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

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Date:	Fri, 20 Sep 2013 11:26:13 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
cc:	Andreas Schwab <schwab@...ux-m68k.org>,
	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 Thu, 19 Sep 2013, Geert Uytterhoeven wrote:

> On Thu, Sep 19, 2013 at 7:02 PM, Andreas Schwab <schwab@...ux-m68k.org> wrote:
> > Thomas Gleixner <tglx@...utronix.de> writes:
> >> +     /*
> >> +      * Only the last interrupt leaving the kernel goes through the
> >> +      * various exception return checks.
> >> +      */
> >> +     cmpl    #0, %d0
> >         tstl    %d0
> 
> arch/m68k/kernel/built-in.o: In function `bad_inthandler':
> (.text+0x2a6): undefined reference to `ret_from_last_interrupt'
> 
> I came up with the quick (whitespace-damaged-gmail) fix below.
> Or should we handle the nesting in handle_badint(), too?

Hmm, probably yes. If a badint gets interrupted by a good one, you
would fail to go through ret_from_exception.
 
> --- a/arch/m68k/kernel/entry.S
> +++ b/arch/m68k/kernel/entry.S
> @@ -313,17 +313,11 @@ user_irqvec_fixup = . + 2
> 
>  ENTRY(bad_inthandler)
>         SAVE_ALL_INT
> -       GET_CURRENT(%d0)
> -       movel   %d0,%a1
> -       addqb   #1,%a1@(TINFO_PREEMPT+1)
> 
>         movel   %sp,%sp@-
>         jsr     handle_badint
>         addql   #4,%sp
> 
> -       movel   %curptr@(TASK_STACK),%a1
> -       subqb   #1,%a1@(TINFO_PREEMPT+1)
> -       jeq     ret_from_last_interrupt
>         RESTORE_ALL
> 
> However, the resulting kernel hangs (on ARAnyM) after starting userspace:
> 
> | INIT: version 2.86 booting

Hmm.
 
> I'll have a deeper look when I have some more time...

Thanks a lot!

       tglx
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