Hi ...
>> I have created a small linux kernel module in Ubuntu 6.06 which has
> >'init_module()' but no 'cleanup_module()'.
>>
<snip>
>> I loaded this module using the command 'sudo insmod start.ko'. But
> >when I try to remove 'start' from the kernel, I get this error
> >message.
>
> >$ sudo insmod start.ko
> >$ sudo rmmod start.ko
> >ERROR: Removing 'start': Device or resource busy
>take a look on kernel/module.c in your kernel source (2.6.x) Around line
>685, you'll see something like these:
/* If it has an init func, it must have an exit func to unload */
if ((mod->init != NULL && mod->exit == NULL)
|| mod->unsafe) {
forced = try_force_unload(flags);
if (!forced) {
/* This module can't be removed */
ret = -EBUSY;
goto out;
}
}
>Short story, the first "if" yields "true" result in your case, since
>exit function isn't declared (thus it's NULL). It then goes to do
>try_force_unload, but again it fails :
static inline int try_force_unload(unsigned int flags)
{
int ret = (flags & O_TRUNC);
if (ret)
add_taint(TAINT_FORCED_RMMOD);
return ret;
}
>I have no idea what O_TRUNC is, but certainly in your case this flag is
>off so "forced" contains "false". In the end, you hit the "ret=-EBUSY"
>line and in user space you see the message "resource busy".
The explaination is good, but one point was missed here..
Here in "try_force_unload()" flags is "FALSE" because, you had not passed
any parameters to "rmmod".
So, to make the flags "TRUE", try with following command:
]#rmmod -f strat.ko
Here by giving options "-f" the flags will be "TRUE" and then the
module will be removed.
For more details, see man page of "rmmod".
Regards,
Madhukar Mythri.
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