From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bernd.Hufmann@ericsson.com (Bernd Hufmann) Date: Thu, 21 Apr 2011 07:47:30 -0400 Subject: [ltt-dev] Kernel Oops during lttctl_start() In-Reply-To: References: <4DAC4506.5050705@ericsson.com> Message-ID: <4DB01952.3090106@ericsson.com> 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 (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 >>> - 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: [] 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 >