tty/perf lockdep trace.

[Dave Jones]

 ======================================================
 [ INFO: possible circular locking dependency detected ]
 3.12.0-rc3+ #92 Not tainted
 -------------------------------------------------------
 trinity-child2/15191 is trying to acquire lock:
  (&rdp->nocb_wq){......}, at: [<ffffffff8108ff43>] __wake_up+0x23/0x50
 
but task is already holding lock:
  (&ctx->lock){-.-...}, at: [<ffffffff81154c19>] perf_event_exit_task+0x109/0x230

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&ctx->lock){-.-...}:
        [<ffffffff810cc243>] lock_acquire+0x93/0x200
        [<ffffffff81733f90>] _raw_spin_lock+0x40/0x80
        [<ffffffff811500ff>] __perf_event_task_sched_out+0x2df/0x5e0
        [<ffffffff81091b83>] perf_event_task_sched_out+0x93/0xa0
        [<ffffffff81732052>] __schedule+0x1d2/0xa20
        [<ffffffff81732f30>] preempt_schedule_irq+0x50/0xb0
        [<ffffffff817352b6>] retint_kernel+0x26/0x30
        [<ffffffff813eed04>] tty_flip_buffer_push+0x34/0x50
        [<ffffffff813f0504>] pty_write+0x54/0x60
        [<ffffffff813e900d>] n_tty_write+0x32d/0x4e0
        [<ffffffff813e5838>] tty_write+0x158/0x2d0
        [<ffffffff811c4850>] vfs_write+0xc0/0x1f0
        [<ffffffff811c52cc>] SyS_write+0x4c/0xa0
        [<ffffffff8173d4e4>] tracesys+0xdd/0xe2
 
-> #2 (&rq->lock){-.-.-.}:
        [<ffffffff810cc243>] lock_acquire+0x93/0x200
        [<ffffffff81733f90>] _raw_spin_lock+0x40/0x80
        [<ffffffff810980b2>] wake_up_new_task+0xc2/0x2e0
        [<ffffffff81054336>] do_fork+0x126/0x460
        [<ffffffff81054696>] kernel_thread+0x26/0x30
        [<ffffffff8171ff93>] rest_init+0x23/0x140
        [<ffffffff81ee1e4b>] start_kernel+0x3f6/0x403
        [<ffffffff81ee1571>] x86_64_start_reservations+0x2a/0x2c
        [<ffffffff81ee1664>] x86_64_start_kernel+0xf1/0xf4
 
-> #1 (&p->pi_lock){-.-.-.}:
        [<ffffffff810cc243>] lock_acquire+0x93/0x200
        [<ffffffff8173419b>] _raw_spin_lock_irqsave+0x4b/0x90
        [<ffffffff810979d1>] try_to_wake_up+0x31/0x350
        [<ffffffff81097d62>] default_wake_function+0x12/0x20
        [<ffffffff81084af8>] autoremove_wake_function+0x18/0x40
        [<ffffffff8108ea38>] __wake_up_common+0x58/0x90
        [<ffffffff8108ff59>] __wake_up+0x39/0x50
        [<ffffffff8110d4f8>] __call_rcu_nocb_enqueue+0xa8/0xc0
        [<ffffffff81111450>] __call_rcu+0x140/0x820
        [<ffffffff81111b8d>] call_rcu+0x1d/0x20
        [<ffffffff81093697>] cpu_attach_domain+0x287/0x360
        [<ffffffff81099d7e>] build_sched_domains+0xe5e/0x10a0
        [<ffffffff81efa7fc>] sched_init_smp+0x3b7/0x47a
        [<ffffffff81ee1f4e>] kernel_init_freeable+0xf6/0x202
        [<ffffffff817200be>] kernel_init+0xe/0x190
        [<ffffffff8173d22c>] ret_from_fork+0x7c/0xb0
 
