[lttng-dev] infinite loop invoked using lttng enable/disable-event

[Thibault, Daniel]

-----Message d'origine-----
Date: Tue, 25 Jun 2013 09:49:36 +0300
From: Avi Goren <avi at reduxio.com>

I'm using lttng 2.2.0 and encountered an infinite loop:
-------------------------------------------------------------------------
# lttng create
Session auto-20130624-165047 created.
Traces will be written in /home/avig/lttng-traces/auto-20130624-165047
# lttng enable-event -a -u --loglevel TRACE_ALERT
All UST events are enabled in channel channel0 for loglevel TRACE_ALERT
# lttng enable-event -a -u --loglevel TRACE_CRIT
All UST events are enabled in channel channel0 for loglevel TRACE_CRIT
# lttng disable-event -a -u
All UST events are disabled in channel channel0
# lttng enable-event -a -u --loglevel TRACE_CRIT
All UST events are enabled in channel channel0 for loglevel TRACE_CRIT
# lttng disable-event -a -u
(infinite loop here...)
-------------------------------------------------------------------------
I guess it's probably due to the setting of loglevel through enable-event twice..?
Avi
------------------------------

   I've reproduced it with one less step:

# lttng create loop
Session loop-20130624-165047 created.
Traces will be written in /home/avig/lttng-traces/loop-20130624-165047
# lttng enable-event -a -u --loglevel TRACE_ALERT
All UST events are enabled in channel channel0 for loglevel TRACE_ALERT
# lttng disable-event -a -u
All UST events are disabled in channel channel0
# lttng enable-event -a -u --loglevel TRACE_CRIT
All UST events are enabled in channel channel0 for loglevel TRACE_CRIT
# lttng list loop
(...)
    Events:
      * (loglevel: TRACE_CRIT (2)) (type: tracepoint) [enabled]
      * (loglevel: TRACE_ALERT (1)) (type: tracepoint) [disabled]
# lttng disable-event -a -u
(LTTng hangs here)

   Remarkably, the session daemon remains very busy after the sudo kill command is sent, even though the trace has not even been started!  It refuses to die and I had to restart the system.  I'll post the bug up (with the session daemon log) shortly.

Daniel U. Thibault
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