[lttng-dev] Help debugging 2.2.0rc2 core dump in lttng-sessiond

Tue Jun 11 02:33:31 EDT 2013

Seems this only happens with --buffers-uid ...

Here's the sequence of activation I used:

/usr/bin/lttng-sessiond -d --no-kernel -q
/usr/bin/lttng create ${LTTNG_SESSION_NAME} -o ${LTTNG_TRACES_PATH}
/usr/bin/lttng enable-channel channel0 -u --subbuf-size 262144 
--num-subbuf 32 --buffers-uid
/usr/bin/lttng enable-event -u -a
/usr/bin/lttng start ${LTTNG_SESSION_NAME}

Amit Margalit
IBM XIV - Storage Reinvented
XIV-NAS Development Team
Tel. 03-689-7774
Fax. 03-689-7230

From:   Amit Margalit/Israel/IBM at IBMIL
To:     lttng-dev at lists.lttng.org
Date:   06/11/2013 08:32 AM
Subject:        [lttng-dev] Help debugging 2.2.0rc2 core dump in 
lttng-sessiond

Hello, 

I've deployed 2.2.0rc2 on one of our systems, and I've getting a core dump 
(due to segfault) on lttng-sessiond. 

Should I post all the data here, or should this be done 1x1 with one of 
the developers? 

Anyway, basic information: 

Core was generated by `/usr/bin/lttng-sessiond -d --no-kernel -q'. 
Program terminated with signal 11, Segmentation fault. 
#0  ustctl_duplicate_ust_object_data (dest=dest at entry=0x7f958c000ad8, 
src=0x0) at ustctl.c:800 
800             if (src->handle != -1) { 
(gdb) p *dest 
$9 = (struct lttng_ust_object_data *) 0x0 
(gdb) up 
#1  0x00000000004182c6 in duplicate_channel_object 
(ua_chan=0x7f958c0009b0, reg_chan=0x679cd0) at ust-app.c:2000 
2000            ret = ustctl_duplicate_ust_object_data(&ua_chan->obj, 
reg_chan->obj.ust); 
(gdb) p ua_chan->obj 
$10 = (struct lttng_ust_object_data *) 0x0 
(gdb) p *ua_chan 
$11 = {enabled = 1, handle = -1, is_sent = 0, key = 2, tracing_channel_id 
= 0, expected_stream_count = 0, name = "channel0", '\000' <repeats 247 
times>, obj = 0x0, attr = { 
    type = LTTNG_UST_CHAN_PER_CPU, subbuf_size = 262144, num_subbuf = 32, 
overwrite = 0, switch_timer_interval = 0, read_timer_interval = 0, output 
= LTTNG_UST_MMAP, chan_id = 0, 
    uuid = '\000' <repeats 15 times>}, streams = {count = 0, head = {next 
= 0x7f958c000b20, prev = 0x7f958c000b20}}, session = 0x677320, ctx = 
0x7f958c000bc0, events = 0x7f958c000920, 
  tracefile_size = 0, tracefile_count = 0, node = {key = 0x7f958c0009d4 
"channel0", node = {next = 0x6763a0, reverse_hash = 261524217965576192}, 
head = {next = {next = 0x0}, func = 0}}, 
  ust_objd_node = {key = 0, node = {next = 0x0, reverse_hash = 0}, head = 
{next = {next = 0x0}, func = 0}}, rcu_head = {next = {next = 0x0}, func = 
0}} 
(gdb) p *reg_chan 
$12 = {key = 0, consumer_key = 1, streams = {next = 0x679ce0, prev = 
0x679ce0}, stream_list_lock = {__data = {__lock = 0, __count = 0, __owner 
= 0, __nusers = 0, __kind = 0, __spins = 0, 
      __list = {__prev = 0x0, __next = 0x0}}, __size = '\000' <repeats 39 
times>, __align = 0}, node = {key = 0, node = {next = 0x0, reverse_hash = 
15577886586086949907}, head = {next = { 
        next = 0x0}, func = 0}}, obj = {ust = 0x0}} 
(gdb) bt 
#0  ustctl_duplicate_ust_object_data (dest=dest at entry=0x7f958c000ad8, 
src=0x0) at ustctl.c:800 
#1  0x00000000004182c6 in duplicate_channel_object 
(ua_chan=0x7f958c0009b0, reg_chan=0x679cd0) at ust-app.c:2000 
#2  send_channel_uid_to_ust (reg_chan=reg_chan at entry=0x679cd0, 
app=app at entry=0x664d00, ua_sess=ua_sess at entry=0x677320, 
ua_chan=ua_chan at entry=0x7f958c0009b0) at ust-app.c:2161 
#3  0x0000000000418f78 in create_channel_per_uid (ua_chan=0x7f958c0009b0, 
ua_sess=0x677320, usess=<optimized out>, app=0x664d00) at ust-app.c:2263 
#4  do_create_channel (app=app at entry=0x664d00, usess=usess at entry=0x666f80, 
ua_sess=0x677320, ua_chan=ua_chan at entry=0x7f958c0009b0) at ust-app.c:2341 
#5  0x000000000041df83 in ust_app_global_update (usess=0x666f80, 
sock=sock at entry=20) at ust-app.c:4043 
#6  0x000000000042306f in update_ust_app (app_sock=20) at main.c:680 
#7  thread_dispatch_ust_registration (data=<optimized out>) at main.c:1465 

#8  0x00007f95974dd5f0 in start_thread () from /lib64/libpthread.so.0 
#9  0x00007f959724c87d in clone () from /lib64/libc.so.6 
#10 0x0000000000000000 in ?? () 
(gdb) info threads 
  Id   Target Id         Frame 
  9    Thread 0x7f9594357710 (LWP 967) 0x00007f959724cf03 in epoll_wait () 
from /lib64/libc.so.6 
  8    Thread 0x7f9594558710 (LWP 966) 0x00007f959724cf03 in epoll_wait () 
from /lib64/libc.so.6 
  7    Thread 0x7f9593b53710 (LWP 971) 0x00007f959724cf03 in epoll_wait () 
from /lib64/libc.so.6 
  6    Thread 0x7f9593f55710 (LWP 969) 0x00007f959724cf03 in epoll_wait () 
from /lib64/libc.so.6 
  5    Thread 0x7f9598d85900 (LWP 964) 0x00007f95974ddda5 in pthread_join 
() from /lib64/libpthread.so.0 
  4    Thread 0x7f9593952710 (LWP 984) 0x00007f959724cf03 in epoll_wait () 
from /lib64/libc.so.6 
  3    Thread 0x7f9593751710 (LWP 3941) 0x00007f95972492a9 in syscall () 
from /lib64/libc.so.6 
  2    Thread 0x7f9593d54710 (LWP 970) 0x00007f959724cf03 in epoll_wait () 
from /lib64/libc.so.6 
* 1    Thread 0x7f9594156710 (LWP 968) ustctl_duplicate_ust_object_data 
(dest=dest at entry=0x7f958c000ad8, src=0x0) at ustctl.c:800 

Any help is appreciated. 

Amit Margalit 
IBM XIV - Storage Reinvented 
XIV-NAS Development Team 
Tel. 03-689-7774 
Fax. 03-689-7230_______________________________________________
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