[tor-bugs] #32910 [Core Tor/Tor]: trace: Add tracepoints and userspace tracer support

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#32910: trace: Add tracepoints and userspace tracer support
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 Reporter:  dgoulet       |          Owner:  dgoulet
     Type:  enhancement   |         Status:  needs_revision
 Priority:  Medium        |      Milestone:  Tor: 0.4.4.x-final
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:  tracing       |  Actual Points:
Parent ID:                |         Points:  3
 Reviewer:  nickm         |        Sponsor:
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Comment (by dgoulet):

 Replying to [comment:9 nickm]:
 > Can you explain why we need TRACEPOINT_HEADER_MULTI_READ ?

 That is LTTng specific. LTTng, at compile time, create the tracing probes
 (basically the C code to handle tracepoints) and uses that include file to
 get their declaration and type for parameters.

 However, LTTng has a lot of trickery to create those probes, that are
 hidden from us, except this one in particular which is a way to override
 the header file guard macro so the header can be included multiple times
 for probe creation.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32910#comment:10>
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