I found a very simple way to prevent the deadlock situation. Here again the jul sample that reproduces the issue:
pwoegere@atv-pwoegere-l3:~/MGC/lttng2_stack_latest/lttng-ust/doc/examples/java-jul> ./run libust[2876/2877]: Error: Timed out waiting for lttng-sessiond (in lttng_ust_init() at lttng-ust-comm.c:1400) Nov 25, 2013 1:07:36 PM Hello main INFO: Hello World, the answer is 42 Firing hello delay in 10 seconds... Nov 25, 2013 1:07:46 PM Hello main INFO: Hello World delayed... Cleaning Hello /home/pwoegere/MGC/lttng2_stack_latest/lttng-ust/doc/examples/java-jul By using *LD_PRELOAD* we are able to make sure that the critical dlopen turns into a null operation (thus the locking gets prevented): pwoegere@atv-pwoegere-l3:~/MGC/lttng2_stack_latest/lttng-ust/doc/examples/java-jul> *LD_PRELOAD=liblttng-ust-baddr.so.0 ./run* Nov 25, 2013 1:08:42 PM Hello main INFO: Hello World, the answer is 42 Firing hello delay in 10 seconds... Nov 25, 2013 1:08:52 PM Hello main INFO: Hello World delayed... Cleaning Hello /home/pwoegere/MGC/lttng2_stack_latest/lttng-ust/doc/examples/java-jul Do you want me to restructure the base-address-state tracing code to make the *LD_PRELOAD=liblttng-ust-baddr.so.0* approach the one and only way to use it ? Best, Paul On 11/25/2013 12:30 PM, Woegerer, Paul wrote: > Hi Mathieu, > Hi David, > > thanks for putting this together. > I'm now able to reproduce the problem and I'm investigating options to > circumvent the deadlock. > > I will keep you informed on any progress made. > > For the time being I will send a patch to prevent > lttng_ust_baddr_statedump if environment-variable > LTTNG_UST_WITHOUT_BADDR_STATEDUMP is set. This was already requested in > another context anyway. See: > http://lists.lttng.org/pipermail/lttng-dev/2013-November/021861.html > > -- > Thanks, > Paul > > > On 11/24/2013 09:13 AM, Mathieu Desnoyers wrote: >> 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 >> > -- Paul Woegerer, SW Development Engineer Sourcery Analyzer <http://go.mentor.com/sourceryanalyzer> Mentor Graphics, Embedded Software Division _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
