From mboxrd@z Thu Jan 1 00:00:00 1970 From: mathieu.desnoyers@efficios.com (Mathieu Desnoyers) Date: Thu, 23 Apr 2015 19:26:40 +0000 (UTC) Subject: [lttng-dev] [BUG] lttng-sessiond In-Reply-To: <3E06425C-5C41-4BF7-8156-A62C4E9B5E60@mailbox.tu-dresden.de> References: <3E06425C-5C41-4BF7-8156-A62C4E9B5E60@mailbox.tu-dresden.de> Message-ID: <1230298824.35208.1429817200877.JavaMail.zimbra@efficios.com> ----- Original Message ----- > Hello, > > I'm using LTTng with a kernel that has lock debugging enabled. I > familiarized myself with LTTng using the "Hello world" example, where > I encountered two bugs. Hi Hannes, Can you share with us the code of your "hello" probe ? Which version or git commit of lttng-modules are you using ? Thanks, Mathieu > > 1) Using multiple probes for the lttng-sessiond arguments > --kmod-probes and --extra-kmod-probes does not work: > > $ sudo lttng-sessiond --kmod-probes="hello,sched" -vvv > [...] > DEBUG1 - 11:54:22.413830 [17827/17827]: Modprobe successfully > lttng-probe-sched (in modprobe_lttng() at modprobe.c:285) > sh: 1: Syntax error: "(" unexpected > DEBUG1 - 11:54:22.415273 [17827/17827]: Unable to load optional module > (null); continuing (in modprobe_lttng() at modprobe.c:281) > [...] > > $ sudo lttng-sessiond --kmod-probes="sched,hello" -vvv > [...] > DEBUG1 - 11:55:13.879976 [17896/17896]: Modprobe successfully > lttng-probe-hello (in modprobe_lttng() at modprobe.c:285) > sh: 1: Syntax error: "(" unexpected > DEBUG1 - 11:55:13.881183 [17896/17896]: Unable to load optional module > (null); continuing (in modprobe_lttng() at modprobe.c:281) > [...] > > $ sudo lttng-sessiond --extra-kmod-probes="sched,hello" -vvv > [...] > DEBUG1 - 11:55:54.244515 [17966/17966]: Modprobe successfully > lttng-probe-hello (in modprobe_lttng() at modprobe.c:285) > sh: 1: Syntax error: "(" unexpected > DEBUG1 - 11:55:54.245758 [17966/17966]: Unable to load optional module > (null); continuing (in modprobe_lttng() at modprobe.c:281) > [...] > > It seems, only the last argument (module) is loaded correctly. > > 2) Having lttng-sessiond started: > $ sudo lttng-sessiond --kmod-probes=hello > And the tracer configured: > lttng create > lttng enable-event hello_world -k > > 'lttng start' causes a locking failure to be reported: > [ 159.783420] > [ 159.783922] ===================================== > [ 159.784067] [ BUG: bad unlock balance detected! ] > [ 159.784067] 4.0.0-rc4-atlas+ #200 Tainted: G O > [ 159.784067] ------------------------------------- > [ 159.784067] lttng-sessiond/1441 is trying to release lock (sessions_mutex) > at: > [ 159.784067] [] mutex_unlock+0xe/0x10 > [ 159.784067] but there are no more locks to release! > [ 159.784067] > [ 159.784067] other info that might help us debug this: > [ 159.784067] no locks held by lttng-sessiond/1441. > [ 159.784067] > [ 159.784067] stack backtrace: > [ 159.784067] CPU: 0 PID: 1441 Comm: lttng-sessiond Tainted: G O > 4.0.0-rc4-atlas+ #200 > [ 159.784067] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > Bochs 01/01/2011 > [ 159.784067] ffffffff81808c3e ffff88005d24fa28 ffffffff818029e0 > 0000000000000007 > [ 159.784067] ffff880057c9cd60 ffff88005d24fa58 ffffffff810c1924 > ffff88005d24fad8 > [ 159.784067] ffff880057c9cd60 ffffffffa01ce070 ffffffff81808c3e > ffff88005d24fa98 > [ 159.784067] Call Trace: > [ 159.784067] [] ? mutex_unlock+0xe/0x10 > [ 159.784067] [] dump_stack+0x4c/0x65 > [ 159.784067] [] print_unlock_imbalance_bug+0xf4/0x100 > [ 159.784067] [] ? mutex_unlock+0xe/0x10 > [ 159.784067] [] lock_release+0x2e6/0x460 > [ 159.784067] [] __mutex_unlock_slowpath+0x76/0x190 > [ 159.784067] [] mutex_unlock+0xe/0x10 > [ 159.784067] [] lttng_session_enable+0x208/0x5b0 > [lttng_tracer] > [ 159.784067] [] lttng_session_ioctl+0x155/0x300 > [lttng_tracer] > [ 159.784067] [] ? __lock_acquire+0x570/0x1f60 > [ 159.784067] [] ? sched_clock_local+0x25/0x90 > [ 159.784067] [] ? do_wp_page+0x3a7/0x900 > [ 159.784067] [] ? sched_clock_cpu+0x98/0xc0 > [ 159.784067] [] ? local_clock+0x15/0x30 > [ 159.784067] [] ? sched_clock_local+0x25/0x90 > [ 159.784067] [] ? do_wp_page+0x3a7/0x900 > [ 159.784067] [] ? __lock_acquire+0x570/0x1f60 > [ 159.784067] [] ? do_wp_page+0x3a7/0x900 > [ 159.784067] [] ? handle_mm_fault+0x310/0x18b0 > [ 159.784067] [] ? sched_clock_local+0x25/0x90 > [ 159.784067] [] ? sched_clock_local+0x25/0x90 > [ 159.784067] [] ? __fget+0x111/0x260 > [ 159.784067] [] ? sched_clock_cpu+0x98/0xc0 > [ 159.784067] [] ? local_clock+0x15/0x30 > [ 159.784067] [] ? __fget+0x111/0x260 > [ 159.784067] [] do_vfs_ioctl+0x308/0x560 > [ 159.784067] [] ? __fget+0x5/0x260 > [ 159.784067] [] ? __do_page_fault+0x1f1/0x4c0 > [ 159.784067] [] SyS_ioctl+0x81/0xa0 > [ 159.784067] [] system_call_fastpath+0x16/0x1b > > I hope this helps. > > -- > Best regards, > Hannes > > _______________________________________________ > lttng-dev mailing list > lttng-dev at lists.lttng.org > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com