linux-kernel - Re: [patch 1/6] hardirq: Make hardirq bits generic

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Date:	Tue, 17 Sep 2013 23:24:49 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <ak@...ux.intel.com>, Peter Anvin <hpa@...or.com>,
	Mike Galbraith <bitbucket@...ine.de>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Linux/m68k <linux-m68k@...r.kernel.org>
Subject: Re: [patch 1/6] hardirq: Make hardirq bits generic

On Tue, 17 Sep 2013, Geert Uytterhoeven wrote:

> On Tue, Sep 17, 2013 at 8:53 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> > --- linux-2.6.orig/arch/m68k/include/asm/hardirq.h
> > +++ linux-2.6/arch/m68k/include/asm/hardirq.h
> > @@ -5,17 +5,6 @@
> >  #include <linux/cache.h>
> >  #include <asm/irq.h>
> >
> > -#define HARDIRQ_BITS   8
> 
> > --- linux-2.6.orig/include/linux/preempt_mask.h
> > +++ linux-2.6/include/linux/preempt_mask.h
> > @@ -11,36 +11,22 @@
> >   * - bits 0-7 are the preemption count (max preemption depth: 256)
> >   * - bits 8-15 are the softirq count (max # of softirqs: 256)
> >   *
> > - * The hardirq count can in theory reach the same as NR_IRQS.
> > - * In reality, the number of nested IRQS is limited to the stack
> > - * size as well. For archs with over 1000 IRQS it is not practical
> > - * to expect that they will all nest. We give a max of 10 bits for
> > - * hardirq nesting. An arch may choose to give less than 10 bits.
> > - * m68k expects it to be 8.
> 
> m68k needs some changes in arch/m68k/kernel/entry.S, cfr. this check
> in arch/m68k/kernel/ints.c:
> 
>         /* assembly irq entry code relies on this... */
>         if (HARDIRQ_MASK != 0x00ff0000) {
>                 extern void hardirq_mask_is_broken(void);
>                 hardirq_mask_is_broken();
>         }
> 
> Haven't looked into the details yet...

Whee. Did not notice that one. Though I can't find anything
interesting in the low level entry code... Looks like some more
histerical left overs.

Thanks,

	tglx

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