Hi Steven,

This warning occur from time to time in my tests:

[  593.080133] Testing tracer function: 
[  593.149895] ------------[ cut here ]------------
[  593.149895] WARNING: at /c/kernel-tests/src/stable/kernel/lockdep.c:3545 check_flags+0x1c8/0x1d0()
[  593.149895] Modules linked in:
[  593.149895] Pid: 1, comm: swapper/0 Not tainted 3.7.0-rc1-12129-gee2dd3c #3
[  593.149895] Call Trace:
[  593.149895]  <IRQ>  [<ffffffff810734cf>] warn_slowpath_common+0x8f/0xc0
[  593.149895]  [<ffffffff8107351a>] warn_slowpath_null+0x1a/0x20
[  593.149895]  [<ffffffff810fac08>] check_flags+0x1c8/0x1d0
[  593.149895]  [<ffffffff810fbfed>] lock_is_held+0x4d/0xa0
[  593.149895]  [<ffffffff8156d570>] ? notify_die+0x30/0x30
[  593.149895]  [<ffffffff81081b13>] ? __local_bh_enable+0x1d3/0x230
[  593.149895]  [<ffffffff81133cdf>] rcu_read_lock_held+0x7f/0x90
[  593.149895]  [<ffffffff81134208>] ftrace_ops_no_ops+0x188/0x190
[  593.149895]  [<ffffffff81573872>] trace+0x55/0x93
[  593.149895]  [<ffffffff81573872>] ? trace+0x55/0x93
[  593.149895]  [<ffffffff81566fc9>] ? _raw_spin_unlock_irq+0x99/0xc0
[  593.149895]  [<ffffffff8156d575>] ? sub_preempt_count+0x5/0x210
[  593.149895]  [<ffffffff8156d575>] ? sub_preempt_count+0x5/0x210
[  593.149895]  [<ffffffff81081b13>] ? __local_bh_enable+0x1d3/0x230
[  593.149895]  [<ffffffff810827ea>] __do_softirq+0x42a/0x710
[  593.149895]  [<ffffffff81574c7c>] call_softirq+0x1c/0x30
[  593.149895]  [<ffffffff81028a05>] do_softirq+0x1d5/0x2a0
[  593.149895]  [<ffffffff81082d3d>] irq_exit+0xad/0xc0
[  593.149895]  [<ffffffff81028035>] do_IRQ+0x75/0x100
[  593.149895]  [<ffffffff81567c72>] common_interrupt+0x72/0x72
[  593.149895]  <EOI>  [<ffffffff810fafbb>] ? mark_held_locks+0x9b/0x100
[  593.149895]  [<ffffffff815675f3>] ? _raw_spin_unlock_irqrestore+0xd3/0x130
[  593.149895]  [<ffffffff81307487>] __debug_object_init+0x1b7/0x580
[  593.149895]  [<ffffffff813078c6>] debug_object_init_on_stack+0x36/0x40
[  593.149895]  [<ffffffff8108a565>] init_timer_on_stack_key+0x35/0x80
[  593.149895]  [<ffffffff815616fb>] schedule_timeout+0x8b/0x470
[  593.149895]  [<ffffffff81573872>] ? trace+0x55/0x93
[  593.149895]  [<ffffffff81562fb7>] ? __mutex_unlock_slowpath+0x247/0x380
[  593.149895]  [<ffffffff81133487>] ? update_ftrace_function+0x17/0x150
[  593.149895]  [<ffffffff81561afe>] schedule_timeout_uninterruptible+0x1e/0x20
[  593.149895]  [<ffffffff8108ea60>] msleep+0x20/0x30
[  593.149895]  [<ffffffff81145a6a>] trace_selftest_startup_function+0xda/0x2b0
[  593.149895]  [<ffffffff81146c4c>] register_tracer+0x32c/0x430
[  593.149895]  [<ffffffff81c3aee4>] ? init_trace_printk_function_export+0x48/0x48
[  593.149895]  [<ffffffff81c3aef4>] init_function_trace+0x10/0x12
[  593.149895]  [<ffffffff8100223a>] do_one_initcall+0x1aa/0x270
[  593.149895]  [<ffffffff815313bc>] kernel_init+0x11c/0x370
[  593.149895]  [<ffffffff81c17878>] ? do_early_param+0xc6/0xc6
[  593.149895]  [<ffffffff810ca474>] ? schedule_tail+0x34/0x110
[  593.149895]  [<ffffffff815312a0>] ? rest_init+0x170/0x170
[  593.149895]  [<ffffffff815739ac>] ret_from_fork+0x7c/0xb0
[  593.149895]  [<ffffffff815312a0>] ? rest_init+0x170/0x170

And it's bisected down to an unbelievable simple commit..

commit 17bb615ad4f8d2d2c0f02794d27d7f83e0009ef4
Author: Steven Rostedt <srostedt@redhat.com>
Date:   Mon May 23 15:27:46 2011 -0400

    tracing: Have event with function tracer check error return

Thanks,
Fengguang