Re: [lttng-dev] Trying to understand use of lttng enable-event --kernel --userspace-probe=
Mathieu Desnoyers via lttng-dev <[email protected]>
| Newsgroups | org.lttng.lists.lttng-dev |
|---|---|
| Message-ID | <[email protected]> |
On 2023-05-18 15:07, Brian Hutchinson wrote: [...] >> >> If you attach to an ELF symbol (function), then there is no USDT in >> play, so it should not be related to the issue you have. > > That is what I was thinking which is why I wanted to try it. > >> >> But if your functions happen to be inlined, then there will be nothing >> to attach to. Perhaps this is what happens there ? > > I don't see any evidence of anything being inlined in this module. I > grepped the code to verify. > > Back to being stumped/stuck. Make sure to check the resulting assembler and ELF symbol tables. The compiler is free to inline various functions unless they are explicitly marked as __attribute__((noinline)). Also, if LTO is enabled, further optimization can be done at link-time. One purpose of the UST tracepoints is to be less fragile with respect to specific optimizations done by the compiler and linker, thus guaranteeing that whatever is instrumented with a tracepoint is indeed available for tracing. Also, double-check that the path you pass to --userspace-probe really targets your executable or .so binary file, and is not just a symbolic link. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev