On Fri, 2013-02-15 at 16:13 -0800, H. Peter Anvin wrote:
> How important is it that the tracepoint is *inside* the enter/exit
> handling? If not, it would be simpler to just do:
>
> smp_trace_irq_handler()
> {
> trace_irq_entry();
> smp_irq_handler();
> trace_irq_exit();
> }
>
> ... which seems a bit cleaner. If this isn't possible, then this patch
> is fine, but please add to the patch description why the simple wrapper
> isn't doable.
The problem is with irq_enter/exit() being called. They must be called
before trace_irq_enter/exit(), because of the rcu_irq_enter() must be
called before any tracepoints are used, as tracepoints use rcu to
synchronize.
Now perhaps we could do this and have trace_irq_entry().
Not only that, the tracepoint callbacks expect irq_enter() to already be
called.
Hmm, if irq_enter() can nest, which I think it can, perhaps we can call
irq_enter() first. I'm not sure if that will screw up the second
irq_entry() inside smp_irq_handler().
smp_trace_irq_hander()
{
irq_entry();
trace_irq_entry();
smp_irq_handler();
trace_irq_exit();
irq_exit();
}
-- Steve
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
