Re: sharing data (can ISR be pre-empted???)(continue)

[prasanna wakhare <prasannawakhare@xxxxxxxxx>]

hi,
Yes the ISR have priority sets,rather PIC itself has
priorities ,so high priority ISR can preempt low one,

ANd not all handlers disables the interrupt in case
handler is fast and time critical then a flag is set
i think SA_INTERRUPT flag which i think works on SMP 
also,
and most of the other handlers cant disables the
interrupt while executing and can be preepmted by
another high prioroty interrupt,an example you can
 say thar IRQ0 timer handler has got highest priority
so it can preempt other handler.
Please correct if any mistake
thanks
Prasanna

--- mandeep sandhu <msandhu_d@xxxxxxxxxxx> wrote:
> can another ISR preempt the current executing ISR!
> during execution of ISR's are'nt the interrupts
> disabled?
> 
> do ISR's also have priority associated with them???
> 
> i think b4 executing an ISR the kernel calls
> "preempt-disable"
> (not very sure though....)???
> 
> - /dev/mandeep
> 
> 
> mandeep sandhu wrote:
> >hi all,
> >i've heard that the linux kernel is preemptive from
> 2.5 onwards....
> >so can an ISR be preempted by the kernel. as i
> understand an ISR doest not
> >have a process context, so then what can preempt
> it????
> 
> Yes you're right. An ISR has no process context. But
> an ISR can be
> interrupted by some code lika for example another
> ISR. Interrupts can be
> nested in Linux (even in 2.4).
> And in 2.5 and 2.6, ISR can be preempted by a thread
> or anything else
> which has a higher priority.
> 
> 
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