allow multiple sessions in ad-hoc `tprof:profile/2`

[ruslandoga]

👋

The goal of this PR is to allow running multiple tprof:profile/2 at the same time without fear of overlap.

I need to:

• [ ] add tests
• [ ] update these docs

---

^{I'm targeting master instead of maint because I did that in https://github.com/erlang/otp/pull/9648 and this PR kind of requires that other one ...}

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[sverker]

The goal of this PR is to allow running multiple tprof:profile/2 at the same time without fear of overlap.

What's the "fear"? Maybe I'm missing something, but the code seems to work fine today. tprof:profile will spawn an unregistered server that creates a new trace session. The name passed to trace:session_create does not need to be unique. Several trace sessions with the same name can exists without interfering each other.

[ruslandoga]

👋

~~The current approach might be working fine because session option was no-op: https://github.com/erlang/otp/pull/9648 -- but it still ended up always being tprof ...~~

Seems like I misunderstood my own change in https://github.com/erlang/otp/pull/9648 :) I'll limit the changes in this PR just to the docs.

Thank you!

[sverker]

Good. This paragraph in the tprof docs does not seem correct:

By default, only one ad-hoc or server-aided profiling session is allowed at any point in time. It is possible to force multiple ad-hoc sessions concurrently, but it is the responsibility of the developer to ensure that trace patterns do not overlap: