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SubjectRe: [PATCH] powerpc/irq: Run softirqs off the top of the irq stack
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On Mon, 2013-09-23 at 17:56 +1000, Stephen Rothwell wrote:
> Hi Ben,
>
> On Mon, 23 Sep 2013 14:35:58 +1000 Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> >
> > diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
> > index c69440c..0c9646f 100644
> > --- a/arch/powerpc/kernel/irq.c
> > +++ b/arch/powerpc/kernel/irq.c
> > @@ -443,46 +443,7 @@ void migrate_irqs(void)
> >
> > static inline void handle_one_irq(unsigned int irq)
> > {
> > - struct thread_info *curtp, *irqtp;
> > - unsigned long saved_sp_limit;
> > - struct irq_desc *desc;
> > -
> > - desc = irq_to_desc(irq);
> > - if (!desc)
> > - return;
> > -
> > - /* Switch to the irq stack to handle this */
> > - curtp = current_thread_info();
> > - irqtp = hardirq_ctx[smp_processor_id()];
> > -
> > - if (curtp == irqtp) {
> > - /* We're already on the irq stack, just handle it */
> > - desc->handle_irq(irq, desc);
> > - return;
> > - }
> > -
> > - saved_sp_limit = current->thread.ksp_limit;
> > -
> > - irqtp->task = curtp->task;
> > - irqtp->flags = 0;
> > -
> > - /* Copy the softirq bits in preempt_count so that the
> > - * softirq checks work in the hardirq context. */
> > - irqtp->preempt_count = (irqtp->preempt_count & ~SOFTIRQ_MASK) |
> > - (curtp->preempt_count & SOFTIRQ_MASK);
> >
> > - current->thread.ksp_limit = (unsigned long)irqtp +
> > - _ALIGN_UP(sizeof(struct thread_info), 16);
> > -
> > - call_handle_irq(irq, desc, irqtp, desc->handle_irq);
> > - current->thread.ksp_limit = saved_sp_limit;
> > - irqtp->task = NULL;
> > -
> > - /* Set any flag that may have been set on the
> > - * alternate stack
> > - */
> > - if (irqtp->flags)
> > - set_bits(irqtp->flags, &curtp->flags);
> > }
>
> This function ends up as a single blank line ...
>
> > @@ -519,18 +480,64 @@ void do_IRQ(struct pt_regs *regs)
> > */
> > irq = ppc_md.get_irq();
> >
> > - /* We can hard enable interrupts now */
> > + /* We can hard enable interrupts now to allow perf interrupts */
> > may_hard_irq_enable();
> >
> > /* And finally process it */
> > - if (irq != NO_IRQ)
> > - handle_one_irq(irq);
>
> then you remove the only call, so why not just remove the function
> completely?

Because I'm an idiot ? :-)

I moved bits and pieces to do_IRQ and forgot to remove the remainder
(and gcc didn't warn :-)

Cheers,
Ben.





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