Re: [linux-usb-devel] init 1 kill khubd on 2.6.11

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On Monday 02 May 2005 02:30, Andrew Morton wrote:
> Alan Stern <[email protected]> wrote:
> > On Sun, 1 May 2005, Andrey Borzenkov wrote:
> > > Hub driver is using SIGKILL to terminate khubd. Unfortunately on a
> > > number of distributions switching init levels implicitly does "killall
> > > -9", killing khubd. The only way to restart it is to reload USB
> > > subsystem.
> > >
> > > Is signal usage in this case really needed? What about replacing it
> > > with simple flag (i.e. will patch be accepted)?
> >
> > IMO the problem lies in those distributions.  They should not
> > indiscrimately kill processes when switching init levels.
>
> Nevertheless it's better that kernel internals not be exposed to userspace
> actions in this manner, and using signals for in-kernel IPC is crufty, IMO.
>
> It's pretty simple to convert khubd to use the kthread API.  Something like
> this (untested):
>


Something strange is going on with this patch.

insmod usbcore; insmod uhci-hcd works as expected, finds out all devices, 
triggers hotplug etc. But

{pts/2}% sudo insmod ./usbcore.ko
{pts/2}% sudo mount -t usbfs -o devmode=0664,devgid=43 none /proc/bus/usb
{pts/2}% sudo modprobe usb-interface

results in

usbcore: registered new driver usbfs
usbcore: registered new driver hub
USB Universal Host Controller Interface driver v2.2
ACPI: PCI interrupt 0000:00:1f.2[D] -> GSI 5 (level, low) -> IRQ 5
uhci_hcd 0000:00:1f.2: UHCI Host Controller
PCI: Setting latency timer of device 0000:00:1f.2 to 64
uhci_hcd 0000:00:1f.2: irq 5, io base 0xa400
uhci_hcd 0000:00:1f.2: new USB bus registered, assigned bus number 1
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 2 ports detected
ACPI: PCI interrupt 0000:00:1f.4[C] -> GSI 9 (level, low) -> IRQ 9
uhci_hcd 0000:00:1f.4: UHCI Host Controller
PCI: Setting latency timer of device 0000:00:1f.4 to 64
uhci_hcd 0000:00:1f.4: irq 9, io base 0xa000
usb 1-1: new low speed USB device using uhci_hcd and address 2
uhci_hcd 0000:00:1f.2: Unlink after no-IRQ?  Controller is probably using the 
wrong IRQ.
usb 1-1: khubd timed out on ep0out
usb 1-1: khubd timed out on ep0out
usb 1-1: device not accepting address 2, error -110
usb 1-1: new low speed USB device using uhci_hcd and address 3
usb 1-1: khubd timed out on ep0out
usb 1-1: khubd timed out on ep0out
usb 1-1: device not accepting address 3, error -110
usb 1-1: new low speed USB device using uhci_hcd and address 4
usb 1-1: khubd timed out on ep0in
usb 1-1: khubd timed out on ep0out
usb 1-1: khubd timed out on ep0out
usb 1-1: device not accepting address 4, error -110
usb 1-1: new low speed USB device using uhci_hcd and address 5
usb 1-1: khubd timed out on ep0in
usb 1-1: khubd timed out on ep0out
usb 1-1: khubd timed out on ep0out
usb 1-1: device not accepting address 5, error -110
usb 1-2: new full speed USB device using uhci_hcd and address 6
usb 1-2: khubd timed out on ep0out
usb 1-2: khubd timed out on ep0out
usb 1-2: device not accepting address 6, error -110
usb 1-2: new full speed USB device using uhci_hcd and address 7
usb 1-2: khubd timed out on ep0out
usb 1-2: khubd timed out on ep0out
usb 1-2: device not accepting address 7, error -110
usb 1-2: new full speed USB device using uhci_hcd and address 8
usb 1-2: khubd timed out on ep0in
usb 1-2: khubd timed out on ep0out
usb 1-2: khubd timed out on ep0out
usb 1-2: device not accepting address 8, error -110
usb 1-2: new full speed USB device using uhci_hcd and address 9
usb 1-2: khubd timed out on ep0in
usb 1-2: khubd timed out on ep0out
usb 1-2: khubd timed out on ep0out
usb 1-2: device not accepting address 9, error -110
uhci_hcd 0000:00:1f.4: new USB bus registered, assigned bus number 2
hub 2-0:1.0: USB hub found
hub 2-0:1.0: 2 ports detected
usb 2-2: new full speed USB device using uhci_hcd and address 2
hub 2-2:1.0: USB hub found
hub 2-2:1.0: 4 ports detected

I do not understand what difference mounting usbfs makes. For reference here 
is result of loading the same usbcore without mounting usbfs:

