On Tue, May 11, 2010 at 11:11:20AM -0400, Mathieu Desnoyers wrote:
> * [email protected] ([email protected]) wrote:
> > Thanks Mathieu. I'm going to have to look at this a bit more. This may
> > have fixed one problem and cause another as "lttctl -C -w /tmp/trace
> > trace1" does not return and I'm getting a stack dump in the messages
> > file (see below). The last msg I see from that "lttctl -C" command is
> > "lttctl: Creating trace". The "lttctl: Forking lttd" is not displayed.
>
> If you disable RCU stalls detection, does it work ?
>
> [Context for Paul: it's on a -RT kernel, with the LTTng patchset]
Strange. It looks like everyone is idle.
Or is it possible that some CPU is spinning in an NMI handler?
You have six call traces -- are there six CPUs online?
Thanx, Paul
> Thanks,
>
> Mathieu
>
> >
> > JP
> >
> > May 11 10:05:00 ans-ebb3 kernel: P5
> > May 11 10:05:00 ans-ebb3 kernel: INFO: RCU detected CPU stalls: P5
> > (detected by 0, t=10002 jiffies)
> > May 11 10:05:00 ans-ebb3 kernel: sending NMI to all CPUs:
> > May 11 10:05:00 ans-ebb3 kernel: NMI backtrace for cpu 1
> > May 11 10:05:00 ans-ebb3 kernel: Modules linked in: battery sbshc ehci_hcd
> > sbs scsi_dh ohci_hcd dm_multipath uhci_hcd scsi_mod dm_mirror sd_mod libata
> > ahci dm_mod dm_log dm_region_hash tpm_bios tpm intel_agp
> > iTCO_vendor_support i2c_core pcspkr tpm_tis iTCO_wdt i2c_i801 autofs4
> > e1000e button serio_raw sg output video ac parport lp parport_pc ipv6
> > nvidia(P) [last unloaded: nvidia]
> > May 11 10:05:00 ans-ebb3 kernel:
> > May 11 10:05:00 ans-ebb3 kernel: Pid: 0, comm: swapper Tainted: P
> > 2.6.33.2-rt13.11.trace #10 PXT /To Be Filled By O.E.M.
> > May 11 10:05:00 ans-ebb3 kernel: EIP: 0060:[<c062e4fa>] EFLAGS: 00000246
> > CPU: 1
> > May 11 10:05:00 ans-ebb3 kernel: EIP is at poll_idle+0x1e/0x5c
> > May 11 10:05:00 ans-ebb3 kernel: EAX: f74bc000 EBX: 6b655cfc ECX: 6b655cfc
> > EDX: 000001a2
> > May 11 10:05:00 ans-ebb3 kernel: ESI: 000001a2 EDI: 00000000 EBP: f74bcf84
> > ESP: f74bcf7c
> > May 11 10:05:00 ans-ebb3 kernel: DS: 007b ES: 007b FS: 00d8 GS: 0000 SS:
> > 0068 preempt:04010002
> > May 11 10:05:00 ans-ebb3 kernel: Process swapper (pid: 0, ti=f74bc000
> > task=f74d90c0 task.ti=f74bc000)
> > May 11 10:05:00 ans-ebb3 kernel: Stack:
> > May 11 10:05:00 ans-ebb3 kernel: f765b02c f765b01c f74bcf94 c062e7c9
> > 00000001 c0877c90 f74bcfa4 c0401c0d
> > May 11 10:05:00 ans-ebb3 kernel: <0> 00000001 00000000 f74bcfb0 c06ca177
> > 01020800 00000000 00000000 00000000
