usbcore: Limit number of 'unable to enumerate USB device' messages
PATCH 1/1 usbcore: Limit number of 'unable to enumerate USB device' messages
In my system, a number of messages that state "unable to enumerate USB device" are logged. These are intermittent and likely due to some race condition at bootup.
Some of these happen when the EHCI driver is loaded after UHCI or OHCI, which causes the device to be switched away from the other controller that's trying to enumerate it, at least momentarily. This type of message is logged at most once for each hub and occurs in about 70% of my reboots.
A more insidious form of the message occurs hundreds of times in about 10% of reboots. They continue until the system is rebooted. This patch limits the number of these messages to 20. Once the actual cause of this message is located, this patch can be reverted.
---
drivers/usb/core/hub.c +4 -2
@@ -2746,6 +2746,7 @@ static void hub_port_connect_change(strule16_to_cpu (hub->descriptor->wHubCharacteristics);struct usb_device *udev;int status, i; +static int enum_count; dev_dbg (hub_dev, "port %d, status %04x, change %04x, %s\n",
@@ -2945,8 +2946,9 @@ loop:if (hub->hdev->parent || !hcd->driver->port_handed_over || !(hcd->driver->port_handed_over)(hcd, port1)) -dev_err (hub_dev,"unable to enumerate USB device on port %d\n" , - port1); +if (enum_count++ <20 ) +dev_err (hub_dev,"unable to enumerate USB device on " +"port %d\n" , port1); done:hub_port_disable (hub, port1,1 );
Quoted 8 lines · Larry Finger
In my system, a number of messages that state "unable to enumerate USB device" are logged. These are intermittent and likely due to some race condition at bootup.
Some of these happen when the EHCI driver is loaded after UHCI or OHCI, which causes the device to be switched away from the other controller that's trying to enumerate it, at least momentarily. This type of message is logged at most once for each hub and occurs in about 70% of my reboots.
What kernel version are you having these problems with?
thanks,
greg k-h
Quoted 1 line · Greg KH
What kernel version are you having these problems with?
This problem started sometime in the 2.6.26-git sequence, and persists to the latest from the linux-2.6 git tree.
Larry
Quoted 6 lines · Larry Finger
Quoted 1 line · Greg KH
What kernel version are you having these problems with?
This problem started sometime in the 2.6.26-git sequence, and persists to the latest from the linux-2.6 git tree.
The latest tree should warn you if you load the host controller drivers in the wrong order, so this shouldn't really be an issue anymore, right?
Like Alan said, proper log messages would be helpful here.
thanks,
greg k-h
Quoted 3 lines · Greg KH
The latest tree should warn you if you load the host controller drivers in the wrong order, so this shouldn't really be an issue anymore, right?
I have not seen such warhings, thus I expect loading is in the proper order.
Quoted 2 lines
Like Alan said, proper log messages would be helpful here.
Agreed, but I have no idea what I should be looking for. For the moment, I have lots of test prints looking for the sequence of events that lead to this spamming of the logs.
Larry
Quoted 5 lines · Larry Finger
Quoted 3 lines · Greg KH
The latest tree should warn you if you load the host controller drivers in the wrong order, so this shouldn't really be an issue anymore, right?
Quoted 7 lines
I have not seen such warhings, thus I expect loading is in the proper order.
Quoted 2 lines
Like Alan said, proper log messages would be helpful here.
Agreed, but I have no idea what I should be looking for. For the moment, I have lots of test prints looking for the sequence of events that lead to this spamming of the logs.
Just build your test kernel with USB debugging enabled, and when you get that spamming, post the complete dmesg log.
Alan Stern
Quoted 3 lines · Alan Stern
Just build your test kernel with USB debugging enabled, and when you get that spamming, post the complete dmesg log.
Once I added ehci_hcd to my initrd, which ensured that it was loaded first, the error messages seem to have disappeared. If they return, I'll open a new thread.
Thanks for the help,
Larry
Quoted 8 lines · Larry Finger
In my system, a number of messages that state "unable to enumerate USB device" are logged. These are intermittent and likely due to some race condition at bootup.
Some of these happen when the EHCI driver is loaded after UHCI or OHCI, which causes the device to be switched away from the other controller that's trying to enumerate it, at least momentarily. This type of message is logged at most once for each hub and occurs in about 70% of my reboots.
This is normal; it is caused by userspace loading the drivers in the wrong order. ehci-hcd is supposed to be loaded before uhci-hcd or ohci-hcd, not after. There's no point trying to change the kernel to avoid it.
Quoted 4 lines
A more insidious form of the message occurs hundreds of times in about 10% of reboots. They continue until the system is rebooted. This patch limits the number of these messages to 20. Once the actual cause of this message is located, this patch can be reverted.
I would prefer to attack this problem directly rather than wallpaper over it. Can you provide more information? For example, a dmesg log with CONFIG_USB_DEBUG and CONFIG_PRINTK_TIME enabled would help. It might also help to know what the devices which can't be enumerated actually are.
Alan Stern