linux-kernel - Re: [PATCH 1/6 v6] SGI RTC: add generic system interrupt

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Date:	Tue, 3 Mar 2009 16:34:33 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Dimitri Sivanich <sivanich@....com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	john stultz <johnstul@...ibm.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6 v6] SGI RTC: add generic system interrupt


* Dimitri Sivanich <sivanich@....com> wrote:

> This patch allocates a system interrupt vector for various 
> platform specific uses.

this is really ugly.

Also, why are all these symbols exported? There's no need to 
build the UV RTC driver as a module. It's either built-in or not 
built-in - it's small enough.

this stuff:

> +/* Function pointer for generic interrupt vector handling */
> +static void (*generic_interrupt_extension)(void);
> +static char generic_show_string[28];
> +static char generic_show_prefix[6];
> +
> +int is_generic_interrupt_registered()
> +{
> +	if (generic_interrupt_extension)
> +		return 1;
> +	else
> +		return 0;
> +}
> +
> +char *generic_interrupt_string(void)
> +{
> +	return generic_show_string;
> +}
> +
> +char *generic_interrupt_prefix(void)
> +{
> +	return generic_show_prefix;
> +}

is SMP unsafe, etc. etc. - not something we should ever call 
from a module. We just shouldnt do it in this form. What 
necessiates it?

All we need is:

> +	/* generic IPI for platform specific use */
> +	alloc_intr_gate(GENERIC_INTERRUPT_VECTOR, generic_interrupt);

plus one trivial callback function - and then the UV platform 
uses it for its own purpose. It's not like two platforms will be 
running at once so there's no locking needed, etc.

> +#ifdef CONFIG_X86_64
> +extern void generic_interrupt(void);
> +#endif

in any case please make it symmetric across 32-bit and 64-bit - 
even though UV is 64-bit only.

	Ingo
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