Re: Stopping Kernel Threads at module unload time

[linux-os (Dick Johnson)]

On Wed, 9 Nov 2005, Aritz Bastida wrote:

>>
>>> Now, if I call kthread_stop() in module unload time, does that code
>>> run in user process context just like system calls do? That is
>>> important, because if it cannot sleep, it would deadlock.
>>>
>>
>> Not relevent. You have apparently made up your mind that you
>> need to do it "your" way. Fine.
>
> No, no, that is not MY way. That is the 2.6 way.
> (see http://lwn.net/Articles/64444/).
>
> With the old API (kernel_thread) there was no way (at least, direct
> way) to bind a thread to a cpu, which i actually need. And this is not
> MY own approach , it is used throught the kernel:
>
> * migration thread at sched.c:
>           http://lxr.linux.no/source/kernel/sched.c#L4196
>
> * ksoftirqd thread at softirq.c:
>           http://lxr.linux.no/source/kernel/softirq.c#L350
>
> * worker thread used in workqueues:
>           http://lxr.linux.no/source/kernel/workqueue.c#L182
>
> ...and so on
>
> All these threads are standard and well debugged, and all use the API
> which I was talking about. Of course, as they are included in the
> official kernel sources, none of them is stopped at module unload
> time.
>
> Thus, all I want to know is why kthread_stop() cant be called at
> module unload time, if the cleanup code can sleep and if there is a
> workaround for that.
>
> I hope my questions are clearer now.
> Thanks for your help

Then if you are going to use the macros to bind to a certain CPU
when you start up a kernel thread, then you need to use the
complimenting macros to run them down.

You need to use the for_each_cpu() stuff to pick up each thread.
Then you may actually get to talk to the right process.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.13.4 on an i686 machine (5589.55 BogoMips).
Warning : 98.36% of all statistics are fiction.
.

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