Hi Mathieu
Thank you very much for looking at the problem and for providing a fix.
Unfortunately, I won't be able to test the fix any time soon, because it
requires to compile and install a new kernel on my virtual machine which
can take some time. When it is integrated in a later LTTng PPA release
for Ubuntu I will be able to give it a try.
Best Regards
Bernd
On 04/18/2011 10:12 PM, Mathieu Desnoyers wrote:
* Mathieu Desnoyers ([email protected]) wrote:
* Bernd Hufmann ([email protected]) wrote:
[...]
Steps to reproduce:
- Enable all markers (use ltt-armall)
- Start tcf-client
- connect<remote>
- tcf ltt_control setupTrace "kernel" "0" "h2"
- tcf ltt_control setChannelEnable "kernel" "0" "h2" false
- tcf ltt_control allocTrace "kernel" "0" "h2"
- lttctl_client ltt_control writeTraceLocal "kernel" "0" "h2"
"/tmp/h2" 2 false false false
- tcf ltt_control startTrace "kernel" "0" "h2"
Now, the command startTrace won't return. It hangs on line "if
(write(fd, op, strlen(op)) == -1)" of method "lttctl_sendop()" which was
called by method "lttctl_start()" (see file liblttctrl.c). Please see
attached file "dmesg_start.log" for the dmesg output.
[...]
[ 416.740678] LTT : Tracing not active for trace h5
[ 416.740908] LTT state dump begin
[ 416.740931] LTT state dump thread start
[ 416.743693] LTT state dump end
[ 447.956279] LTT: 36 events written in channel metadata (cpu 0, index 0)
[ 447.956424] LTT: 54278 events written in channel fs (cpu 0, index 0)
[ 447.956468] LTT: 40989 events written in channel fs (cpu 0, index 1)
[ 618.382904] LTT : Tracing not active for trace h6
[ 618.383350] BUG: unable to handle kernel NULL pointer dereference at 00000014
[ 618.383983] IP: [<e080828f>] ltt_trace_start+0x7f/0x190 [ltt_tracer]
This looks like a bug in lttng-modules (the LTTng kernel modules).
Probably a bug with the way the current LTTng-stable versions handle the
trace session "templates". The good news is that we are getting rid of
all that code in the upcoming LTTng (with UST/ltt-sessiond/CTF
integration), so this bug is very likely to vanish then.
I'll try to have a look.
Thanks for reporting this.
It should be fixed in the lttng-modules.git tree v0.19-stable branch now
(commit e5b34c668a7d7b8aeab9fa2bdbb31eed4eff7929). Can you try again
using this version of lttng-modules and confirm that it fixes your crash
before I post a new lttng-modules v0.19-stable release ?
Thanks,
Mathieu
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