> > May 11 10:05:00 ans-ebb3 kernel: <0> 00000000 00000000 00000000 00000000
> > 00000000 00000000 00000000 000000d8
> > May 11 10:05:00 ans-ebb3 kernel: Call Trace:
> > May 11 10:05:00 ans-ebb3 kernel: [<c062e7c9>] ? cpuidle_idle_call+0x6c/0xdf
> > May 11 10:05:00 ans-ebb3 kernel: [<c0401c0d>] ? cpu_idle+0x49/0x80
> > May 11 10:05:00 ans-ebb3 kernel: [<c06ca177>] ? start_secondary+0x1b9/0x1be
> > May 11 10:05:00 ans-ebb3 kernel: Code: ff ff ff 8d 65 f4 89 d8 5b 5e 5f 5d
> > c3 55 89 e5 56 53 e8 7b 61 e2 ff 89 c3 89 d6 fb 89 e0 25 00 f0 ff ff eb 02
> > f3 90 f6 40 08 08 <74> f8 e8 60 61 e2 ff 29 d8 19 f2 e8 95 b6 e0 ff b9 40
> > 42 0f 00
> > May 11 10:05:00 ans-ebb3 kernel: Call Trace:
> > May 11 10:05:00 ans-ebb3 kernel: [<c062e7c9>] cpuidle_idle_call+0x6c/0xdf
> > May 11 10:05:00 ans-ebb3 kernel: [<c0401c0d>] cpu_idle+0x49/0x80
> > May 11 10:05:00 ans-ebb3 kernel: [<c06ca177>] start_secondary+0x1b9/0x1be
> > May 11 10:05:00 ans-ebb3 kernel: Pid: 0, comm: swapper Tainted: P
> > 2.6.33.2-rt13.11.trace #10
> > May 11 10:05:00 ans-ebb3 kernel: Call Trace:
> > May 11 10:05:00 ans-ebb3 kernel: [<c04019d4>] ? show_regs+0x1a/0x20
> > May 11 10:05:00 ans-ebb3 kernel: [<c06d0d7a>] nmi_watchdog_tick+0x9b/0x162
> > May 11 10:05:00 ans-ebb3 kernel: [<c06d02e1>] do_nmi+0xd1/0x2e1
> > May 11 10:05:00 ans-ebb3 kernel: [<c056355d>] ?
> > ltt_chan_for_each_channel+0x35/0x4f
> > May 11 10:05:00 ans-ebb3 kernel: [<c05628df>] ?
> > ltt_chanbuf_idle_switch+0x0/0x1c
> > May 11 10:05:00 ans-ebb3 kernel: [<c06cfd41>] nmi_stack_correct+0x28/0x2d
> > May 11 10:05:00 ans-ebb3 kernel: [<c062e4fa>] ? poll_idle+0x1e/0x5c
> > May 11 10:05:00 ans-ebb3 kernel: [<c062e7c9>] cpuidle_idle_call+0x6c/0xdf
> > May 11 10:05:00 ans-ebb3 kernel: [<c0401c0d>] cpu_idle+0x49/0x80
> > May 11 10:05:00 ans-ebb3 kernel: [<c06ca177>] start_secondary+0x1b9/0x1be
> > May 11 10:05:00 ans-ebb3 kernel: NMI backtrace for cpu 0
> > May 11 10:05:00 ans-ebb3 kernel: Modules linked in: battery sbshc ehci_hcd
> > sbs scsi_dh ohci_hcd dm_multipath uhci_hcd scsi_mod dm_mirror sd_mod libata
> > ahci dm_mod dm_log dm_region_hash tpm_bios tpm intel_agp
> > iTCO_vendor_support i2c_core pcspkr tpm_tis iTCO_wdt i2c_i801 autofs4
> > e1000e button serio_raw sg output video ac parport lp parport_pc ipv6
> > nvidia(P) [last unloaded: nvidia]
> > May 11 10:05:00 ans-ebb3 kernel:
> > May 11 10:05:00 ans-ebb3 kernel: Pid: 0, comm: swapper Tainted: P
> > 2.6.33.2-rt13.11.trace #10 PXT /To Be Filled By O.E.M.
