[BUG] 2.6.28-git LOCKDEP: Possible recursive rq->lock

[Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>]

Hi Ingo,

Kernbench runs on latest Linux git tree stalled with the following
lockdep warning.

Lockdep warning and lockup on Jan 3 Linus git tree
commit 7d3b56ba37a95f1f370f50258ed3954c304c524b

kernbench run with two threads stalled.  sched_mc was zero.
x86_64 system with 8 logical CPUs in dual socket quad core
configuration.

I will post more information as I debug this warning/bug.  

--Vaidy


 kernel: =============================================
 kernel: [ INFO: possible recursive locking detected ]
 kernel: 2.6.28-autotest-sv #1
 kernel: ---------------------------------------------
 kernel: autotest/6230 is trying to acquire lock:
 kernel:  (&rq->lock){++..}, at: [<ffffffff80229240>] task_rq_lock+0x44/0x7e
 kernel:
 kernel: but task is already holding lock:
 kernel:  (&rq->lock){++..}, at: [<ffffffff805d0fd4>] schedule+0x144/0x9d6
 kernel:
 kernel: other info that might help us debug this:
 kernel: 1 lock held by autotest/6230:
 kernel:  #0:  (&rq->lock){++..}, at: [<ffffffff805d0fd4>] schedule+0x144/0x9d6
 kernel:
 kernel: stack backtrace:
 kernel: Pid: 6230, comm: autotest Not tainted 2.6.28-autotest-sv #1
 kernel: Call Trace:
 kernel:  [<ffffffff802560d8>] __lock_acquire+0xe2a/0x15ed
 kernel:  [<ffffffff80256920>] lock_acquire+0x85/0xa9
 kernel:  [<ffffffff80229240>] task_rq_lock+0x44/0x7e
 kernel:  [<ffffffff805d3f4c>] _spin_lock+0x2d/0x5f
 kernel:  [<ffffffff80229240>] task_rq_lock+0x44/0x7e
 kernel:  [<ffffffff80229240>] task_rq_lock+0x44/0x7e
 kernel:  [<ffffffff8022de2e>] try_to_wake_up+0x83/0x26f
 kernel:  [<ffffffff805d0fd4>] schedule+0x144/0x9d6
 kernel:  [<ffffffff805d13e8>] schedule+0x558/0x9d6
 kernel:  [<ffffffff802549c8>] trace_hardirqs_on_caller+0x120/0x14a
 kernel:  [<ffffffff8024a241>] hrtimer_start_range_ns+0x143/0x156
 kernel:  [<ffffffff805d2b82>] schedule_hrtimeout_range+0xcc/0xff
 kernel:  [<ffffffff80249ba0>] hrtimer_wakeup+0x0/0x22
 kernel:  [<ffffffff805d2b64>] schedule_hrtimeout_range+0xae/0xff
 kernel:  [<ffffffff802aa6e8>] do_select+0x502/0x55d
 kernel:  [<ffffffff802aa1e6>] do_select+0x0/0x55d
 kernel:  [<ffffffff802aac5f>] __pollwait+0x0/0xe5
 kernel:  [<ffffffff8022e01a>] default_wake_function+0x0/0x9
 kernel:  [<ffffffff8022e01a>] default_wake_function+0x0/0x9
 kernel:  [<ffffffff80256882>] __lock_acquire+0x15d4/0x15ed
 last message repeated 2 times
 kernel:  [<ffffffff80252913>] lock_release_holdtime+0x1b/0x16c
 kernel:  [<ffffffff80252913>] lock_release_holdtime+0x1b/0x16c
 kernel:  [<ffffffff802aa774>] core_sys_select+0x31/0x2b0
 kernel:  [<ffffffff802aa92f>] core_sys_select+0x1ec/0x2b0
 kernel:  [<ffffffff802aa774>] core_sys_select+0x31/0x2b0
 kernel:  [<ffffffff8024785b>] remove_wait_queue+0x12/0x41
 kernel:  [<ffffffff80252913>] lock_release_holdtime+0x1b/0x16c
 kernel:  [<ffffffff805d3dc9>] _spin_unlock_irqrestore+0x3e/0x44
 kernel:  [<ffffffff802549c8>] trace_hardirqs_on_caller+0x120/0x14a
 kernel:  [<ffffffff80237c6e>] do_wait+0x2a4/0x395
 kernel:  [<ffffffff8024cc09>] getnstimeofday+0x38/0x92
 kernel:  [<ffffffff802aac36>] sys_select+0x92/0xbb
 kernel:  [<ffffffff8020bedb>] system_call_fastpath+0x16/0x1b