Kernelnewbies Digest, Vol 63, Issue 20

[Mulyadi Santosa]

On Mon, Feb 15, 2016 at 10:47 AM, Vishwas Srivastava <vishu.kernel at gmail.com
> wrote:

>
> On Sun, Feb 14, 2016 at 9:16 AM, tobaccopipeyoyo . <
> tobaccopipeyoyo at gmail.com> wrote:
>
> > Hi,
> > I'm new to kernel programming, currently started ldd book
> > For the current process it says that global item current returns the
> > task_struct of the currently running process.
> >
> > What if I refer this global during interrupt servicing?
> > What will happen? What should I expect.
> >
> > Thanks,
> > tpyy
> >
> >
> Hi...
>
> during interrupt servicing, "current" will give you last process' data
> structure that's get interrupted by the interrupt. Of course, this is per
> cpu context, so if you are in SMP situation, current will return task
> struct in that CPU only.
>
> The essential thing in interrupt servicing is: interrupt handler runs on
> behalf of current running process.
>
> Hopefully I still recall all these correctly.
>
>
> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> Hi Mulyadi,
>                     I disagree with the statement you made here that
> "interrupt handler runs on behalf of current running process".
> Your statement is valid for system calls (software interrupt) but not for
> the real "interrupt"
> Interrupt handler are nowhere related to any process. They run their own
> without caring about
> which process was running.
> --- Vishwas
>
>
>
Hello Vishwas

Thank you for your correction.

You're correct. Maybe my wording is not exactly correct. My intention was
to point that especially during bottom half interrupt servicing, if you run
call "current", it will point to last process before kernel switch to
kernel mode servicing the interrupt. So the word "on behalf" is not exactly
correct, I admit that.

Feel free to correct if I am still wrong...



-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com
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