Hrm, after double-check, there was an ancient bug (dating from lttng 0.x) in lttng-statedump. Can you try with the last fix pushed into stable-2.0, stable-2.1, master ?
commit c3cd3de91a64e9f786e11658b1d05440e496352f Author: Mathieu Desnoyers <[email protected]> Date: Wed Jan 9 12:40:55 2013 -0500 Fix: statedump hang/too early completion due to logic error The previous "Fix: statedump hang due to incorrect wait/wakeup use" was not actually fixing the real problem. The issue is that we should pass the expected condition to wait_event() rather than its contrary. This bug has been sitting there for a while. I suspect that a recent change in the Linux scheduler behavior for newly spawned worker threads might have contributed to trigger the hang more reliably. The effects of this bugs are: - possible hang of the lttng-sessiond (within the kernel) at tracing start, - the statedump end event is traced before all worker threads have actually completed, which can confuse LTTng viewer state systems. Reported-by: Phil Wilshire <[email protected]> Signed-off-by: Mathieu Desnoyers <[email protected]> Thanks, Mathieu * Mathieu Desnoyers ([email protected]) wrote: > Hi Phil, > > I pushed a fix into master, stable-2.1, and stable-2.0 branches of > lttng-modules that fixes the issue you reported. Please confirm if it > fixes things for you. > > The fix: > > commit 8240b2e21a7ce1653d5e45b01c4709c86c3fb636 > Author: Mathieu Desnoyers <[email protected]> > Date: Tue Jan 8 14:27:05 2013 -0500 > > Fix: statedump hang due to incorrect wait/wakeup use > > Reported-by: Phil Wilshire <[email protected]> > Signed-off-by: Mathieu Desnoyers <[email protected]> > > Thanks, > > Mathieu > > * Mathieu Desnoyers ([email protected]) wrote: > > * Mathieu Desnoyers ([email protected]) wrote: > > > * Phil Wilshire ([email protected]) wrote: > > > > Hi, > > > > Just getting back into lttng after quite a few years > > > > I need to set up a continuous trace on a system. > > > > > > > > Every 10 seconds I stop one session and start another to give me > > > > individual > > > > files for each 10 second segment. > > > > I originally intended to start the next session before stopping the > > > > previous but that was causing the sessond to hang. > > > > > > > > Ever so often I can start the trace and the trace file is generated but > > > > ongoing commands to lttng are ignored. The new trace file then grows > > > > until > > > > all the disk space is used. sessiond seems to be hung > > > > > > > > > > > > I have the kernel dmseg log attached and I also have the trace file if > > > > needed > > > > > > > > > > > > [ 345.223564] LTT state dump thread start > > > > [ 345.231033] LTT state dump end > > > > [ 353.586011] ring buffer relay-metadata: 3604 records written, 0 > > > > records > > > > overrun > > > > [ 353.590023] ring buffer relay-discard, cpu 0: 408474 records > > > > written, 0 > > > > records overrun > > > > [ 353.590237] ring buffer relay-discard, cpu 1: 390793 records > > > > written, 0 > > > > records overrun > > > > [ 353.590237] ring buffer relay-discard, cpu 2: 363560 records > > > > written, 0 > > > > records overrun > > > > [ 353.590685] ring buffer relay-discard, cpu 3: 518867 records > > > > written, 0 > > > > records overrun > > > > [ 355.720753] LTTng: state dump begin > > > > [ 355.720753] LTT state dump thread start > > > > [ 355.732034] LTT state dump end > > > > [ 364.111388] ring buffer relay-metadata: 3604 records written, 0 > > > > records > > > > overrun > > > > [ 364.120334] ring buffer