> > May 11 10:05:00 ans-ebb3 kernel: EIP: 0060:[<c0570ab6>] EFLAGS: 00000807
> > CPU: 0
> > May 11 10:05:00 ans-ebb3 kernel: EIP is at delay_tsc+0x0/0x8a
> > May 11 10:05:00 ans-ebb3 kernel: EAX: 001c7b29 EBX: 00000001 ECX: 04f29000
> > EDX: 001c7b28
> > May 11 10:05:00 ans-ebb3 kernel: ESI: 00000000 EDI: c084a6c0 EBP: c0828e6c
> > ESP: c0828e68
> > May 11 10:05:00 ans-ebb3 kernel: DS: 007b ES: 007b FS: 00d8 GS: 0000 SS:
> > 0068 preempt:04020002
> > May 11 10:05:00 ans-ebb3 kernel: Process swapper (pid: 0, ti=c0828000
> > task=c08407a0 task.ti=c0828000)
> > May 11 10:05:00 ans-ebb3 kernel: Stack:
> > May 11 10:05:00 ans-ebb3 kernel: c0570a4f c0828e78 c0418e84 c084a740
> > c0828eb0 c047c35b c07c1944 00000000
> > May 11 10:05:00 ans-ebb3 kernel: <0> 00002712 c5805268 c084a6c0 c084a6ec
> > 00000003 c084a740 00000083 00000000
> > May 11 10:05:00 ans-ebb3 kernel: <0> 00000000 c08407a0 c0828ec0 c047c45f
> > 00000000 00000000 c0828ed4 c0441fbd
> > May 11 10:05:00 ans-ebb3 kernel: Call Trace:
> > May 11 10:05:00 ans-ebb3 kernel: [<c0570a4f>] ? __const_udelay+0x2f/0x31
> > May 11 10:05:01 ans-ebb3 kernel: [<c0418e84>] ?
> > arch_trigger_all_cpu_backtrace+0x42/0x4f
> > May 11 10:05:01 ans-ebb3 kernel: [<c047c35b>] ? __rcu_pending+0x258/0x309
> > May 11 10:05:01 ans-ebb3 kernel: [<c047c45f>] ?
> > rcu_check_callbacks+0x53/0x114
> > May 11 10:05:01 ans-ebb3 kernel: [<c0441fbd>] ?
> > update_process_times+0x32/0x43
> > May 11 10:05:01 ans-ebb3 kernel: [<c04587b7>] ? tick_sched_timer+0x6d/0x9b
> > May 11 10:05:01 ans-ebb3 kernel: [<c045874a>] ? tick_sched_timer+0x0/0x9b
> > May 11 10:05:01 ans-ebb3 kernel: [<c044f8fc>] ? __run_hrtimer+0xeb/0x154
> > May 11 10:05:01 ans-ebb3 kernel: [<c044fc4d>] ?
> > hrtimer_interrupt+0xed/0x21e
> > May 11 10:05:01 ans-ebb3 kernel: [<c04518c5>] ?
> > sched_clock_idle_wakeup_event+0x16/0x18
> > May 11 10:05:01 ans-ebb3 kernel: [<c0418512>] ?
> > smp_apic_timer_interrupt+0xb4/0x106
> > May 11 10:05:01 ans-ebb3 kernel: [<c06cfa66>] ?
> > apic_timer_interrupt+0x2a/0x30
> > May 11 10:05:01 ans-ebb3 kernel: [<c062e4f6>] ? poll_idle+0x1a/0x5c
> > May 11 10:05:01 ans-ebb3 kernel: [<c062e7c9>] ? cpuidle_idle_call+0x6c/0xdf
> > May 11 10:05:01 ans-ebb3 kernel: [<c0401c0d>] ? cpu_idle+0x49/0x80
> > May 11 10:05:01 ans-ebb3 kernel: [<c06bdde4>] ? rest_init+0x80/0x82
> > May 11 10:05:01 ans-ebb3 kernel: [<c087a859>] ? start_kernel+0x2fb/0x300
> > May 11 10:05:01 ans-ebb3 kernel: [<c087a08c>] ? i386_start_kernel+0x8c/0x91
> > May 11 10:05:01 ans-ebb3 kernel: Code: c0 8b 0c 8d 18 7b 87 c0 6b c0 14 ba
> > 40 ff 8d c0 55 89 e5 69 94 0a 98 00 00 00 fa 00 00 00 f7 e2 8d 42 01 ff 15
> > 90 84 85 c0 5d c3 <55> 89 e5 57 56 89 c6 53 83 ec 04 89 e0 25 00 f0 ff ff
> > ff 40 14
> > May 11 10:05:01 ans-ebb3 kernel: Call Trace:
> > May 11 10:05:01 ans-ebb3 kernel: [<c0570a4f>] ? __const_udelay+0x2f/0x31
> > May 11 10:05:01 ans-ebb3 kernel: [<c0418e84>]
> > arch_trigger_all_cpu_backtrace+0x42/0x4f
> > May 11 10:05:01 ans-ebb3 kernel: [<c047c35b>] __rcu_pending+0x258/0x309
> > May 11 10:05:01 ans-ebb3 kernel: [<c047c45f>]
> > rcu_check_callbacks+0x53/0x114
> > May 11 10:05:01 ans-ebb3 kernel: [<c0441fbd>]
> > update_process_times+0x32/0x43
> > May 11 10:05:01 ans-ebb3 kernel: [<c04587b7>] tick_sched_timer+0x6d/0x9b
> > May 11 10:05:01 ans-ebb3 kernel: [<c045874a>] ? tick_sched_timer+0x0/0x9b
> > May 11 10:05:01 ans-ebb3 kernel: [<c044f8fc>] __run_hrtimer+0xeb/0x154
> > May 11 10:05:01 ans-ebb3 kernel: [<c044fc4d>] hrtimer_interrupt+0xed/0x21e
> > May 11 10:05:01 ans-ebb3 kernel: [<c04518c5>] ?
