Date: Thu, 3 Jun 2004 00:18:04 -0700
From: Andrew Morton <akpm@osdl.org>
To: Dmitry Torokhov <dtor_core@ameritech.net>
Cc: linux-kernel@vger.kernel.org, greg@kroah.com, vojtech@suse.cz
Subject: Re: [RFC] Changing SysRq - show registers handling
Message-Id: <20040603001804.750b7fa5.akpm@osdl.org>
In-Reply-To: <200406030208.19612.dtor_core@ameritech.net>
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	<200406030208.19612.dtor_core@ameritech.net>
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Dmitry Torokhov <dtor_core@ameritech.net> wrote:
>
> > do_IRQ(...)
>  > {
>  > 	...
>  > 	struct pt_regs **cpu_regs_slot = __get_cpu_var(global_irq_regs);
>  > 	struct pt_regs *save = *cpu_regs_slot;
>  > 	*cpu_regs_slot = &regs;
>  > 	...
>  > 	*cpu_regs_slot = save;
>  > }
>  > 
>  > And to teach the sysrq code to grab *__get_cpu_var(global_irq_regs).
> 
>  Ok, so by making it a tad slower you can keep the old semantics - printing
>  registers right when keyboard interrupt is processed instead of waiting till
>  the next one arrives.
> 
>  Hmm... the path is pretty hot, I am not sure what is best.

Well bear in mind that we can then rip all the pt_regs passing out from
everywhere, so as long as you edit every IRQ handler in the kernel it's a
net win ;)

I _think_ it'll work - as long as all architectures go through a common
dispatch function like do_IRQ(), which surely they do.  The above code
could be an arch-neutral inline actually.

I'm not sure what's best really.  But something this general is more
attractive than something which is purely for sysrs-T.
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