Fixed
Created: Feb 9, 2020
Updated: May 14, 2020
Resolved Date: Apr 20, 2020
Previous ID: LINLTS-1061
Found In Version: 8.0.0.32
Fix Version: 8.0.0.33
Severity: Standard
Applicable for: Wind River Linux 8
Component/s: Userspace
Instrumented lttng-libraries causes stderr pollution when an lttng-ust error occurs. Most of the lttng ust info, debug and error messages are put behind an environment variable, however not all. This issue is fixed in lttng-ust v2.7, see changelog lttng-ust v2.7: Don't output to stderr from lib unless DEBUG is activated.
A demo program, demo.sh which starts and configures the lttng-sessiond, and invokes two binaries which trigger the issues we are encountering (however, more different errors can be thrown). To reproduce our issue, please extract lttng_stderr_pollution.zip, and run demo.sh. The source code of the binaries called (including build instruction comments) are included as well.
Without this fix, we will suffer from error messages when e.g. a process, uses an instrumented library, does not pre-load lttng-ust-fork lib when forking. Also, when the system is under heavy load, tracepoint registration does not always succeed the first time, and causes timeout messages to be thrown, impacting system behavior.