relay-discard, cpu 0: 409693 records > > > > written, 0 > > > > records overrun > > > > [ 364.120334] ring buffer relay-discard, cpu 1: 401971 records > > > > written, 0 > > > > records overrun > > > > [ 364.121438] ring buffer relay-discard, cpu 2: 380074 records > > > > written, 0 > > > > records overrun > > > > [ 364.122187] ring buffer relay-discard, cpu 3: 524538 records > > > > written, 0 > > > > records overrun > > > > [ 366.259690] LTTng: state dump begin > > > > [ 366.259690] LTT state dump thread start > > > > [ 366.266253] LTT state dump end > > > > [ 374.633764] ring buffer relay-metadata: 3604 records written, 0 > > > > records > > > > overrun > > > > [ 374.640024] ring buffer relay-discard, cpu 0: 430919 records > > > > written, 0 > > > > records overrun > > > > [ 374.640024] ring buffer relay-discard, cpu 1: 387021 records > > > > written, 0 > > > > records overrun > > > > [ 374.641033] ring buffer relay-discard, cpu 2: 370007 records > > > > written, 0 > > > > records overrun > > > > [ 374.641033] ring buffer relay-discard, cpu 3: 528606 records > > > > written, 0 > > > > records overrun > > > > [ 376.795384] LTTng: state dump begin > > > > [ 376.795384] LTT state dump thread start > > > > [ 601.060274] INFO: task lttng-sessiond:2885 blocked for more than 120 > > > > seconds. > > > > [ 601.069038] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" > > > > disables > > > > this message. > > > > [ 601.077626] lttng-sessiond D ffff880074456b18 0 2885 1 > > > > 0x10000000 > > > > [ 601.085210] ffff88006c0679f8 0000000000000082 0000000000000001 > > > > ffff88007b0a4140 > > > > [ 601.094031] ffff88006c0679a8 ffff880074456840 ffff88006c067fd8 > > > > ffff88006c067fd8 > > > > [ 601.105026] 0000000000011c80 ffff880074456840 0000000000000000 > > > > ffff88006c067a68 > > > > [ 601.112170] Call Trace: > > > > [ 601.116027] [<ffffffff812dd423>] schedule+0x5b/0x5d > > > > > > Hrm, the kernel seems to be stuck in the statedump. We added new stuff > > > there in LTTng-modules 2.1, so there is probably something fishy. > > > > > > This backtrace only tells us that the statedump is waiting for > > > do_lttng_statedump to complete. > > > > > > I would really like to see the backtrace of all tasks in your system at > > > that point (SysRQ t). For more info, see Documentation/sysrq.txt from > > > your Linux kernel sources. Also the dump of sysrq-l (all active cpus) > > > would be useful. Also sysrq-d (all locks held) might help. > > > > > > I've been able to reproduce the issue on my setup. More to come soon. > > > > Thanks, > > > > Mathieu > > > > > > > > More below, > > > > > > > [ 601.121025] [<ffffffffa01b46cb>] lttng_statedump_start+0x5aa/0x623 > > > > [lttng_statedump] > > > > [ 601.129035] [<ffffffff810543c7>] ? abort_exclusive_wait+0x8f/0x8f > > > > [ 601.136030] [<ffffffffa01c03bb>] lttng_session_enable+0x52d/0x55b > > > > [lttng_tracer] > > > > [ 601.144034] [<ffffffff810543c7>] ? abort_exclusive_wait+0x8f/0x8f > > > > [ 601.150039] [<ffffffffa01c0de8>] lttng_session_ioctl+0x15f/0x225 > > > > [lttng_tracer] > > > > [ 601.158042] [<ffffffff8123a1c3>] ? sock_recvmsg+0xa4/0xb9 > > > > [ 601.163185] [<ffffffff810f37b7>] ? lookup_page_cgroup+0x36/0x4d > > > > [ 601.169453] [<ffffffff81186cf9>] ? cpumask_any_but+0x29/0x38 > > > > [ 601.175508] [<ffffffff8109984b>] ? trace_preempt_on+0x12/0x2f > > > > [ 601.182031] [<ffffffff812e15eb>] ? sub_preempt_count+0x97/0xc0 > > > > [ 601.187735] [<ffffffff812de9a1>] ? _raw_spin_unlock+0x2a/0x35 > > > > [ 601.193922] [<ffffffff810c9767>] ? spin_unlock+0xe/0x10 > > > > [ 601.200027] [<ffffffff810caa44>] ? do_wp_page+0x26f/0x563 > > > > [ 601.206028] [<ffffffff8109987a>] ? trace_preempt_off+0x12/0x30 > > > > [ 601.212031] [<ffffffff812e16c8>] ? add_preempt_count+0xb4/0xcf > > > > [ 601.218043] [<ffffffff810cc320>] ? handle_pte_fault+0x6c6/0x76c > > > > [ 601.223737] [<ffffffff812443a7>] ? verify_iovec+0x52/0xa3 > > > > [ 601.229426] [<ffffffff810cc6cc>] ? handle_mm_fault+0x199/0x1a9 > > > > [ 601.236033] [<ffffffff812e14d3>] ? do_page_fault+0x2f6/0x377 > > > > [ 601.242034] [<ffffffffa01c4f8d>] ? > > > > __event_probe__sys_mprotect+0xf5/0xf5 [lttng_tracer] > > > > [ 601.251031] [<ffffffff8110332a>] vfs_ioctl+0x22/0x3a > > > > [ 601.256029] [<ffffffff81103bb7>] do_vfs_ioctl+0x3c4/0x407 > > > > [ 601.261188] [<ffffffff810f6e8e>] ? fget_light+0x91/0x9d > > > > [ 601.267026] [<ffffffff81103c41>] sys_ioctl+0x47/0x6a > > > > [ 601.272050] [<ffffffff812e377f>] tracesys+0xd9/0xde > > > > > > > > > > > > cat /proc/cpuinfo > > > > > > > > processor : 0 > > > > vendor_id : GenuineIntel > > > > cpu family : 6 > > > > model : 28 > > > > model name : Intel(R) Atom(TM) CPU D525 @ 1.80GHz > > > > stepping : 10 > > > > microcode : 0x107 > > > > cpu MHz : 1799.823 > > > > cache size : 512 KB > > > > physical id : 0 > > > > siblings : 4 > > > > core id : 0 > > > > cpu cores : 2 > > > > apicid : 0 > > > > initial apicid : 0 > > > > fpu : yes > > > > fpu_exception : yes > > > > cpuid level : 10 > > > > wp : yes > > > > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov > > > > pat > > > > pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm > > > > constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 > > > > monitor ds_cpl tm2 ssse3 cx16 xtpr pdcm movbe lahf_lm dts > > > > bogomips : 1775.61 > > > > clflush size : 64 > > > > cache_alignment : 64 > > > > address sizes : 36 bits physical, 48 bits virtual > > > > power management: > > > > > > > > (repeated for 3 other cpus ) > > > > > > > > uname -a > > > > Linux 3.2.21-x510v1 #1 SMP PREEMPT Thu Dec 20 11:24:36 EST 2012 x86_64 > > > > GNU/Linux > > > > > > > > Script used to run trace > > > > ================================================= > > > > #!/bin/sh > > > > > > > > xx=`/bin/date +"%s"` > > > > yy="yy" > > > > zz="zz" > > > > log_xx=/home/pswuser/trace/log/psw-${xx}.log > > > > log_yy=/home/pswuser/trace/log/psw-${yy}.log > > > > log_zz=/home/pswuser/trace/log/psw-${zz}.log > > > > #depmod > > > > mkdir -p /home/pswuser/trace > > > > mount -t tmpfs -o size=500M tmpfs /home/pswuser/trace > > > > mkdir -p /home/pswuser/trace/log > > > > touch /home/pswuser/trace/run_trace > > > > sleep 20 > > > > if [ -f /home/pswuser/trace/run_trace ] ; then > > > > > > > > echo "lttng create" > ${log_xx} > > > > lttng create psw-${xx} \ > > > > -o /home/pswuser/trace/psw-${xx} >> ${log_xx} 2>&1 > > > > echo "lttng enable-event" >> ${log_xx} > > > > sleep 1 > > > > lttng enable-event -a -k -s psw-${xx} >> ${log_xx} 2>&1 > > > > sleep 1 > > > > echo "lttng start" >> ${log_xx} > > > > lttng start psw-${xx} >> ${log_xx} 2>&1 > > > > sleep 1 > > > > > > > > fi > > > > > > > > while [ 1 -gt 0 ] ; do > > > > sleep 7 > > > > yy=`/bin/date +"%s"` > > > > log_yy=/home/pswuser/trace/log/psw-${yy}.log > > > > > > > > > > > > #stop xx > > > > if [ -d /home/pswuser/trace/psw-${xx} ] ; then > > > > echo "lttng stop" >> ${log_xx} > > > > lttng stop psw-${xx} >> ${log_xx} 2>&1 > > > > sleep 1 > > > > echo "lttng destroy" >> ${log_xx} > > > > lttng destroy psw-${xx} >> ${log_xx} 2>&1 > > > > echo "lttng