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):
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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