Messages in this thread | | | Subject | Re: [PATCH v9 3/3] trace,x86: code-sharing between non-trace and trace irq handlers | From | Steven Rostedt <> | Date | Fri, 15 Feb 2013 20:25:02 -0500 |
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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
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