Re: [PATCH 0/2] [GIT PULL] tracing: various bug fixes

From: Frederic Weisbecker
Date: Wed Apr 22 2009 - 07:48:14 EST

On Wed, Apr 22, 2009 at 02:48:09AM -0400, Steven Rostedt wrote:
>
>
> On Tue, 21 Apr 2009, Ingo Molnar wrote:
>
> >
> > * Ingo Molnar <mingo@xxxxxxx> wrote:
> >
> > > Pulled, thanks guys! I've reactivated the self-tests in tip:master
> > > - lets see how it goes today.
> >
> > i'm still getting a ring-buffer warning - see below. Config
> > attached.
> >
> > Ingo
> >
> > [ 7.671145] calling clear_boot_tracer+0x0/0x52 @ 1
> > [ 7.672145] initcall clear_boot_tracer+0x0/0x52 returned 0 after 0 usecs
> > [ 7.673145] calling event_trace_self_tests_init+0x0/0x5f @ 1
> > [ 7.674206] Running tests on trace events:
> > [ 7.675143] Testing event kfree_skb: OK
> > [ 7.680145] Testing event kmalloc: OK
> > [ 7.683819] Testing event kmem_cache_alloc: OK
> > [ 7.686755] Testing event kmalloc_node: OK
> > [ 7.689744] Testing event kmem_cache_alloc_node: OK
> > [ 7.692711] Testing event kfree: OK
> > [ 7.695712] Testing event kmem_cache_free: OK
> > [ 7.698744] Testing event irq_handler_exit: OK
> > [ 7.701724] Testing event irq_handler_entry: OK
> > [ 7.704710] Testing event softirq_entry: OK
> > [ 7.707743] Testing event softirq_exit: OK
> > [ 7.710768] Testing event lock_acquired: OK
> > [ 7.713738] Testing event lock_acquire: OK
> > [ 7.716782] Testing event lock_release: OK
> > [ 7.719771] Testing event lock_contended: OK
> > [ 7.722740] Testing event sched_kthread_stop: OK
> > [ 7.726741] Testing event sched_kthread_stop_ret: OK
> > [ 7.729710] Testing event sched_wait_task: OK
> > [ 7.732706] Testing event sched_wakeup: OK
> > [ 7.735713] Testing event sched_wakeup_new: OK
> > [ 7.738727] Testing event sched_switch: OK
> > [ 7.741724] Testing event sched_migrate_task: OK
> > [ 7.745711] Testing event sched_process_free: OK
> > [ 7.749704] Testing event sched_process_exit: OK
> > [ 7.753699] Testing event sched_process_wait: OK
> > [ 7.757692] Testing event sched_process_fork: OK
> > [ 7.761711] Testing event sched_signal_send: OK
> > [ 7.764709] Running tests on trace event systems:
> > [ 7.765144] Testing event system skb: OK
> > [ 7.768776] Testing event system kmem: OK
> > [ 7.771817] Testing event system irq: OK
> > [ 7.774778] Testing event system lockdep: OK
> > [ 7.777921] Testing event system sched: OK
> > [ 7.780902] Running tests on all trace events:
> > [ 7.781148] Testing all events: OK
> > [ 7.787765] Running tests again, along with the function tracer
> > [ 7.788156] Running tests on trace events:
> > [ 7.789154] Testing event kfree_skb: OK
> > [ 7.792858] Testing event kmalloc: OK
> > [ 7.795853] Testing event kmem_cache_alloc: OK
> > [ 7.799848] Testing event kmalloc_node: OK
> > [ 7.802966] Testing event kmem_cache_alloc_node: OK
> > [ 7.805970] Testing event kfree: OK
> > [ 7.808942] Testing event kmem_cache_free: OK
> > [ 7.812935] Testing event irq_handler_exit: OK
> > [ 7.815850] Testing event irq_handler_entry: OK
> > [ 7.818877] Testing event softirq_entry: OK
> > [ 7.822846] Testing event softirq_exit: OK
> > [ 7.825895] Testing event lock_acquired: OK
> > [ 7.830045] Testing event lock_acquire: OK
> > [ 7.834025] Testing event lock_release: OK
> > [ 7.837920] Testing event lock_contended: OK
