[ltt-dev] Kernel Oops during lttctl_start()
Bernd.Hufmann at ericsson.com
Thu Apr 21 07:47:30 EDT 2011
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.
On 04/18/2011 10:12 PM, Mathieu Desnoyers wrote:
> * Mathieu Desnoyers (compudj at krystal.dyndns.org) wrote:
>> * Bernd Hufmann (Bernd.Hufmann at ericsson.com) 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 ?
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