[lttng-dev] deadlock in ust baddr 2.4.0-rc1

[mathieu.desnoyers@efficios.com (Mathieu Desnoyers)]

Hi Paul,

We are facing a deadlock with the UST baddr feature in 2.4.0-rc1. Here is how to
reproduce:

Build UST ae5f44dbf46c87c1318fde8ab5b5a68048e5af08 by following doc/java-util-logging.txt
Build tools 077df0b372f77833c1de2dd9f534dec9e75696de

Install into system + run lttng-sessiond as user (there is an issue David is working
on that prevents non-root applications to register to the root session daemon, so
make sure sessiond is not run as root for now).

run doc/examples/java-jul  ./run file (in UST)

example output (all is OK, since no tracing is active):

24-Nov-2013 3:05:37 AM Hello main
INFO: Hello World, the answer is 42
Firing hello delay in 10 seconds...
24-Nov-2013 3:05:47 AM Hello main
INFO: Hello World delayed...
Cleaning Hello

Then start JUL tracing with:

lttng create
lttng enable-event -j -a
lttng start

./run


libust[3438/3439]: Error: Timed out waiting for lttng-sessiond (in lttng_ust_init() at lttng-ust-comm.c:1397)

even worse if:

LTTNG_UST_REGISTER_TIMEOUT=-1 ./run

The application deadlocks like this (on thread 2 in gdb):


(gdb) bt full
#0  __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:136
No locals.
#1  0x00007f78ce4c2354 in _L_lock_997 () from /lib/x86_64-linux-gnu/libpthread.so.0
No symbol table info available.
#2  0x00007f78ce4c21b7 in __pthread_mutex_lock (mutex=0x7f78ceb0c948) at pthread_mutex_lock.c:82
        ignore1 = <optimized out>
        ignore2 = <optimized out>
        ignore3 = <optimized out>
        __PRETTY_FUNCTION__ = "__pthread_mutex_lock"
        type = 3467692360
#3  0x00007f78ce8fdadb in ?? () from /lib64/ld-linux-x86-64.so.2
No symbol table info available.
#4  0x00007f78ce0b1f66 in dlopen_doit (a=<optimized out>) at dlopen.c:67
        args = 0x7f78c5903520
#5  0x00007f78ce8f9bd6 in ?? () from /lib64/ld-linux-x86-64.so.2
No symbol table info available.
#6  0x00007f78ce0b22ec in _dlerror_run (operate=0x7f78ce0b1f00 <dlopen_doit>, args=0x7f78c5903520) at dlerror.c:164
        result = 0x1568b30
#7  0x00007f78ce0b1ee1 in __dlopen (file=<optimized out>, mode=<optimized out>) at dlopen.c:88
        args = {file = 0x7f78c69a7eb9 "liblttng-ust-baddr.so.0", mode = 258, new = 0x101010101010101, caller = 0x7f78c696d8a9}
#8  0x00007f78c696d8a9 in lttng_ust_baddr_handle () at lttng-ust-comm.c:249
        __func__ = "lttng_ust_baddr_handle"
#9  0x00007f78c696d999 in lttng_ust_baddr_statedump (session=0x159ded0) at lttng-ust-comm.c:264
        baddr_handle = 0xc69a7dd7
        lttng_ust_baddr_init_fn = 0
        __func__ = "lttng_ust_baddr_statedump"
#10 0x00007f78c6971317 in ust_listener_thread (arg=0x7f78c6bbd000) at lttng-ust-comm.c:1254
        session = 0x159ded0
        len = 612
        lum = {handle = 1, cmd = 128, padding = '\000' <repeats 31 times>, u = {channel = {len = 0, type = LTTNG_UST_CHAN_PER_CPU, 
              padding = '\000' <repeats 287 times>, data = 0x7f78c5903d54 ""}, stream = {len = 0, stream_nr = 0, 
              padding = '\000' <repeats 287 times>}, event = {instrumentation = LTTNG_UST_TRACEPOINT, 
              name = '\000' <repeats 255 times>, loglevel_type = LTTNG_UST_LOGLEVEL_ALL, loglevel = 0, 
              padding = '\000' <repeats 15 times>, u = {padding = '\000' <repeats 287 times>}}, context = {
              ctx = LTTNG_UST_CONTEXT_VTID, padding = '\000' <repeats 15 times>, u = {padding = '\000' <repeats 287 times>}}, 
            version = {major = 0, minor = 0, patchlevel = 0}, tracepoint = {name = '\000' <repeats 255 times>, loglevel = 0, 
              padding = '\000' <repeats 15 times>}, filter = {data_size = 0, reloc_offset = 0, seqnum = 0}, exclusion = {
              count = 0}, padding = '\000' <repeats 31 times>}}
        sock_info = 0x7f78c6bbd000
        sock = 15
        ret = 0
        prev_connect_failed = 0
        has_waited = 0
        timeout = -1
        __func__ = "ust_listener_thread"
        __PRETTY_FUNCTION__ = "ust_listener_thread"
#11 0x00007f78ce4bfb50 in start_thread (arg=<optimized out>) at pthread_create.c:304
        __res = <optimized out>
        pd = 0x7f78c5904700
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {140156687369984, -4360901099104425548, 140156840281200, 140156687370688, 
                140156840493120, 3, 4434775346229094836, 4434756016842287540}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 
              0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = <optimized out>
        freesize = <optimized out>
        __PRETTY_FUNCTION__ = "start_thread"
#12 0x00007f78cde01a7d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112