> > [ 7.841854] Testing event sched_kthread_stop: OK
> > [ 7.844883] Testing event sched_kthread_stop_ret: OK
> > [ 7.847850] Testing event sched_wait_task: OK
> > [ 7.851938] Testing event sched_wakeup: OK
> > [ 7.855960] Testing event sched_wakeup_new: OK
> > [ 7.858884] Testing event sched_switch: OK
> > [ 7.861941] Testing event sched_migrate_task: OK
> > [ 7.864972] Testing event sched_process_free: OK
> > [ 7.867853] Testing event sched_process_exit: OK
> > [ 7.870890] Testing event sched_process_wait: OK
> > [ 7.873856] Testing event sched_process_fork: OK
> > [ 7.876930] Testing event sched_signal_send: OK
> > [ 7.879853] Running tests on trace event systems:
> > [ 7.880154] Testing event system skb: OK
> > [ 7.883940] Testing event system kmem: OK
> > [ 7.888105] Testing event system irq: OK
> > [ 7.892085] Testing event system lockdep: OK
> > [ 7.896154] Testing event system sched: OK
> > [ 7.901156] Running tests on all trace events:
> > [ 7.903170] Testing all events: <4>------------[ cut here ]------------
> > [ 7.909137] WARNING: at kernel/trace/ring_buffer.c:1245 __rb_reserve_next+0x130/0x40c()
> > [ 7.909137] Modules linked in:
> > [ 7.909137] Pid: 0, comm: swapper Not tainted 2.6.30-rc2-tip #38087
> > [ 7.909137] Call Trace:
> > [ 7.909137] <IRQ> [<ffffffff8025a273>] warn_slowpath+0xca/0x115
> > [ 7.909137] [<ffffffff802bf4fe>] ? __rb_reserve_next+0x2a5/0x40c
> > [ 7.909137] [<ffffffff8021ab74>] ? native_sched_clock+0x4f/0x6a
> > [ 7.909137] [<ffffffff8021ab74>] ? native_sched_clock+0x4f/0x6a
> > [ 7.909137] [<ffffffff8021ab74>] ? native_sched_clock+0x4f/0x6a
> > [ 7.909137] [<ffffffff802bf2c6>] ? __rb_reserve_next+0x6d/0x40c
> > [ 7.909137] [<ffffffff802cb54e>] ? time_hardirqs_off+0x31/0x47
> > [ 7.909137] [<ffffffff802bf389>] __rb_reserve_next+0x130/0x40c
> > [ 7.909137] [<ffffffff802c00ad>] rb_reserve_next_event+0x1d3/0x31a
> > [ 7.909137] [<ffffffff802c04c9>] ring_buffer_lock_reserve+0x16b/0x1cb
> > [ 7.909137] [<ffffffff802c4f4b>] trace_buffer_lock_reserve+0x34/0x7e
> > [ 7.909137] [<ffffffff802c542c>] trace_vbprintk+0x136/0x275
> > [ 7.909137] [<ffffffff8028534f>] ? trace_hardirqs_on_caller+0x132/0x18e
> > [ 7.909137] [<ffffffff80286cfb>] ? lock_acquire+0x74/0x15b
> > [ 7.909137] [<ffffffff802ca54b>] __trace_bprintk+0x80/0x9d
> > [ 7.909137] [<ffffffff802661bc>] ? run_timer_softirq+0x16f/0x281
> > [ 7.909137] [<ffffffff802ca54b>] ? __trace_bprintk+0x80/0x9d
> > [ 7.909137] [<ffffffff80283871>] ? put_lock_stats+0x44/0x5a
> > [ 7.909137] [<ffffffff802c5d68>] ? tracing_record_cmdline+0x3d/0x141
> > [ 7.909137] [<ffffffff802661bc>] ? run_timer_softirq+0x16f/0x281
> > [ 7.909137] [<ffffffff8028259c>] ftrace_event_lock_acquire+0x6a/0x89
> > [ 7.909137] [<ffffffff80266273>] ? run_timer_softirq+0x226/0x281
> > [ 7.909137] [<ffffffff80286cfb>] lock_acquire+0x74/0x15b
> > [ 7.909137] [<ffffffff80266273>] ? run_timer_softirq+0x226/0x281
> > [ 7.909137] [<ffffffff802668c1>] ? process_timeout+0x0/0x37
> > [ 7.909137] [<ffffffff80a246af>] _spin_lock_irq+0x5c/0xa5
> > [ 7.909137] [<ffffffff80266273>] ? run_timer_softirq+0x226/0x281
> > [ 7.909137] [<ffffffff80266273>] run_timer_softirq+0x226/0x281
> > [ 7.909137] [<ffffffff802661bc>] ? run_timer_softirq+0x16f/0x281
> > [ 7.909137] [<ffffffff802133d6>] ? ftrace_call+0x5/0x2b