-> #0 (&rdp->nocb_wq){......}:
        [<ffffffff810cb7ca>] __lock_acquire+0x191a/0x1be0
        [<ffffffff810cc243>] lock_acquire+0x93/0x200
        [<ffffffff8173419b>] _raw_spin_lock_irqsave+0x4b/0x90
        [<ffffffff8108ff43>] __wake_up+0x23/0x50
        [<ffffffff8110d4f8>] __call_rcu_nocb_enqueue+0xa8/0xc0
        [<ffffffff81111450>] __call_rcu+0x140/0x820
        [<ffffffff81111bb0>] kfree_call_rcu+0x20/0x30
        [<ffffffff81149abf>] put_ctx+0x4f/0x70
        [<ffffffff81154c3e>] perf_event_exit_task+0x12e/0x230
        [<ffffffff81056b8d>] do_exit+0x30d/0xcc0
        [<ffffffff8105893c>] do_group_exit+0x4c/0xc0
        [<ffffffff810589c4>] SyS_exit_group+0x14/0x20
        [<ffffffff8173d4e4>] tracesys+0xdd/0xe2
 
other info that might help us debug this:

Chain exists of:
  &rdp->nocb_wq --> &rq->lock --> &ctx->lock

  Possible unsafe locking scenario:

        CPU0                    CPU1
        ----                    ----
   lock(&ctx->lock);
                                lock(&rq->lock);
                                lock(&ctx->lock);
   lock(&rdp->nocb_wq);
 
 *** DEADLOCK ***

1 lock held by trinity-child2/15191:
 #0:  (&ctx->lock){-.-...}, at: [<ffffffff81154c19>] perf_event_exit_task+0x109/0x230

stack backtrace:
CPU: 2 PID: 15191 Comm: trinity-child2 Not tainted 3.12.0-rc3+ #92 
 ffffffff82565b70 ffff880070c2dbf8 ffffffff8172a363 ffffffff824edf40
 ffff880070c2dc38 ffffffff81726741 ffff880070c2dc90 ffff88022383b1c0
 ffff88022383aac0 0000000000000000 ffff88022383b188 ffff88022383b1c0
Call Trace:
 [<ffffffff8172a363>] dump_stack+0x4e/0x82
 [<ffffffff81726741>] print_circular_bug+0x200/0x20f
 [<ffffffff810cb7ca>] __lock_acquire+0x191a/0x1be0
 [<ffffffff810c6439>] ? get_lock_stats+0x19/0x60
 [<ffffffff8100b2f4>] ? native_sched_clock+0x24/0x80
 [<ffffffff810cc243>] lock_acquire+0x93/0x200
 [<ffffffff8108ff43>] ? __wake_up+0x23/0x50
 [<ffffffff8173419b>] _raw_spin_lock_irqsave+0x4b/0x90
 [<ffffffff8108ff43>] ? __wake_up+0x23/0x50
 [<ffffffff8108ff43>] __wake_up+0x23/0x50
 [<ffffffff8110d4f8>] __call_rcu_nocb_enqueue+0xa8/0xc0
 [<ffffffff81111450>] __call_rcu+0x140/0x820
 [<ffffffff8109bc8f>] ? local_clock+0x3f/0x50
 [<ffffffff81111bb0>] kfree_call_rcu+0x20/0x30
 [<ffffffff81149abf>] put_ctx+0x4f/0x70
 [<ffffffff81154c3e>] perf_event_exit_task+0x12e/0x230
 [<ffffffff81056b8d>] do_exit+0x30d/0xcc0
 [<ffffffff810c9af5>] ? trace_hardirqs_on_caller+0x115/0x1e0
 [<ffffffff810c9bcd>] ? trace_hardirqs_on+0xd/0x10
 [<ffffffff8105893c>] do_group_exit+0x4c/0xc0
 [<ffffffff810589c4>] SyS_exit_group+0x14/0x20
 [<ffffffff8173d4e4>] tracesys+0xdd/0xe2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/