[lttng-dev] [BUG] lttng-sessiond
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Thu Apr 23 16:13:29 EDT 2015
----- Original Message -----
> ----- 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 ?
I think the two issues should be fixed by this new
git commit in lttng-modules master branch:
commit 66fd8d5e4a6080f1b2db0f525c26c07e5b723aab
Author: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
Date: Thu Apr 23 16:11:15 2015 -0400
Fix: double-unlock of session mutex
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
Can you give it a try ?
Thanks!
Mathieu
>
> 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] [<ffffffff81808c3e>] 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] [<ffffffff81808c3e>] ? mutex_unlock+0xe/0x10
> > [ 159.784067] [<ffffffff818029e0>] dump_stack+0x4c/0x65
> > [ 159.784067] [<ffffffff810c1924>] print_unlock_imbalance_bug+0xf4/0x100
> > [ 159.784067] [<ffffffff81808c3e>] ? mutex_unlock+0xe/0x10
> > [ 159.784067] [<ffffffff810c6986>] lock_release+0x2e6/0x460
> > [ 159.784067] [<ffffffff81808b16>] __mutex_unlock_slowpath+0x76/0x190
> > [ 159.784067] [<ffffffff81808c3e>] mutex_unlock+0xe/0x10
> > [ 159.784067] [<ffffffffa00bcc98>] lttng_session_enable+0x208/0x5b0
> > [lttng_tracer]
> > [ 159.784067] [<ffffffffa00bdd75>] lttng_session_ioctl+0x155/0x300
> > [lttng_tracer]
> > [ 159.784067] [<ffffffff810c3a80>] ? __lock_acquire+0x570/0x1f60
> > [ 159.784067] [<ffffffff8109d095>] ? sched_clock_local+0x25/0x90
> > [ 159.784067] [<ffffffff811d41c7>] ? do_wp_page+0x3a7/0x900
> > [ 159.784067] [<ffffffff8109d2d8>] ? sched_clock_cpu+0x98/0xc0
> > [ 159.784067] [<ffffffff8109d355>] ? local_clock+0x15/0x30
> > [ 159.784067] [<ffffffff8109d095>] ? sched_clock_local+0x25/0x90
> > [ 159.784067] [<ffffffff811d41c7>] ? do_wp_page+0x3a7/0x900
> > [ 159.784067] [<ffffffff810c3a80>] ? __lock_acquire+0x570/0x1f60
> > [ 159.784067] [<ffffffff811d41c7>] ? do_wp_page+0x3a7/0x900
> > [ 159.784067] [<ffffffff811d5820>] ? handle_mm_fault+0x310/0x18b0
> > [ 159.784067] [<ffffffff8109d095>] ? sched_clock_local+0x25/0x90
> > [ 159.784067] [<ffffffff8109d095>] ? sched_clock_local+0x25/0x90
> > [ 159.784067] [<ffffffff81248e41>] ? __fget+0x111/0x260
> > [ 159.784067] [<ffffffff8109d2d8>] ? sched_clock_cpu+0x98/0xc0
> > [ 159.784067] [<ffffffff8109d355>] ? local_clock+0x15/0x30
> > [ 159.784067] [<ffffffff81248e41>] ? __fget+0x111/0x260
> > [ 159.784067] [<ffffffff8123c998>] do_vfs_ioctl+0x308/0x560
> > [ 159.784067] [<ffffffff81248d35>] ? __fget+0x5/0x260
> > [ 159.784067] [<ffffffff8104f201>] ? __do_page_fault+0x1f1/0x4c0
> > [ 159.784067] [<ffffffff8123cc71>] SyS_ioctl+0x81/0xa0
> > [ 159.784067] [<ffffffff8180cfb6>] 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
>
> _______________________________________________
> 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
More information about the lttng-dev
mailing list