It is deadlocked on the constructor awaiting for semaphore completion. The
mutex is probably the internal libc dynamic linker mutex held across
constructor execution:


#0  sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:86
No locals.
#1  0x00007f78c6971eb6 in lttng_ust_init () at lttng-ust-comm.c:1404
        constructor_timeout = {tv_sec = 140736647255400, tv_nsec = 5}
        sig_all_blocked = {__val = {18446744067267100671, 18446744073709551615 <repeats 15 times>}}
        orig_parent_mask = {__val = {4, 140156702215847, 1, 140156702215909, 140153372803072, 140156840282096, 0, 140156594940184, 
            140156840281472, 140156840281496, 3467478208, 140156840282096, 140156709124528, 140156707014326, 140156833869240, 
            140156840308736}}
        thread_attr = {
          __size = "\000\000\000\000\000\000\000\000\001\000\000\000\000\000\000\000\000\020", '\000' <repeats 37 times>, 
          __align = 0}
        timeout_mode = -1
        ret = 0
        __PRETTY_FUNCTION__ = "lttng_ust_init"
        __func__ = "lttng_ust_init"
#2  0x00007f78ce8f9f80 in ?? () from /lib64/ld-linux-x86-64.so.2
No symbol table info available.
#3  0x00007f78ce8fa077 in ?? () from /lib64/ld-linux-x86-64.so.2
No symbol table info available.
#4  0x00007f78ce8fe363 in ?? () from /lib64/ld-linux-x86-64.so.2
No symbol table info available.
#5  0x00007f78ce8f9bd6 in ?? () from /lib64/ld-linux-x86-64.so.2
No symbol table info available.
#6  0x00007f78ce8fdb4a in ?? () from /lib64/ld-linux-x86-64.so.2
No symbol table info available.
#7  0x00007f78ce0b1f66 in dlopen_doit (a=<optimized out>) at dlopen.c:67
        args = 0x7f78cead8b20
#8  0x00007f78ce8f9bd6 in ?? () from /lib64/ld-linux-x86-64.so.2
No symbol table info available.
#9  0x00007f78ce0b22ec in _dlerror_run (operate=0x7f78ce0b1f00 <dlopen_doit>, args=0x7f78cead8b20) at dlerror.c:164
        result = 0x14e2630
#10 0x00007f78ce0b1ee1 in __dlopen (file=<optimized out>, mode=<optimized out>) at dlopen.c:88
        args = {file = 0x7f78c00eb5f0 "/home/compudj/git/lttng-ust/liblttng-ust-jul/.libs/liblttng-ust-jul-jni.so.0.0.0", mode = 1, 
          new = 0x14ea800, caller = 0x7f78cd7abf9f}
#11 0x00007f78cd7abf9f in os::dll_load(char const*, char*, int) ()
   from /usr/lib/jvm/java-6-openjdk-amd64/jre/lib/amd64/server/libjvm.so
No symbol table info available.
#12 0x00007f78cd648f3f in JVM_LoadLibrary () from /usr/lib/jvm/java-6-openjdk-amd64/jre/lib/amd64/server/libjvm.so
No symbol table info available.
#13 0x00007f78cc3799f7 in Java_java_lang_ClassLoader_00024NativeLibrary_load ()
   from /usr/lib/jvm/java-6-openjdk-amd64/jre/lib/amd64/libjava.so
No symbol table info available.
#14 0x00007f78c8939d68 in ?? ()
No symbol table info available.
#15 0x00007f78cead95d0 in ?? ()
No symbol table info available.
#16 0x00007f78c892e85a in ?? ()
No symbol table info available.
#17 0x00007f78cead9580 in ?? ()
No symbol table info available.
#18 0x0000000000000000 in ?? ()
No symbol table info available.

So it looks like calling dlopen() from within lttng-ust is tricky, because it
introduces deadlocks with the dynamic linker.

Thoughts ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com