done" >> ${log_xx} > > > > fi > > > > > > > > # start yy after stopping xx > > > > if [ -f /home/pswuser/trace/run_trace ] ; then > > > > echo "lttng create ${yy} after closing ${xx}" > ${log_yy} > > > > lttng create psw-${yy} \ > > > > -o /home/pswuser/trace/psw-${yy} >> ${log_yy} 2>&1 > > > > sleep 1 > > > > echo "lttng enable_event" >> ${log_yy} > > > > lttng enable-event -a -k -s psw-${yy} >> ${log_yy} 2>&1 > > > > sleep 1 > > > > echo "lttng start" >> ${log_yy} > > > > lttng start psw-${yy} >> ${log_yy} 2>&1 > > > > fi > > > > # check zz > > > > # delete unless detected or detected2 is present > > > > if [ ! -f /home/pswuser/bin/delay-detected ] && > > > > [ ! -f /home/pswuser/bin/delay-detected2 ] ; then > > > > echo "lttng delete files" >> ${log_zz} > > > > rm -rf /home/pswuser/trace/psw-${zz}* >> ${log_zz} 2>&1 > > > > #if [ $? -eq 0 ] ; then rm ${log_zz} ; fi > > > > fi > > > > # delete second snapshot > > > > if [ -f /home/pswuser/bin/delay-detected2 ] ; then > > > > rm -f /home/pswuser/bin/delay-detected2 > > > > > > > > # no more tracing once event detected > > > > rm -f /home/pswuser/trace/run_trace > > > > fi > > > > # trigger second snapshot delete first snapshot > > > > if [ -f /home/pswuser/bin/delay-detected ] ; then > > > > rm -f /home/pswuser/bin/delay-detected > > > > touch /home/pswuser/bin/delay-detected2 > > > > fi > > > > > > > > # ls -l /lttng-traces/psw-* > > > > # zz (delete candidate) is old xx > > > > echo "xx ${xx} yy ${yy} zz ${zz}" > > > > zz=${xx} > > > > log_zz=$log_xx > > > > > > > > # xx is now the new one > > > > xx=${yy} > > > > log_xx=$log_yy > > > > > > > > # check disk use > > > > if [ -d /home/pswuser/trace ] ; then > > > > du -h /home/pswuser/trace > > > > fi > > > > > > > > > > > > done > > > > ---------------------------------------- > > > > > > > > Any clues are welcome. > > > > > > > > Another question. > > > > > > > > Would it be possible to do this by setting up a ring buffer that will > > > > wrap > > > > around after a certain time. I can easily timestamp the event I am > > > > looking > > > > for and then capture the buffer containing the event. > > > > > > Stay tuned for 2013 lttng releases. This will likely be implemented this > > > year (flight recorder and snapshots). > > > > > > Thanks, > > > > > > Mathieu > > > > > > > > > > > > > > > Regards > > > > Phil Wilshire > > > > > > > _______________________________________________ > > > > lttng-dev mailing list > > > > [email protected] > > > > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > > > > > > > > > -- > > > Mathieu Desnoyers > > > Operating System Efficiency R&D Consultant > > > EfficiOS Inc. > > > http://www.efficios.com > > > > > > _______________________________________________ > > > lttng-dev mailing list > > > [email protected] > > > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > > > > -- > > Mathieu Desnoyers > > Operating System Efficiency R&D Consultant > > EfficiOS Inc. > > http://www.efficios.com > > > > _______________________________________________ > > lttng-dev mailing list > > [email protected] > > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > > -- > Mathieu Desnoyers > Operating System Efficiency R&D Consultant > EfficiOS Inc. > http://www.efficios.com > > _______________________________________________ > lttng-dev mailing list > [email protected] > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com _______________________________________________ lttng-dev mailing list [email protected] http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