> > sched_clock_idle_wakeup_event+0x16/0x18
> > May 11 10:05:01 ans-ebb3 kernel: [<c0418512>]
> > smp_apic_timer_interrupt+0xb4/0x106
> > May 11 10:05:01 ans-ebb3 kernel: [<c06cfa66>]
> > apic_timer_interrupt+0x2a/0x30
> > May 11 10:05:01 ans-ebb3 kernel: [<c062e4f6>] ? poll_idle+0x1a/0x5c
> > May 11 10:05:01 ans-ebb3 kernel: [<c062e7c9>] cpuidle_idle_call+0x6c/0xdf
> > May 11 10:05:01 ans-ebb3 kernel: [<c0401c0d>] cpu_idle+0x49/0x80
> > May 11 10:05:01 ans-ebb3 kernel: [<c06bdde4>] rest_init+0x80/0x82
> > May 11 10:05:01 ans-ebb3 kernel: [<c087a859>] start_kernel+0x2fb/0x300
> > May 11 10:05:01 ans-ebb3 kernel: [<c087a08c>] i386_start_kernel+0x8c/0x91
> > May 11 10:05:01 ans-ebb3 kernel: Pid: 0, comm: swapper Tainted: P
> > 2.6.33.2-rt13.11.trace #10
> > May 11 10:05:01 ans-ebb3 kernel: Call Trace:
> > May 11 10:05:01 ans-ebb3 kernel: [<c04019d4>] ? show_regs+0x1a/0x20
> > May 11 10:05:01 ans-ebb3 kernel: [<c06d0d7a>] nmi_watchdog_tick+0x9b/0x162
> > May 11 10:05:01 ans-ebb3 kernel: [<c06d02e1>] do_nmi+0xd1/0x2e1
> > May 11 10:05:01 ans-ebb3 kernel: [<c05645a8>] ? ltt_vtrace+0x0/0x79b
> > May 11 10:05:02 ans-ebb3 kernel: [<c06cfd41>] nmi_stack_correct+0x28/0x2d
> > May 11 10:05:02 ans-ebb3 kernel: [<c0570ab6>] ? delay_tsc+0x0/0x8a
> > May 11 10:05:02 ans-ebb3 kernel: [<c0570a4f>] ? __const_udelay+0x2f/0x31
> > May 11 10:05:02 ans-ebb3 kernel: [<c0418e84>]
> > arch_trigger_all_cpu_backtrace+0x42/0x4f
> > May 11 10:05:02 ans-ebb3 kernel: [<c047c35b>] __rcu_pending+0x258/0x309
> > May 11 10:05:02 ans-ebb3 kernel: [<c047c45f>]
> > rcu_check_callbacks+0x53/0x114
> > May 11 10:05:02 ans-ebb3 kernel: [<c0441fbd>]
> > update_process_times+0x32/0x43
> > May 11 10:05:02 ans-ebb3 kernel: [<c04587b7>] tick_sched_timer+0x6d/0x9b
> > May 11 10:05:02 ans-ebb3 kernel: [<c045874a>] ? tick_sched_timer+0x0/0x9b
> > May 11 10:05:02 ans-ebb3 kernel: [<c044f8fc>] __run_hrtimer+0xeb/0x154
> > May 11 10:05:02 ans-ebb3 kernel: [<c044fc4d>] hrtimer_interrupt+0xed/0x21e
> > May 11 10:05:02 ans-ebb3 kernel: [<c04518c5>] ?
