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Bug #1170

Using the --output flag with the new dynamic tracing feature in 2.11 causes the trace to be lost / no output produced

Added by Deborah Barnard over 1 year ago. Updated over 1 year ago.

Status:
Resolved
Priority:
Normal
Assignee:
-
Target version:
Start date:
11/13/2018
Due date:
% Done:

100%

Estimated time:

Description

Running the example provided in the release notes (https://github.com/lttng/lttng-tools/releases/tag/v2.11.0-rc1), I believe I found a bug when setting a custom trace output path.

The following worked as expected. The trace was written to the default location (lttng-traces/demo-session-<timestamp>).

sudo lttng create demo-session
sudo lttng enable-event --kernel --userspace-probe /lib/x86_64-linux-gnu/libc-2.23.so:malloc libc_malloc
sudo lttng start

[do various actions]

sudo lttng stop
sudo lttng destroy

The following resulted in no trace file being produced:

sudo lttng create demo-session --output=/tmp/demo-session
sudo lttng enable-event --kernel --userspace-probe /lib/x86_64-linux-gnu/libc-2.23.so:malloc libc_malloc
sudo lttng start

[do various actions]

sudo lttng stop
sudo lttng destroy

The problem also applied if I set it to use the default directory:

sudo lttng create demo-session --output=/lttng-traces/demo-session
sudo lttng enable-event --kernel --userspace-probe /lib/x86_64-linux-gnu/libc-2.23.so:malloc libc_malloc
sudo lttng start

[do various actions]

sudo lttng stop
sudo lttng destroy

I am expecting to be able to set a custom output path based on the 2.10 documentation (https://lttng.org/docs/v2.10/#doc-tracing-the-linux-kernel)
I made sure to do exactly the same actions for each test.

#1

Updated by Mathieu Desnoyers over 1 year ago

  • Project changed from LTTng-modules to LTTng-tools
#2

Updated by Francis Deslauriers over 1 year ago

Hi Deborah,

Thanks for the report. Could you simply try to same commands you run in steps 2 and 3 but replacing the enable-event command with the following

lttng enable-event -a -k

I want to know if it's related specifically to the new --userspace-probe feature or not.

Also, I don't know if it was a typo when you filed the bug report but the path you supplied for your 3rd testcase has a missing `~` to be the default $HOME/lttng-traces directory.

Cheers,

#3

Updated by Deborah Barnard over 1 year ago

My apologies. I was a little trigger-happy with the bug report.

#4

Updated by Francis Deslauriers over 1 year ago

Deborah Barnard wrote:

My apologies. I was a little trigger-happy with the bug report.

What do you mean? You fixed the issue?

#5

Updated by Deborah Barnard over 1 year ago

Yes - it was very much a human error. Sorry again!

#6

Updated by Francis Deslauriers over 1 year ago

  • Status changed from New to Resolved

No problem.

#7

Updated by Francis Deslauriers over 1 year ago

  • % Done changed from 0 to 100

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