* Ingo Molnar <mingo@elte.hu> wrote:

> very nice! I'd expect breakages and complications too so i 
> restructured tip/tracing/* a bit: firstly i created a tip/tracing/core 
> append-only merge branch which collects all the known-robust bits. 
> Then i created a new branch for your new generic ring-buffer feature: 
> tip/tracing/ring-buffer, and applied your patches. I've started 
> testing it.

-tip testing found that tip/tracing/ring-buffer causes a new lockdep 
splat:

[    0.000000] Linux version 2.6.27-rc8-tip-00915-g8cb18a9-dirty (mingo@dione)
               (gcc version 4.2.3) #37501 SMP Tue Sep 30 10:10:10 CEST 2008
[...]
[    0.268001] calling  tracer_alloc_buffers+0x0/0x1e5 @ 1
[    0.270983] ------------[ cut here ]------------
[    0.271100] WARNING: at kernel/lockdep.c:2880 check_flags+0x63/0x179()
[    0.271219] Modules linked in:
[    0.271356] Pid: 1, comm: swapper Not tainted 2.6.27-rc8-tip-00915-g8cb18a9-dirty #37501
[    0.271563] Call Trace:
[    0.271678]  [<ffffffff80271d2b>] warn_on_slowpath+0x5d/0x84
[    0.271797]  [<ffffffff80295973>] ? __lock_acquire+0xba4/0xbc5
[    0.271916]  [<ffffffff8029266d>] ? __raw_spin_is_locked+0x17/0x1a
[    0.272001]  [<ffffffff802929cc>] ? graph_unlock+0x79/0x7e
[    0.272001]  [<ffffffff8029449f>] ? mark_lock+0x1c/0x361
[    0.272001]  [<ffffffff8029483a>] ? mark_held_locks+0x56/0x71
[    0.272001]  [<ffffffff802cbb77>] ? time_hardirqs_off+0x12/0x26
[    0.272001]  [<ffffffff802934f1>] ? trace_hardirqs_off_caller+0x21/0xc2
[    0.272001]  [<ffffffff802927c3>] check_flags+0x63/0x179
[    0.272001]  [<ffffffff802966a1>] lock_acquire+0x51/0xc2
[    0.272001]  [<ffffffff816fcead>] _spin_lock+0x36/0x65
[    0.272001]  [<ffffffff802c7511>] ? ring_buffer_reset_cpu+0x47/0x6b
[    0.272001]  [<ffffffff802c7511>] ring_buffer_reset_cpu+0x47/0x6b
[    0.272001]  [<ffffffff802ca33f>] tracing_reset+0xc/0xe
[    0.272001]  [<ffffffff802cd0b4>] boot_trace_init+0x2a/0x46
[    0.272001]  [<ffffffff826817c3>] tracer_alloc_buffers+0x1a7/0x1e5
[    0.272001]  [<ffffffff8268161c>] ? tracer_alloc_buffers+0x0/0x1e5
[    0.272001]  [<ffffffff8020a062>] do_one_initcall+0x62/0x165
[    0.272001]  [<ffffffff816f3291>] ? print_cpu_info+0xab/0x135
[    0.272001]  [<ffffffff8024d8aa>] ? get_apic_id+0x0/0x13
[    0.272001]  [<ffffffff8268161c>] ? tracer_alloc_buffers+0x0/0x1e5
[    0.272001]  [<ffffffff8266190c>] kernel_init+0x60/0x21a
[    0.272001]  [<ffffffff8022daf9>] child_rip+0xa/0x11
[    0.272001]  [<ffffffff8022cc83>] ? restore_args+0x0/0x30
[    0.272001]  [<ffffffff802c5d03>] ? ftrace_convert_nops+0x25/0xb0
[    0.272001]  [<ffffffff8023362a>] ? sched_clock+0x17/0x1a
[    0.272001]  [<ffffffff826618ac>] ? kernel_init+0x0/0x21a
[    0.272001]  [<ffffffff8022daef>] ? child_rip+0x0/0x11
[    0.272001] ---[ end trace a7919e7f17c0a725 ]---
[    0.272001] possible reason: unannotated irqs-off.
[    0.272001] irq event stamp: 9069
[    0.272001] hardirqs last  enabled at (9069): [<ffffffff802949bf>] trace_hardirqs_on+0xd/0xf
[    0.272001] hardirqs last disabled at (9068): [<ffffffff8029359f>] trace_hardirqs_off+0xd/0xf
[    0.272001] softirqs last  enabled at (4082): [<ffffffff802773c3>] __do_softirq+0xe0/0xed
[    0.272001] softirqs last disabled at (4075): [<ffffffff8022dfec>] call_softirq+0x1c/0x28
[    0.272010] initcall tracer_alloc_buffers+0x0/0x1e5 returned 0 after 7 msecs
[    0.272409] lockdep: fixing up alternatives.
[    0.272604] Booting processor 1 APIC 0x1 ip 0x6000
[    0.004000] Initializing CPU#1

on a 64-bit allyesconfig bootup. Config attached.

The box booted up fine otherwise, so i'll continue testing the new code, 
to find other problems (if any).

	Ingo