On Wed, Jun 30, 2004 at 15:01:24 +0530, aksingh@hss.hns.com wrote:
> so what are the differences between a kernel module and kernel threads, as
Kernel MODULE and kernel THREAD are completely distinct things.
I assume you meant between a kernel thread and a process. Well, a kernel
thread is a process, that has no user-space code and only runs in
kernel.
> 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?
You use kernel thread in a driver, if you need to do some work in
process context, but not in a syscall.
Briefely looking on my system, there is some 20 kernel threads running.
Some of them, I am not sure what they do. Among the ones I have at least
some idea what they do are:
ksoftirqd: This runs the task_queues.
kswapd0: IIRC this thread does the memory aging and initiates swapping.
aio: This polls for the aio request.
reiserfs: This does the delayed operations in reisterfs. IIRC flushing
dirty nodes is one.
(there are also events, kblockd, khelper and kseriod, but I don't know
what these do)
rpciod: This provides RPC for the NFS client and server.
lockd: This is the NFS lock daemon. It keeps track of files locked over
NFS.
nfsd: This is the nfs server. It does the actual IO requested over NFS.
There is actualy 8 of these.
The first few of them are spawned by kernel proper, the NFS ones are
spawned by the nfsd module.
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Jan 'Bulb' Hudec <bulb@ucw.cz>
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