I've got a little problem I need some help to solve.
For the USB driver, there's an special part of the driver
which needs to act as a daemon. It could be done as a user level
daemon, which I consider to be a mess, as it would not have direct
access to the USB kernel structures, so I'd like to implement it as a
kernel thread, such as kswapd.
Surfing trough /usr/src/linux I see the start code for kswapd,
a call to kernel_thread() defined at asm/unistd.h. It contains an
scary warning which I'm not too able to interpret:
/*
* This is the mechanism for creating a new kernel thread.
*
* NOTE! Only a kernel-only process(ie the swapper or direct descendants
* who haven't done an "execve()") should use this: it will work within
* a system call from a "real" process, but the process memory space will
* not be free'd until both the parent and the child have exited.
*/
You see: the process I'll follow for the creation of this thread is
when the USB Driver Module is loaded, it initializes, registers hosts
and launches the hub driver daemon (aka: khubdd) to handle the device
plugin service and bus enumeration. Thus, I see it is not launched by
a kernel only process and then the proccess memory space won't be
freed until the parent and kid are over.
However, I don't know much about the internals of the module
loading stuff, so I do not what effects will this have. Could anybody
enlighten me?
Also I need to know if there's a way to terminate a kernel
thread (friendly, killing ...) and a way to attach to it to wait for
it's termination. I haven't been able of finding it if exists ...
Thanks in advance for your help!
Yep!
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