Hi Steven, Paul,

Here is yet another warning, triggered by:

                if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
                        printk("possible reason: unannotated irqs-on.\n");
                }

For the same attached config, there are two different stack traces
show up alternatively in the test boots,

=== 1 ===

[    4.587462] Testing tracer irqsoff: PASSED
[    5.361624] Testing tracer branch: [    5.487614] ------------[ cut here ]------------
[    5.488906] WARNING: at /c/wfg/linux/kernel/lockdep.c:3493 check_flags+0xab/0x1a0()
[    5.490874] Hardware name: Bochs
[    5.491810] Pid: 29, comm: rcu_torture_rea Not tainted 3.5.0-00551-g08843b7-dirty #7
[    5.493793] Call Trace:

[    5.494692]  [<c104f72d>] warn_slowpath_common+0x9d/0xd0
[    5.496369]  [<c10c1cbb>] ? check_flags+0xab/0x1a0
[    5.497419]  [<c10c1cbb>] ? check_flags+0xab/0x1a0
[    5.497419]  [<c103c1a0>] ? native_restore_fl+0x10/0x10
[    5.497419]  [<c104f822>] warn_slowpath_null+0x22/0x30
[    5.497419]  [<c10c1cbb>] check_flags+0xab/0x1a0
[    5.497419]  [<c10c4179>] lock_acquire+0x59/0x130
[    5.497419]  [<c10eb0e8>] rcu_torture_read_lock+0x38/0x40
[    5.497419]  [<c10eb0b0>] ? rcu_random+0x80/0x80
[    5.497419]  [<c10edccb>] rcu_torture_reader+0xab/0x330
[    5.497419]  [<c10edf50>] ? rcu_torture_reader+0x330/0x330
[    5.497419]  [<c10edc20>] ? rcutorture_trace_dump+0x80/0x80
[    5.497419]  [<c108781b>] kthread+0x8b/0xa0
[    5.497419]  [<c1450000>] ? slab_out_of_memory.constprop.55+0xe2/0xf0
[    5.497419]  [<c1087790>] ? insert_kthread_work+0xf0/0xf0
[    5.497419]  [<c145b5fa>] kernel_thread_helper+0x6/0x10

=== 2 ===

[   10.338285] Testing tracer irqsoff: PASSED
[   10.788310] Testing tracer branch: [   10.882125] ------------[ cut here ]------------
[   10.884047] WARNING: at /c/kernel-tests/src/tip/kernel/lockdep.c:3493 check_flags+0xab/0x1a0()
[   10.886964] Hardware name: Bochs
[   10.887916] Pid: 0, comm: swapper/1 Not tainted 3.5.0-00551-g08843b7 #1
[   10.889646] Call Trace:

[   10.890412]  [<c104f72d>] warn_slowpath_common+0x9d/0xd0
[   10.892017]  [<c10c1cbb>] ? check_flags+0xab/0x1a0
[   10.892017]  [<c10c1cbb>] ? check_flags+0xab/0x1a0
[   10.892017]  [<c103c1a0>] ? native_restore_fl+0x10/0x10
[   10.892017]  [<c104f822>] warn_slowpath_null+0x22/0x30
[   10.892017]  [<c10c1cbb>] check_flags+0xab/0x1a0
[   10.892017]  [<c10c4179>] lock_acquire+0x59/0x130
[   10.892017]  [<c10674b8>] run_timer_softirq+0x238/0x4e0
[   10.892017]  [<c106745e>] ? run_timer_softirq+0x1de/0x4e0
[   10.892017]  [<c1067760>] ? run_timer_softirq+0x4e0/0x4e0
[   10.892017]  [<c105cf01>] __do_softirq+0x151/0x320
[   10.892017]  [<c105cdb0>] ? local_bh_enable_ip+0x270/0x270
[   10.892017]  <IRQ>  [<c105d495>] ? irq_exit+0x95/0xa0
[   10.892017]  [<c1030fbb>] ? smp_apic_timer_interrupt+0x7b/0xc0
[   10.892017]  [<c145ac9f>] ? apic_timer_interrupt+0x2f/0x34
[   10.892017]  [<c103c1c5>] ? native_safe_halt+0x5/0x10
[   10.892017]  [<c1010404>] ? default_idle+0x204/0x210
[   10.892017]  [<c10114da>] ? cpu_idle+0x15a/0x1a0
[   10.892017]  [<c1445e7f>] ? start_secondary+0x3f4/0x523

Thanks,
Fengguang