Paul,

I got the below warning in stable kernel 3.6.3. linux-next does
not have this issue. Bisect shows that the first bad commit is

commit b1420f1c8bfc30ecf6380a31d0f686884834b599
Author: Paul E. McKenney <paul.mckenney@linaro.org>
Date:   Thu Mar 1 13:18:08 2012 -0800

    rcu: Make rcu_barrier() less disruptive


[   92.252733] do_IRQ: 1.59 No irq handler for vector (irq -1)
[   92.253257] ------------[ cut here ]------------
[   92.253675] WARNING: at /c/kernel-tests/src/stable/kernel/rcutree.c:1562 rcu_do_batch+0x17e/0x63b()
[   92.254474] Hardware name: Bochs
[   92.254766] Modules linked in:
[   92.256689] Pid: 9, comm: migration/1 Not tainted 3.6.3 #1306
[   92.256689] Call Trace:
[   92.256689]  <IRQ>  [<ffffffff81033dbd>] warn_slowpath_common+0x83/0x9c
[   92.256689]  [<ffffffff81033df0>] warn_slowpath_null+0x1a/0x1c
[   92.256689]  [<ffffffff810a70fd>] rcu_do_batch+0x17e/0x63b
[   92.256689]  [<ffffffff810a6705>] ? rcu_report_qs_rnp+0x28b/0x2d5
[   92.256689]  [<ffffffff810a769d>] ? rcu_process_callbacks+0xe3/0x236
[   92.256689]  [<ffffffff810a772c>] rcu_process_callbacks+0x172/0x236
[   92.256689]  [<ffffffff8103b6cc>] __do_softirq+0xf6/0x231
[   92.256689]  [<ffffffff8107fe2c>] ? tick_program_event+0x24/0x26
[   92.256689]  [<ffffffff817d23bc>] call_softirq+0x1c/0x30
[   92.256689]  [<ffffffff81003f7c>] do_softirq+0x4a/0xa6
[   92.256689]  [<ffffffff8103ba98>] irq_exit+0x51/0xbc
[   92.256689]  [<ffffffff817d2a2f>] smp_apic_timer_interrupt+0x8b/0x99
[   92.256689]  [<ffffffff817d1c2f>] apic_timer_interrupt+0x6f/0x80
[   92.256689]  <EOI>  [<ffffffff81067440>] ? local_clock+0x1d/0x5a
[   92.256689]  [<ffffffff8109ea37>] ? stop_machine_cpu_stop+0x104/0x119
[   92.256689]  [<ffffffff8109e6d5>] cpu_stopper_thread+0xdd/0x17d
[   92.256689]  [<ffffffff8109e933>] ? queue_stop_cpus_work+0x130/0x130
[   92.256689]  [<ffffffff817ca044>] ? _raw_spin_unlock_irqrestore+0x47/0x65
[   92.256689]  [<ffffffff81086613>] ? trace_hardirqs_on_caller+0x125/0x181
[   92.256689]  [<ffffffff8108667c>] ? trace_hardirqs_on+0xd/0xf
[   92.256689]  [<ffffffff8109e5f8>] ? cpu_stop_signal_done+0x2c/0x2c
[   92.256689]  [<ffffffff81055e74>] kthread+0x9a/0xa2
[   92.256689]  [<ffffffff817d22c4>] kernel_thread_helper+0x4/0x10
[   92.256689]  [<ffffffff817ca4b0>] ? retint_restore_args+0x13/0x13
[   92.256689]  [<ffffffff81055dda>] ? __init_kthread_worker+0x5a/0x5a
[   92.317029]  [<ffffffff817d22c0>] ? gs_change+0x13/0x13

Thanks,
Fengguang