Messages in this thread | | | Date | Fri, 6 Oct 2017 09:07:11 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v7 2/2] tracing: Add support for preempt and irq enable/disable events |
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On Thu, Oct 05, 2017 at 04:28:10PM -0700, Joel Fernandes wrote: > > lockdep implements the trace_hardirq_*() in terms of *_caller(). Would > > that make sense here? > > In lockdep code, when trace_hardirqs_off is called, > trace_hardirqs_off_caller would pass CALLER_ADDR0 as > trace_hardirqs_off. > > Because of this, the first argument passed to time_hardirqs_off would > always be an offset within trace_hardirqs_off: > time_hardirqs_off(CALLER_ADDR0, ip); > > Is that intended? Seems to me that in the lockdep implementation of > trace_hardirqs_* in terms of *_caller(), we would completely miss the > second-last return address (CALLER_ADDR1) of trace_hardirqs_off(). > Also for the above reasons, I don't think it doesn't make sense to use > this reuse logic for the tracer. Atleast I feel it might change the > current behavior of the preempt/irqsoff tracer which I don't intend to > change with my current patch set.
Hurm.. so I've no clue. I never looked at any of this. I think Ingo wrote that before I came joined the fun. He might (although unlikely, because its been _many_ years) still have some memories.
But given that lockdep enabled kernels never got those arguments right, how useful are they? I mean, nobody seems to have noticed much.
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