Bug #793: lttng stop never finishes when using overwrite mode (not in snapshot mode) - LTTng-tools - LTTng bugs repository

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Bug #793

closed

lttng stop never finishes when using overwrite mode (not in snapshot mode)

Added by Jérémie Galarneau over 10 years ago. Updated over 10 years ago.

Status:

Resolved

Priority:

High

Assignee:

David Goulet

Target version:

LTTng - 2.3

Start date:

04/29/2014

Due date:

% Done:

100%

Estimated time:

Description

The lttng stop command never stops waiting for data availability with the following command sequence.

[jgalar@XThink ~/lttng-traces]$ lttng create test
Session test created.
Traces will be written in /home/jgalar/lttng-traces/test-20140429-172712
[jgalar@XThink ~/lttng-traces]$ lttng enable-channel test-chan -k --subbuf-size 12M --num-subbuf 1 --overwrite
Warning: The subbuf size (12582912) is rounded to the next power of 2 (16777216)
Kernel channel test-chan enabled for session test
[jgalar@XThink ~/lttng-traces]$ lttng enable-event -k -a -c test-chan
All Kernel events are enabled in channel test-chan
[jgalar@XThink ~/lttng-traces]$ lttng start
Tracing started for session test
[jgalar@XThink ~/lttng-traces]$ lttng stop
Waiting for data availability...............................................................................................................................................................................................................................................
pre>

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Updated by David Goulet over 10 years ago

Status changed from New to Confirmed
Priority changed from Normal to High
Target version changed from 2.5 to 2.3

There seems to be an issue with the --overwrite alone where in 2.4 and master, --snapshot is used for the purpose of flight recorder. One thing certain is that you can't use this option with a session with an output defined thus the enable-channel should have fail because the session is not set in --no-output.

I'm also going to link this one with the open issue for the deprecation of --no-output

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Updated by David Goulet over 10 years ago

After investigation, the flush/stop of the kernel in overwrite mode does not actually write data on disk (not even the padding) thus the "output_written" of the stream always equal 0 which keeps the data pending in a loop waiting for at least some data.

A destroy fixes the issue and provide a readable trace but only stops actually makes the trace unreadable.

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