> > [ 7.909137] [<ffffffff80260bd3>] __do_softirq+0xff/0x22c
> > [ 7.909137] [<ffffffff802149bc>] call_softirq+0x1c/0x30
> > [ 7.909137] [<ffffffff802163df>] do_softirq+0x5f/0xdb
> > [ 7.909137] [<ffffffff802601ac>] irq_exit+0x5d/0x7d
> > [ 7.909137] [<ffffffff80a2a076>] do_IRQ+0xbe/0xeb
> > [ 7.909137] [<ffffffff80214153>] ret_from_intr+0x0/0x16
> > [ 7.909137] <EOI> [<ffffffff802bf2a9>] ? __rb_reserve_next+0x50/0x40c
> > [ 7.909137] [<ffffffff802c00ad>] ? rb_reserve_next_event+0x1d3/0x31a
> > [ 7.909137] [<ffffffff802c00ad>] ? rb_reserve_next_event+0x1d3/0x31a
> > [ 7.909137] [<ffffffff802c04c9>] ? ring_buffer_lock_reserve+0x16b/0x1cb
> > [ 7.909137] [<ffffffff802c4f4b>] ? trace_buffer_lock_reserve+0x34/0x7e
> > [ 7.909137] [<ffffffff8021b722>] ? test_ti_thread_flag+0x8/0x38
> > [ 7.909137] [<ffffffff802c5d15>] ? trace_current_buffer_lock_reserve+0x36/0x4c
> > [ 7.909137] [<ffffffff802d3227>] ? function_test_events_call+0x8f/0x12e
> > [ 7.909137] [<ffffffff8021b841>] ? need_resched+0x36/0x54
> > [ 7.909137] [<ffffffff802d3251>] ? function_test_events_call+0xb9/0x12e
> > [ 7.909137] [<ffffffff802133d6>] ? ftrace_call+0x5/0x2b
> > [ 7.909137] [<ffffffff8021b727>] ? test_ti_thread_flag+0xd/0x38
> > [ 7.909137] [<ffffffff8021b841>] ? need_resched+0x36/0x54
> > [ 7.909137] [<ffffffff8021b945>] ? poll_idle+0x41/0x64
> > [ 7.909137] [<ffffffff802cb871>] ? stop_critical_timings+0x3d/0x54
> > [ 7.909137] [<ffffffff802127b2>] ? cpu_idle+0xb1/0x112
> > [ 7.909137] [<ffffffff809e6369>] ? rest_init+0x8d/0xa3
> > [ 7.909137] [<ffffffff8108709a>] ? start_kernel+0x49c/0x4bd
> > [ 7.909137] [<ffffffff81086140>] ? early_idt_handler+0x0/0x71
> > [ 7.909137] [<ffffffff810862ce>] ? x86_64_start_reservations+0xb9/0xd4
> > [ 7.909137] [<ffffffff81086000>] ? _sinittext+0x0/0x140
> > [ 7.909137] [<ffffffff81086441>] ? x86_64_start_kernel+0x158/0x17b
> > [ 7.909137] ---[ end trace 3b85485e39bcb7cf ]---
> > [ 7.912099] OK
> > [ 7.913421] initcall event_trace_self_tests_init+0x0/0x5f returned 0 after 233398 usecs
> > [ 7.914172] calling random32_reseed+0x0/0xce @ 1
> > [ 7.915159] initcall random32_reseed+0x0/0xce returned 0 after 0 usecs
> > [ 7.916145] calling pci_resource_alignment_sysfs_init+0x0/0x40 @ 1
> >
>
> I spent the entire day (and half the night) debugging this. I was fighting
> a case where the hardirqs_enabled flag in the task struct (lockdep flag)
> was mysteriously being set and cleared. I stepped through the entire
> kernel thread fork process (that was an exercise) and could not find
> anything wrong.
>
> Sometimes it would go away with printk's sometimes it would not. This was
> driving me crazy, until I noticed that paravirt was enabled.
>
> Turning off paravirtualization here (so far) makes everything run
> smoothly.
>
> Thus my theory is that there's something fishy with the modifying of the
> irq enable/disable code when the system detects that it is running on bare
> hardware.
>
> I'm too tired to look at this more. Ingo supplied a config to play with.
> You can disable VSMP too and it will still trigger the crash.
>
> -- Steve
>

It's indeed a tricky one. I can reproduce it too, I will
try to manage having an irqsoff trace at this point, hopefully I
could get the source of this irq disabling...

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