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Bug #1294

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add-context fails silently with perf_event_paranoid=4, no trace produced

Added by Jeff Trull 8 months ago.

Status:
New
Priority:
Normal
Assignee:
-
Target version:
-
Start date:
12/02/2020
Due date:
% Done:

0%

Estimated time:

Description

Desired result:
A disallowed add-context (e.g. because of perf_event_paranoid) produces an error message and a non-zero exit code.

Actual result:
A disallowed add-context produces only a message in the system log, invisible to the normal user.
For example, when perf_event_paranoid forbids it you get a message of the form:

Error: UST app create channel context failed for app (pid: 76220) with ret -1024

But the only effects observable to the user are:

  1. no trace is produced, and
  2. when you destroy the session there is a message like Failed to perform a quiet rotation as part of the destruction of session "..."

If other users are like me they will spend quite some time trying to figure out what is wrong in their code, setup etc. before figuring out what's wrong (or having someone on IRC identify it for them, as in my case).

This is Ubuntu 20.04.1, with lttng-ust 2.11.0

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