I am working on the USB drivers trying to get the hub and the host
controller (uhci/ohci/ohci-hcd) drivers to unload correctly. The problem
is that the drivers have threads running that are not dying before I start
deallocating resources.
currently I am trying the following code (from hub.c):
=========begin code snip============
void cleanup_module(void)
{
if (khubd_pid >= 0)
{
int pid;
kill_proc(khubd_pid, SIGTERM, 1);
pid=waitpid(khubd_pid, NULL, __WCHILD);
if (pid!=khubd_pid)
printk("waitpid filed,"
"khubd_pid=%i,retpid=%i\n",khubd_pid,pid);
}
usb_deregister(&hub_driver);
}
=========end code snip============
Sometimes it works. Othertimes I get the waitpid filed (ok, so I typed
'failed' wrong...) message, promptly followed by a kernel oops.
The thread is created as follows...
=========begin code snip============
pid = kernel_thread(usb_hub_thread, NULL, CLONE_FS | CLONE_FILES |
CLONE_FILES | CLONE_SIGHAND);
if (pid >= 0) {
khubd_pid = pid;
return 0;
}
/* Fall through if kernel_thread failed */
--with the actual start of usb_hub_thread looking like
static int usb_hub_thread(void *__hub){
lock_kernel();
/*
static int usb_hub_thread(void *__hub){
lock_kernel();
/*
* This thread doesn't need any user-level access,
* so get rid of all our resources
*/
printk("usb_hub_thread at %p\n", &usb_hub_thread);
exit_mm(current);
exit_files(current);
exit_fs(current);
=========end code snip============
Anyways, my question is.. obviously my method of killing and then waiting
for the process to die is not working right. What can I do instead? Wait
queues do not seem to satisfy my needs, and I'm hesitant to look at
putting a 50 ms sleep in or something of the like.
can I just do a
while (wait_pid(pid,NULL,__WCLONE)==-1){wait_ms(10)};
and hope that eventually it exits?
-David Waite
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