While stress testing a usb controller using a bind/unbind looop, the following error loop was observed. usb 7-1.2: new low-speed USB device number 3 using xhci-hcd usb 7-1.2: hub failed to enable device, error -108 usb 7-1-port2: cannot disable (err = -22) usb 7-1-port2: couldn't allocate usb_device usb 7-1-port2: cannot disable (err = -22) hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: activate --> -22 hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: activate --> -22 hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: activate --> -22 hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: activate --> -22 hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: activate --> -22 hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: activate --> -22 hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: activate --> -22 hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: activate --> -22 hub 7-1:1.0: hub_ext_port_status failed (err = -22) hub 7-1:1.0: hub_ext_port_status failed (err = -22) ** 57 printk messages dropped ** hub 7-1:1.0: activate --> -22 ** 82 printk messages dropped ** hub 7-1:1.0: hub_ext_port_status failed (err = -22) This continues forever. After adding tracebacks into the code, the call sequence leading to this is found to be as follows. [<ffffffc0007fc8e0>] hub_activate+0x368/0x7b8 [<ffffffc0007fceb4>] hub_resume+0x2c/0x3c [<ffffffc00080b3b8>] usb_resume_interface.isra.6+0x128/0x158 [<ffffffc00080b5d0>] usb_suspend_both+0x1e8/0x288 [<ffffffc00080c9c4>] usb_runtime_suspend+0x3c/0x98 [<ffffffc0007820a0>] __rpm_callback+0x48/0x7c [<ffffffc00078217c>] rpm_callback+0xa8/0xd4 [<ffffffc000786234>] rpm_suspend+0x84/0x758 [<ffffffc000786ca4>] rpm_idle+0x2c8/0x498 [<ffffffc000786ed4>] __pm_runtime_idle+0x60/0xac [<ffffffc00080eba8>] usb_autopm_put_interface+0x6c/0x7c [<ffffffc000803798>] hub_event+0x10ac/0x12ac [<ffffffc000249bb8>] process_one_work+0x390/0x6b8 [<ffffffc00024abcc>] worker_thread+0x480/0x610 [<ffffffc000251a80>] kthread+0x164/0x178 [<ffffffc0002045d0>] ret_from_fork+0x10/0x40 kick_hub_wq() is called from hub_activate() even after failures to communicate with the hub. This results in an endless sequence of hub event -> hub activate -> wq trigger -> hub event -> ... To break the loop, only trigger the hub event queue if communication with the hub is successful. Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx> --- drivers/usb/core/hub.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 5286bf67869a..f22ab428b310 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -1197,7 +1197,8 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type) &hub->leds, LED_CYCLE_PERIOD); /* Scan all ports that need attention */ - kick_hub_wq(hub); + if (!status) + kick_hub_wq(hub); if (type == HUB_INIT2 || type == HUB_INIT3) { /* Allow autosuspend if it was suppressed */ -- 2.7.4 -- 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