lkml.org 
[lkml]   [2006]   [Jun]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: i386 IPI handlers running with hardirq_count == 0

* Keith Owens <kaos@ocs.com.au> wrote:

> My question has nothing to do with NMI. I am querying inconsistent
> behaviour amongst normal IPIs, this list :-
>
> i386 function irq_enter?
> smp_apic_timer_interrupt yes
> smp_call_function_interrupt yes
> smp_error_interrupt yes
> smp_invalidate_interrupt no - why
> smp_reschedule_interrupt no (does not need it)
> smp_spurious_interrupt yes
> smp_thermal_interrupt yes
>
> x86_64 function irq_enter?
> mce_threshold_interrupt yes
> smp_apic_timer_interrupt yes
> smp_call_function_interrupt yes
> smp_error_interrupt yes
> smp_invalidate_interrupt no - why
> smp_reschedule_interrupt no (does not need it)
> smp_spurious_interrupt yes
> smp_thermal_interrupt yes

irq_enter() is mostly just for the purpose of in_interrupt()/in_irq() to
work as expected, not much else. [also the timer code assumes that
update_process_times() is called in a HARDIRQ_OFFSET elevated context,
so the apic timer IRQ needs irq_enter() too.] The
smp_invalidate_interrupt() and smp_reschedule_interrupt() is
performance-critical and they dont need irq_enter()/irq_exit().

Since smp_call_function_interrupt() can be called with driver-supplied
function vectors, it's best to keep the irq_enter()/exit there. [for
example mm/slab.c has some in_interrupt() sanity checks.] Obviously
do_IRQ() itself needs irq_enter()/exit() too - plus the APIC timer irq
as mentioned above.

Otherwise, the rest of the SMP functions technically dont need
irq_enter()/irq_exit(). [i.e. threshold, error, spurious and thermal] We
could remove it from them.

Ingo
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-06-29 22:25    [W:0.388 / U:0.792 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site