[lttng-dev] Lttng-UST behavior issue (potential bug in lttng-tools)

Sebastien Boisvert sboisvert at gydle.com
Mon Nov 28 16:09:24 UTC 2016

Hi all,

I am tracing a C++ application on a 32-core machine (2 x AMD Opteron 6376 16 cores, 256 GB RAM).

I found a bug in lttng-tools.

After 5 tracing sessions, the session number 6 (the sixth session, starting in a state where no lttng* daemons
are running, always crash (n = 10) at "lttng enable-event" ("UST create channel failed").
Because of this, lttng throws an error and does not seem to do a health check or to be able to recover from this.
I know that the problem is in one of the daemons because if I kill them all the problem goes away.

I searched "UST create channel failed" on https://bugs.lttng.org/, and got 1 search result (no
open bugs):

- https://bugs.lttng.org/issues/339 ("Subbuffer size of < 4096 are accepted but unable to use the channel afterwards")

Here is my bug report:



I can help with the fix.

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