> > sched_clock_idle_wakeup_event+0x16/0x18
> > May 11 10:05:02 ans-ebb3 kernel: [<c0418512>]
> > smp_apic_timer_interrupt+0xb4/0x106
> > May 11 10:05:02 ans-ebb3 kernel: [<c06cfa66>]
> > apic_timer_interrupt+0x2a/0x30
> > May 11 10:05:02 ans-ebb3 kernel: [<c062e4f6>] ? poll_idle+0x1a/0x5c
> > May 11 10:05:02 ans-ebb3 kernel: [<c062e7c9>] cpuidle_idle_call+0x6c/0xdf
> > May 11 10:05:02 ans-ebb3 kernel: [<c0401c0d>] cpu_idle+0x49/0x80
> > May 11 10:05:02 ans-ebb3 kernel: [<c06bdde4>] rest_init+0x80/0x82
> > May 11 10:05:02 ans-ebb3 kernel: [<c087a859>] start_kernel+0x2fb/0x300
> > May 11 10:05:02 ans-ebb3 kernel: [<c087a08c>] i386_start_kernel+0x8c/0x91
> >
> >
> >
> > -----Original Message-----
> > From: Mathieu Desnoyers [mailto:[email protected]]
> > Sent: Tue 5/11/2010 7:59 AM
> > To: John P. Paul
> > Cc: [email protected]
> > Subject: Re: [ltt-dev] lttctl locks up with RT Linux
> >
> > * [email protected] ([email protected]) wrote:
> > > Hey Mathieu:
> > >
> > > Thanks for looking at this. I'm a bit new to debugging at this level, so
> > > you may need to provide me a bit more info on what you need. I attempted
> > > to use "pstack" on the lttctl and lttd tasks ... no luck as pstack also
> > > locked up.
> > >
> > > I put a bit of tracing into liblttctl and discovered the lockup occurs
> > > when a write of "traceName" (whatever traceName happens to be) occurs to
> > > the "/mnt/debugfs/ltt/destroy_trace" file.
> > >
> > > I'm guessing that you would like some tracing of the ltt kernel module.
> > > Is there something that I can turn on, or another way I could get a
> > > stack dump of that module after lockup? I'll do a little research this
> > > weekend on kernel debugging techniques.
> > >
> > > I can certainly sprinkle in some printk statements in the ltt kernel
> > > module source. Doing provided the following info:
> > >
> > > - Control entered _ltt_trace_destroy (single underscore)
> > > - Control entered del_timer_sync(<t_async_wakeup_timer) and never
> > > returned
> > >
> > > Does that help, or should I continue farther down this path?
> >
> > Can you try the following patch to see if it fixes your problem ?
> >
> >
> > lttng fix rt kernel teardown deadlock
> >
> > LTTng has a teardown bug on RT (deadlock):
> >
> > Deleting a timer (sync) while holding the traces mutex, and the handler
> > takes
> > the same mutex, which leads to a deadlock.
> >
> > Fix this by taking a RCU read lock in the timer (instead of the RT-specific
> > fix
> > using the mutex), and by doing synchronize_rcu() in addition to
> > synchronize_sched() upon updates.
> >
> > Signed-off-by: Mathieu Desnoyers <[email protected]>
> > ---
> > ltt/ltt-tracer.c | 28 ++++++++++++++++++----------
> > 1 file changed, 18 insertions(+), 10 deletions(-)
> >
> > Index: linux-2.6-lttng/ltt/ltt-tracer.c
> > ===================================================================
> > --- linux-2.6-lttng.orig/ltt/ltt-tracer.c 2010-05-11 07:50:46.000000000
> > -0400
> > +++ linux-2.6-lttng/ltt/ltt-tracer.c 2010-05-11 07:55:46.000000000
> > -0400
> > @@ -41,6 +41,14 @@
> > #include <linux/vmalloc.h>
> > #include <asm/atomic.h>
> >
> > +static void synchronize_trace(void)
> > +{
> > + synchronize_sched();
> > +#ifdef CONFIG_PREEMPT_RT
> > + synchronize_rcu();
> > +#endif
> > +}
> > +
> > static void async_wakeup(unsigned long data);
> >
> > static DEFINE_TIMER(ltt_async_wakeup_timer, async_wakeup, 0, 0);
> > @@ -321,7 +329,7 @@ void ltt_module_unregister(enum ltt_modu
> > ltt_filter_unregister();
> > ltt_run_filter_owner = NULL;
> > /* Wait for preempt sections to finish */
> > - synchronize_sched();
> > + synchronize_trace();
> > break;
> > case LTT_FUNCTION_FILTER_CONTROL:
> > ltt_filter_control_functor = ltt_filter_control_default;
> > @@ -429,13 +437,13 @@ static void async_wakeup(unsigned long d
> > * PREEMPT_RT does not allow spinlocks to be taken within preempt
> > * disable sections (spinlock taken in wake_up). However, mainline won't
> > * allow mutex to be taken in interrupt context. Ugly.
