Steve Graegert wrote:
your questions can be answered in very great detail and fill whole
books (which has actually happened), so please forgive my brief
answers.
Brief answers are sufficient. Thank you. :)
and the init process (PID 1) separately. The scheduler then takes
control over the system as soon as the kernel goes idle and init
starts the /etc/rc.d/rc.sysinit script.
So would the kernel be "reawakened" by some external event occurring, as
Glynn wrote? I am thinking like -- the kernel is a body of instructions,
just like any other program. So like I do something (type "cp" at a
terminal, for ex) to have the program called "cp" to be processed --
that is, the instructions in it are executed. Similarly when a system
call is made by any program, the instructions contained in the kernel
would be executed. Is this understanding right?
When a system call is invoked, the process which has invoked is being
interrupted and all the information needed to continue this process is
stored for later use. Now, the process executes higher privileged
code that determines what to do next from examining the stack of the
less privileged code. It contains information about the request to be
served by the kernel. When it is finished, it control is returned to
the program, restoring the saved state and continuing program
execution.
So technically the kernel instructions would be processed "in" the same
process and thread that makes the system call, albeit with different
privelege, right? Or is the process *making the system call* totally
"paused", as in a "wait" situation when one process waits for another to
finish?
Do I also understand right that the kernel resides in a special section
of memory the boot loader puts it in? The core of the kernel (apart from
dynamically loadable kernel modules) is the vmlinuz file sitting in my
/boot dir, right?
Yes, I know. You are a well known member of this list. No need to apologize.
Oh thanks -- that was very nice of you to say. I only thought -- these
are probably very basic questions for my friends here, and so may seem
like homework questions. :)
Have a nice day, all! :)
Shriramana Sharma.
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