[uml-devel] Question about trap handling in UML kernel

[uml-devel] Question about trap handling in UML kernel

[Haifeng He]

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Hi, All

I have a question about trap handling in UML kernel, particularly in the
skas0 mode.
My understanding is that, UML will fork a kernel thread for each user
process and
this thread will go to a loop (in userspace()) and wait for signal from user
process using
ptrace. If a signal occurs, it will call the signal handler to handle the
interrupt.
Is it correct?

My second question is, how many kernel threads are there in skas0 mode or I
should
ask how many different kinds of kernel threads will be created? Is there any
kernel thread
in UML other than those created for user process?

My last question is, given a kernel thread, if it is possible that the
execution of a thread will
be interrupted by others other than by scheduler?

Thank you

Haifeng

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Re: [uml-devel] Question about trap handling in UML kernel

[Jeff Dike]

On Wed, Apr 11, 2007 at 07:10:36PM -0700, Haifeng He wrote:

> I have a question about trap handling in UML kernel, particularly in the
> skas0 mode.
> My understanding is that, UML will fork a kernel thread for each user
> process

UML will fork a host process for each UML address space.

> and
> this thread will go to a loop (in userspace()) and wait for signal from user
> process using
> ptrace. If a signal occurs, it will call the signal handler to handle the
> interrupt.
> Is it correct?

Yes.

> My second question is, how many kernel threads are there in skas0 mode or I
> should
> ask how many different kinds of kernel threads will be created? Is there any
> kernel thread
> in UML other than those created for user process?

There are these kinds, assuming you mean host threads -
	kernel process, runs kernel code - one per virtual CPU
	user process, runs userspace code, one per address space
	utility threads, things that are useful to have in separate
threads, like the I/O thread and SIGIO thread.

> My last question is, given a kernel thread, if it is possible that the
> execution of a thread will
> be interrupted by others other than by scheduler?

If I understand the question, no.

				Jeff

-- 
Work email - jdike at linux dot intel dot com

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