxxxxxxxxx> > >> > >> --- > >> drivers/usb/host/xhci-mem.c | 4 ++++ > >> 1 file changed, 4 insertions(+) > >> > >> diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c > >> index 2a82c927ded2..0361b4a58f59 100644 > >> --- a/drivers/usb/host/xhci-mem.c > >> +++ b/drivers/usb/host/xhci-mem.c > >> @@ -947,6 +947,9 @@ void xhci_free_virt_devices_depth_first(struct xhci_hcd *xhci, int slot_id) > >> if (!vdev) > >> return; > >> > >> + if (WARN_ON(!vdev->real_port)) > > > > Ok, now you are sending a lot of mess to the kernel log, so what can a > > user do about it? > > > > How can this ever happen? Is it a hardware error, or a kernel driver > > logic error? > > > > thanks, > > > > greg k-h > > > > . > > > > The problem is a driver logic error, it can reproduced if xhci_plat_remove() is > called shortly after xhci_plat_probe() while xhci_alloc_virt_device has been called > but real_port has not been initialized in xhci_setup_addressable_virt_dev. Who is calling xhci_plat_remove() like this? > A simple process is as below: > xhci_plat_probe() > | > usb_add_hcd() xhci_plat_remove() > | | > find some device usb_remove_hcd() > | | > hub_port_connect() -> usb_alloc_dev() usb_disconnect() > | | > before hub_enable_device() xhci_stop() > | > xhci_mem_cleanup() > | > xhci_free_virt_devices_depth_first() > | > real_port is 0 access xhci->rh_bw[vdev->real_port-1] > > The problem came from https://bugs.96boards.org/show_bug.cgi?id=535 > Also look at crbug.com/700041 Then the bug needs to be fixed, throwing a huge kernel trace message into the kernel log is not "fixing" the problem at all, right? thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
