Re: [PATCH] genirq: ARM dyntick cleanup

[Andrew Morton <akpm@osdl.org>]

On Mon, 3 Jul 2006 10:03:43 +0100
Russell King <rmk+lkml@arm.linux.org.uk> wrote:

> On Mon, Jul 03, 2006 at 12:55:42AM -0700, Andrew Morton wrote:
> > On Mon, 3 Jul 2006 08:41:55 +0100
> > Russell King <rmk+lkml@arm.linux.org.uk> wrote:
> > 
> > > On Sun, Jul 02, 2006 at 05:35:27PM -0700, Andrew Morton wrote:
> > > > This is not exactly a thing of beauty either.  It's much cleaner to use
> > > > __attribute__((weak)), but that will add an empty call-return to everyone's
> > > > interrupts.
> > > 
> > > Let's not go overboard with the weak stuff - it does not get removed
> > > at link time, so it remains as dead code in the kernel image.
> > 
> > Well.
> > 
> > void handle_dynamic_tick(struct irqaction *action)
> > {
> > }
> > 
> > consumes one byte, doesn't it?  That's not very far overboard ;)
> 
> ROTFL!
> 
> All the word isn't x86.  On ARM it's 3 words for the stack setup and
> one for the tear down, so 16 bytes, assuming the function doesn't
> return a value.  If it does, add another 4 bytes.
> 

Well yes, and there's also compiler-added alignment padding after the
function itself.

It's still pretty small beer.  It's a judgement call, which is why I
recommended it not be used here.

A lot of places where it's used (and useful) are in __init setup code.