[PATCH 2/2] ftrace - add ftrace function_graph support on ARM

[Rabin Vincent]

On Mon, Oct 11, 2010 at 1:55 PM, Russell King - ARM Linux
<linux at arm.linux.org.uk> wrote:
> And now to go back to the original question I asked: What is __irq_entry
> used for?

It's used to identify when we're inside the interrupt handling path.
Depending upon the tracing options ("funcgraph-irqs"), this can be
excluded from the trace output.

> If it's to identify those functions which can't be traced through because
> of the stack layout, that's true of all __exception marked functions -
> so we might as well make the linker symbols for irqentry alias the
> exception text symbols.
>
> I see nothing special of just the three functions you mention that warrant
> them being handled separately by ftrace.

See above.  The funcgraph-irqs option is supposed to only affect the
interrupt handling path, not all exception handling.