Re: Why can't we sleep in an ISR?

["pradeep singh" <2500.pradeep@gmail.com>]

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On 15 May 2007 09:34:23 -0000, rohit hooda <rohit13hooda@rediffmail.com>
wrote:
>
>
>
>
> On Tue, 15 May 2007 pradeep singh wrote :
> >On 5/14/07, Bahadir Balban <bahadir.balban@gmail.com> wrote:
> >>
> >>On 5/14/07, Learning Linux <learninglinux4@gmail.com> wrote:
> >> > Ok, but how about an ISR, that does not take any locks? Why can't we
> >> > sleep in SUCH an ISR?
> >> > LL
> >> > -
> >>
> >>The killer reason why you can't sleep in an interrupt is because an
> >>interrupt is not associated with any context in the first place.
> >
> >
> >good enough, but i have a query regarding this then.
> >On a 8K kernel stack system, doesn't interrupts share the stack
> associated
> >with the current process which was interrupted?
> Yes, you are right.
> >Doesn't interrupt steals the CPU slice time allocated to the running
> process
> >to run?
> Yes
> >Doesn't it run in current process's context ?
> You got it worng here. It runs on behalf of the process, but in the
> current process's context.
> For interrupts we have a dirrerent context altogether.
>
Ok, that explains a bit.
how will you define an interrupt context?

Thanks
~psr

>
> >What am i missing here?
> There are two different contexts of execution
> Process context
> Interrupt context
> >
> >Thanks
> >~psr
> >
> Thanks,
> -Rohit
> >What
> >>is a context, then? It is the state information for a process. This
> >>includes the kernel and userspace stack pointers, the register set,
> >>and the page tables for that process. The scheduler has access to all
> >>this information, to preempt one process and run another. Contrary to
> >>this, an interrupt, depending on the version of your kernel and arch,
> >>uses a separate irq stack or the kernel stack of the interrupted
> >>process. An irq is not a context but merely a temporary execution to
> >>be concluded asap.
> >>
> >>Hope this helps,
> >>Bahadir
> >>
> >
> >
> >
> >-- play the game
>
>
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-- 
play the game

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