Re: interrupt handler
george anzinger (firstname.lastname@example.org)
Fri, 23 Aug 2002 13:45:05 -0700
Robert Love wrote:
> On Fri, 2002-08-23 at 12:45, Richard B. Johnson wrote:
> > On 23 Aug 2002, Robert Love wrote:
> > > Only the current interrupt handler is disabled... interrupts are
> > > normally ON.
> > No. Check out irq.c, line 446. The interrupts are turned back on
> > only if the flag did not have SA_INTERRUPT set. Certainly most
> > requests for interrupt services within drivers have SA_INTERRUPT
> > set.
> Sigh... SA_INTERRUPT is used only for fast interrupts. Certainly most
> drivers do not have it (and most that do are probably from the way old
> days when we went through great pains to distinguish between fast and
> slow interrupt handlers).
> Today, very few things should run with all interrupts disabled. That is
> just dumb. In fact, on this system, it seems only the timer interrupt
> sets SA_INTERRUPT...
And THAT makes sense as most of the timer interrupt is
processed holding the write_lock() on xtime which would need
to be an irq lock otherwise. If they were turned on the
system would have an additional interrupts on/off overhead.
> Robert Love
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George Anzinger firstname.lastname@example.org
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