i think you would use kernel threads in driver when you want to do
something in a process context, not in a syscall.
>>>> wanting to do something in process context means that I would like to
do something during which i might sleep ?
regards
Amit
Anupam Kapoor <anupam.kapoor@gmail.com>@nl.linux.org on 06/30/2004 03:52:28
PM
Sent by: kernelnewbies-bounce@nl.linux.org
To: Amit Kumar Singh/HSS@HSS
cc: Jan Hudec <bulb@ucw.cz>, Anandraj <arm@tataelxsi.co.in>,
kernelnewbies@nl.linux.org
Subject: Re: kernel threads
On Wed, 30 Jun 2004 15:01:24 +0530, aksingh@hss.hns.com
<aksingh@hss.hns.com> wrote:
>
>
> so what are the differences between a kernel module and kernel threads
they are _very_ different...to paraphrase from an old poem
"a module is a module, a kernel_thread is a kernel_thread and never
shall the twain meet !"
i hope you meant, a 'kernel thread' and a 'userland process'. a kernel
thread has no userspace context in it (as i said earlier, it's mm
pointer is NULL etc.), they operate in kernel space _only_
###### yes i meant userland process #############
> , as
> you said kernel threads can be scheduled, pre-empted and all.that is one
> Whats the utility of kernel threads, do drivers generally use them or if
I
> put it in a better way, when should someone think of using kernel threads
> in his/her modules?
i think you would use kernel threads in driver when you want to do
something in a process context, not in a syscall. there must be bunch
of kernel threads running on your system. for me, i have things like:
#### wanting to do something in process context means that I would like to
do something during which i might sleep ? ##
pdflushd : responsible for writing dirty pages to disk. earlier this
was done via the bdflush and kupdated.
ksoftirqd: helps processing of softirqs
to name a few.
kind regards
anupam
>
> thanks
> Amit
>
> Anupam Kapoor <anupam.kapoor@gmail.com> on 06/30/2004 02:55:43 PM
>
> To: Jan Hudec <bulb@ucw.cz>
> cc: Amit Kumar Singh/HSS@HSS, Anandraj <arm@tataelxsi.co.in>,
> kernelnewbies@nl.linux.org
>
> Subject: Re: kernel threads
>
>
>
>
> also, kernel threads have their mm pointer set to NULL. kernel threads
> are schedulable, preemptible etc. just like normal processes.
>
> anupam
>
> On Wed, 30 Jun 2004 10:55:40 +0200, Jan Hudec <bulb@ucw.cz> wrote:
> > On Wed, Jun 30, 2004 at 13:15:23 +0530, aksingh@hss.hns.com wrote:
> > > i read that already, there the programmer has used his own functions
to
> > > create threads and all, i just wanted to know if kernel threads are
> > > standard features and if kernel provides some functions to create,
> destroy
> > > them, because I never came across them in linux till now. I dont
think
> > > drivers create different threads, correct ?
> >
> > Kernel threads are created, surprisingly, with a function
> > kernel_thread(). Then they need to call daemonize() to fully get rid of
> > their userland and reparent to init, because they are created by
cloning
> > whatever process happens to be current.
> >
> >
>
-------------------------------------------------------------------------------
>
> > Jan 'Bulb' Hudec
> <bulb@ucw.cz>
> >
> >
> >
>
>
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