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Bug #661

lttng snapshot record ignores user-space if kernel is also being traced

Added by Daniel U. Thibault over 6 years ago. Updated about 6 years ago.

Status:
Resolved
Priority:
Normal
Assignee:
Target version:
Start date:
11/15/2013
Due date:
% Done:

0%

Estimated time:

Description

Using:
lttng-modules 2.3.0-1 78c8710
lttng-tools 2.3.0-1 c9dc128
lttng-ust 2.3.0-1 9f00ce3
userspace-rcu 0.8.0-1 ca617ca
on:
Ubuntu 12.04.3 LTS precise,
3.2.0-53-virtual kernel

$ sudo -H lttng create mySession --snapshot
Spawning a session daemon
Session mySession created.
Default snapshot output set to: /root/lttng-traces/mySession-20130925-101114
Snapshot mode set. Every channel enabled for that session will be set in overwrite mode and mmap output.
$ sudo -H lttng enable-event -a -k --syscall
All kernel system calls are enabled in channel channel0
$ sudo -H lttng enable-channel channel0 -u --buffers-uid
$ sudo -H lttng enable-event -a -u -c channel0
$ sudo -H lttng start
Tracing started for session mySession
$ sudo -H lttng snapshot record
Snapshot recorded successfully for session mySession

What is bizarre here is that snapshot record will successfully capture the user-space trace if no kernel tracing is going on. But with kernel tracing active, as in this example, only the kernel domain gets committed to storage. Disabling kernel tracing (in this example by disabling the kernel's channel0 channel) does not help.

#1

Updated by Mathieu Desnoyers about 6 years ago

  • Project changed from LTTng to LTTng-tools
  • Assignee set to David Goulet
#2

Updated by David Goulet about 6 years ago

  • Status changed from New to Resolved
  • Target version changed from 2.4 to 2.3

Also fixed in stable-2.3 upstream.

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