> > - * A proper way to do this would be to turn the timer into a
> > - * periodically woken up thread, but it adds to the footprint.
> > + * Take a standard RCU read lock for RT kernels, which imply that we
> > + * also have to synchronize_rcu() upon updates.
> > */
> > #ifndef CONFIG_PREEMPT_RT
> > rcu_read_lock_sched();
> > #else
> > - ltt_lock_traces();
> > + rcu_read_lock();
> > #endif
> > list_for_each_entry_rcu(trace, <t_traces.head, list) {
> > trace_async_wakeup(trace);
> > @@ -443,7 +451,7 @@ static void async_wakeup(unsigned long d
> > #ifndef CONFIG_PREEMPT_RT
> > rcu_read_unlock_sched();
> > #else
> > - ltt_unlock_traces();
> > + rcu_read_unlock();
> > #endif
> >
> > mod_timer(<t_async_wakeup_timer, jiffies + LTT_PERCPU_TIMER_INTERVAL);
> > @@ -901,7 +909,7 @@ int ltt_trace_alloc(const char *trace_na
> > set_kernel_trace_flag_all_tasks();
> > }
> > list_add_rcu(&trace->list, <t_traces.head);
> > - synchronize_sched();
> > + synchronize_trace();
> >
> > ltt_unlock_traces();
> >
> > @@ -974,7 +982,7 @@ static int _ltt_trace_destroy(struct ltt
> > }
> > /* Everything went fine */
> > list_del_rcu(&trace->list);
> > - synchronize_sched();
> > + synchronize_trace();
> > if (list_empty(<t_traces.head)) {
> > clear_kernel_trace_flag_all_tasks();
> > /*
> > @@ -1195,7 +1203,7 @@ static int _ltt_trace_stop(struct ltt_tr
> > trace->nr_channels);
> > trace->active = 0;
> > ltt_traces.num_active_traces--;
> > - synchronize_sched(); /* Wait for each tracing to be finished */
> > + synchronize_trace(); /* Wait for each tracing to be finished */
> > }
> > module_put(ltt_run_filter_owner);
> > /* Everything went fine */
> > @@ -1327,12 +1335,12 @@ static void __exit ltt_exit(void)
> > list_for_each_entry_rcu(trace, <t_traces.head, list)
> > _ltt_trace_stop(trace);
> > /* Wait for quiescent state. Readers have preemption disabled. */
> > - synchronize_sched();
> > + synchronize_trace();
> > /* Safe iteration is now permitted. It does not have to be RCU-safe
> > * because no readers are left. */
> > list_for_each_safe(pos, n, <t_traces.head) {
> > trace = container_of(pos, struct ltt_trace, list);
> > - /* _ltt_trace_destroy does a synchronize_sched() */
> > + /* _ltt_trace_destroy does a synchronize_trace() */
> > _ltt_trace_destroy(trace);
> > __ltt_trace_destroy(trace);
> > }
> >
> >
> >
> > --
> > This is an e-mail from General Dynamics Robotic Systems. It is for the
> > intended recipient only and may contain confidential and privileged
> > information. No one else may read, print, store, copy, forward or act in
> > reliance on it or its attachments. If you are not the intended recipient,
> > please return this message to the sender and delete the message and any
> > attachments from your computer. Your cooperation is appreciated.
> >
>
> --
> Mathieu Desnoyers
> Operating System Efficiency R&D Consultant
> EfficiOS Inc.
> http://www.efficios.com
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