{pts/2}% sudo insmod ./usbcore-new.ko
{pts/2}% sudo modprobe uhci-hcd

usbcore: registered new driver usbfs
usbcore: registered new driver hub
USB Universal Host Controller Interface driver v2.2
ACPI: PCI interrupt 0000:00:1f.2[D] -> GSI 5 (level, low) -> IRQ 5
uhci_hcd 0000:00:1f.2: UHCI Host Controller
PCI: Setting latency timer of device 0000:00:1f.2 to 64
uhci_hcd 0000:00:1f.2: irq 5, io base 0xa400
uhci_hcd 0000:00:1f.2: new USB bus registered, assigned bus number 1
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 2 ports detected
ACPI: PCI interrupt 0000:00:1f.4[C] -> GSI 9 (level, low) -> IRQ 9
uhci_hcd 0000:00:1f.4: UHCI Host Controller
PCI: Setting latency timer of device 0000:00:1f.4 to 64
uhci_hcd 0000:00:1f.4: irq 9, io base 0xa000
uhci_hcd 0000:00:1f.4: new USB bus registered, assigned bus number 2
hub 2-0:1.0: USB hub found
hub 2-0:1.0: 2 ports detected
usb 1-1: new low speed USB device using uhci_hcd and address 2
usb 1-2: new full speed USB device using uhci_hcd and address 3
usb 2-2: new full speed USB device using uhci_hcd and address 2
hub 2-2:1.0: USB hub found
hub 2-2:1.0: 4 ports detected
drivers/usb/class/usblp.c: usblp0: USB Bidirectional printer dev 3 if 0 alt 0 
proto 2 vid 0x03F0 pid 0x1904
usbcore: registered new driver usblp
drivers/usb/class/usblp.c: v0.13: USB Printer Device Class driver
usbcore: registered new driver hiddev
usbhid: probe of 1-1:1.0 failed with error -5
usbcore: registered new driver usbhid
drivers/usb/input/hid-core.c: v2.0:USB HID core driver
usbcore: registered new driver xpad
drivers/usb/input/xpad-core.c: driver for Xbox controllers with mouse 
emulation v0.1.4


-andrey

>  drivers/usb/core/hub.c |   40 +++++++++++-----------------------------
>  1 files changed, 11 insertions(+), 29 deletions(-)
>
> diff -puN drivers/usb/core/hub.c~hub-use-kthread drivers/usb/core/hub.c
> --- 25/drivers/usb/core/hub.c~hub-use-kthread	2005-05-01 15:22:24.634539928
> -0700 +++ 25-akpm/drivers/usb/core/hub.c	2005-05-01 15:29:55.739961480
> -0700 @@ -26,6 +26,7 @@
>  #include <linux/ioctl.h>
>  #include <linux/usb.h>
>  #include <linux/usbdevice_fs.h>
> +#include <linux/kthread.h>
>
>  #include <asm/semaphore.h>
>  #include <asm/uaccess.h>
> @@ -47,8 +48,7 @@ static LIST_HEAD(hub_event_list);	/* Lis
>  /* Wakes up khubd */
>  static DECLARE_WAIT_QUEUE_HEAD(khubd_wait);
>
> -static pid_t khubd_pid = 0;			/* PID of khubd */
> -static DECLARE_COMPLETION(khubd_exited);
> +static struct task_struct *khubd_task;
>
>  /* cycle leds on hubs that aren't blinking for attention */
>  static int blinkenlights = 0;
> @@ -2807,23 +2807,16 @@ loop:
>
>  static int hub_thread(void *__unused)
>  {
> -	/*
> -	 * This thread doesn't need any user-level access,
> -	 * so get rid of all our resources
> -	 */
> -
> -	daemonize("khubd");
> -	allow_signal(SIGKILL);
> -
> -	/* Send me a signal to get me die (for debugging) */
>  	do {
>  		hub_events();
> -		wait_event_interruptible(khubd_wait, !list_empty(&hub_event_list));
> +		wait_event_interruptible(khubd_wait,
> +				!list_empty(&hub_event_list) ||
> +				kthread_should_stop());
>  		try_to_freeze(PF_FREEZE);
> -	} while (!signal_pending(current));
> +	} while (!kthread_should_stop() || !list_empty(&hub_event_list));
>
> -	pr_debug ("%s: khubd exiting\n", usbcore_name);
> -	complete_and_exit(&khubd_exited, 0);
> +	pr_debug("%s: khubd exiting\n", usbcore_name);
> +	return 0;
>  }
>
>  static struct usb_device_id hub_id_table [] = {
> @@ -2849,20 +2842,15 @@ static struct usb_driver hub_driver = {
>
>  int usb_hub_init(void)
>  {
> -	pid_t pid;
> -
>  	if (usb_register(&hub_driver) < 0) {
>  		printk(KERN_ERR "%s: can't register hub driver\n",
>  			usbcore_name);
>  		return -1;
>  	}
>
> -	pid = kernel_thread(hub_thread, NULL, CLONE_KERNEL);
> -	if (pid >= 0) {
> -		khubd_pid = pid;
> -
> +	khubd_task = kthread_run(hub_thread, NULL, "khubd");
> +	if (!IS_ERR(khubd_task))
>  		return 0;
> -	}
>
>  	/* Fall through if kernel_thread failed */
>  	usb_deregister(&hub_driver);
> @@ -2873,12 +2861,7 @@ int usb_hub_init(void)
>
>  void usb_hub_cleanup(void)
>  {
> -	int ret;
> -
> -	/* Kill the thread */
> -	ret = kill_proc(khubd_pid, SIGKILL, 1);
> -
> -	wait_for_completion(&khubd_exited);
> +	kthread_stop(khubd_task);
>
>  	/*
>  	 * Hub resources are freed for us by usb_deregister. It calls
> @@ -2890,7 +2873,6 @@ void usb_hub_cleanup(void)
>  	usb_deregister(&hub_driver);
>  } /* usb_hub_cleanup() */
>
> -
>  static int config_descriptors_changed(struct usb_device *udev)
>  {
>  	unsigned			index;
> _

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