Hi Paul,

I've just bisected down one RCU stall problem:

[   12.035785] pktgen: Packet Generator for packet performance testing. Version: 2.74
[   12.435439] atkbd: probe of serio0 rejects match -19
[  111.700160] INFO: rcu_preempt detected stalls on CPUs/tasks: { 1} (detected by 0, t=10002 jiffies)
[  111.700171] Pid: 0, comm: swapper/0 Not tainted 3.6.0-rc5-00004-gda10491 #1
[  111.700178] Call Trace:
[  111.700475]  [<c10c3c84>] rcu_check_callbacks+0x544/0x570
[  111.700538]  [<c1075e86>] update_process_times+0x36/0x70
[  111.700547]  [<c10a6267>] tick_sched_timer+0x57/0xc0
[  111.700552]  [<c108758a>] __run_hrtimer.isra.31+0x4a/0xc0
[  111.700557]  [<c10a6210>] ? tick_nohz_handler+0xf0/0xf0
[  111.700559]  [<c1088155>] hrtimer_interrupt+0xf5/0x290
[  111.700562]  [<c1091cb8>] ? sched_clock_idle_wakeup_event+0x18/0x20
[  111.700565]  [<c10a6399>] ? tick_nohz_stop_idle+0x39/0x40
[  111.700572]  [<c104f56f>] smp_apic_timer_interrupt+0x4f/0x80
[  111.700587]  [<c1753636>] apic_timer_interrupt+0x2a/0x30
[  111.700593]  [<c10565b5>] ? native_safe_halt+0x5/0x10
[  111.700599]  [<c1039f89>] default_idle+0x29/0x50
[  111.700601]  [<c103a958>] cpu_idle+0x68/0xb0
[  111.700609]  [<c16f2ff7>] rest_init+0x67/0x70
[  111.700627]  [<c1af7929>] start_kernel+0x2ea/0x2f0
[  111.700629]  [<c1af7474>] ? repair_env_string+0x51/0x51
[  111.700631]  [<c1af72a2>] i386_start_kernel+0x78/0x7d
[  127.040302] bus: 'serio': driver_probe_device: matched device serio0 with driver atkbd
[  127.041308] CPA self-test:

to this commit:

commit 06ae115a1d551cd952d80df06eaf8b5153351875
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date:   Sun Aug 14 15:56:54 2011 -0700

    rcu: Avoid having just-onlined CPU resched itself when RCU is idle

Thanks,
Fengguang