[ltt-dev] lttctl -D option hangs while trying to destroy trace

[fazlin ahamed]

Ok i ll try out with 2.6.31 and let you know the results.. But the prob is i
would have to make it working for 2.6.29 anyway as it is the kernel tat we
ll be using (we have made few modifications in 2.6.29 to suit our needs)...

I debugged the problem more and here are my updates:

Once "lttctl -D -w /tmp/tdir/trace3 trace3" cmd hangs, i did ctrl+C to kill
the process.

After tat ps -aef shows two lttd process running. From the code i understood
tat one was started wen i started trace and other was started wen i issued
"lttctl -D" command.

And if i kill both these lttd process using "kill" command, i see lot of
"unread channel" messages in dmesg. I have pasted few below:

LTT : unread channel metadata offset is 262144 and cons_off : 0 (cpu 0)
LTT : metadata : commit count : 262144, subbuf size 262144
LTT : unread channel metadata offset is 262144 and cons_off : 0 (cpu 1)
LTT : metadata : commit count : 262144, subbuf size 262144
LTT : Tracing not active for trace trace1
LTT : unread channel metadata offset is 262144 and cons_off : 0 (cpu 0)
LTT : metadata : commit count : 262144, subbuf size 262144
LTT : unread channel metadata offset is 262144 and cons_off : 0 (cpu 1)
LTT : metadata : commit count : 262144, subbuf size 262144
LTT : unread channel metadata offset is 262144 and cons_off : 0 (cpu 0)
LTT : metadata : commit count : 262144, subbuf size 262144
LTT : unread channel metadata offset is 262144 and cons_off : 0 (cpu 1)
LTT : metadata : commit count : 262144, subbuf size 262144

My guess from the above msg was there are some trace data in buffers tat
couldnt be read to userspace since i killed "lttctl" and "lttd". Am i
guessing rite?

I also tried to run "lttd" by myself and i got the following error:

[root@(none) /]# /tmp/ltt/ltt-control-0.70-18082009/lttd/lttd -t
/tmp/tdir/trace2 -a -c /tmp/debugfs/ltt -v -d -n
Linux Trace Toolkit Trace Daemon 0.70-18082009

Reading from debugfs directory : /tmp/debugfs/ltt
Writing to trace directory : /tmp/tdir/trace2

Creating trace subdirectory /tmp/tdir/trace2
Adding inotify for channel /tmp/debugfs/ltt/
Added inotify for channel /tmp/debugfs/ltt/, wd 4294967295
Channel file : /tmp/debugfs/ltt/write_event
Opening file.
Appending to file /tmp/tdir/trace2/write_event as requested
Channel file : /tmp/debugfs/ltt/kprobes
Entering channel subdirectory...
Creating trace subdirectory /tmp/tdir/trace2/kprobes
Adding inotify for channel /tmp/debugfs/ltt/kprobes/
Added inotify for channel /tmp/debugfs/ltt/kprobes/, wd 4294967295
Channel file : /tmp/debugfs/ltt/kprobes/list
Opening file.
Appending to file /tmp/tdir/trace2/kprobes/list as requested
Channel file : /tmp/debugfs/ltt/kprobes/disable
Opening file.
...
...
...
Creating trace subdirectory /tmp/tdir/trace2/control
Adding inotify for channel /tmp/debugfs/ltt/control/
Added inotify for channel /tmp/debugfs/ltt/control/, wd 4294967295
Error in getting the number of subbuffers: Inappropriate ioctl for device

I am not sure whether these are related or valid. But my guess is
destroy_trace is sleeping/waiting for someone else (maybe lttd) and it is
not able to recover.

Is there any fix for this problem already in latest ltt-control or lttng
kernel patches??

Thanks in advance,
Fazlin

On Fri, Oct 30, 2009 at 7:36 PM, Mathieu Desnoyers <
compudj at krystal.dyndns.org> wrote:

> * fazlin ahamed (fazlincse at gmail.com) wrote:
> > Hi all,
> >
> > I am new to using lttng and previously i was using lttng in 2.6.18
> without
> > any problems. Now when i switched to 2.6.29, i downloaded the
> corresponding
> > patches (patch-2.6.29-lttng-0.121) and ltt-control tool
> > (ltt-control-0.70-18082009)..
> >
> > I patched the kernel and tried to start/stop tracing using following
> > commands:
> >
> > lttctl -C -w /tmp/tdir/trace3 -o channel.all.overwrite=1 trace3
> >
> > This command ran successfully. And wen i executed
> >
> > lttctl -D -w /tmp/tdir/trace3 trace3
> >
> > The cmd nevers returns... when i debugged further i found tat "write"
> call
> > to write trace3 to debugfs destroy_trace file hangs.
> >
> > Can anyone throw some light on this problem... forgive me if it is silly
> > question..
> >
>
> You might want to try with a newer LTTng version (for kernel 2.6.31) and
> see if you can reproduce the problem.
>
> Thanks,
>
> Mathieu
>
>
> > thanks in advance,
> > Fazlin
>
> > _______________________________________________
> > ltt-dev mailing list
> > ltt-dev at lists.casi.polymtl.ca
> > http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
>
>
> --
> Mathieu Desnoyers
> OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
>
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