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SubjectLockdep splat in 3.0-rc6
I've been seeing this for a while in the 3.0 series..and it's still
in -rc6. This kernel is larded up with debug options, and is
running some nfs/rpc patches not in the standard tree. It is
heavily loaded doing nfs mounts, traffic, unmounts, etc. As
far as I can tell, this has nothing in particular to do with
NFS.


======================================================
[ INFO: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected ]
3.0.0-rc6+ #13
------------------------------------------------------
ps/25695 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
(&lock->wait_lock){+.+...}, at: [<ffffffff8147dfa0>] rt_mutex_slowunlock+0x1d/0xdd

and this task is already holding:
(&(&sighand->siglock)->rlock){-.....}, at: [<ffffffff8105a4e3>] __lock_task_sighand+0x6e/0x9c
which would create a new lock dependency:
(&(&sighand->siglock)->rlock){-.....} -> (&lock->wait_lock){+.+...}

but this new dependency connects a HARDIRQ-irq-safe lock:
(&(&sighand->siglock)->rlock){-.....}
... which became HARDIRQ-irq-safe at:
[<ffffffff8107a4b0>] __lock_acquire+0x2b4/0xdd5
[<ffffffff8107b4d5>] lock_acquire+0xf4/0x14b
[<ffffffff8147e565>] _raw_spin_lock_irqsave+0x4e/0x60
[<ffffffff8105a4e3>] __lock_task_sighand+0x6e/0x9c
[<ffffffff8105b27f>] do_send_sig_info+0x27/0x70
[<ffffffff8105b55b>] group_send_sig_info+0x4c/0x57
[<ffffffff8105b5a5>] kill_pid_info+0x3f/0x5a
[<ffffffff8104eb39>] it_real_fn+0x85/0xb4
[<ffffffff8106a598>] __run_hrtimer+0xbe/0x1be
[<ffffffff8106a9bc>] hrtimer_interrupt+0xe5/0x1c0
[<ffffffff8102328c>] smp_apic_timer_interrupt+0x80/0x93
[<ffffffff81485793>] apic_timer_interrupt+0x13/0x20
[<ffffffff81009e87>] cpu_idle+0x5e/0xb5
[<ffffffff81477e69>] start_secondary+0x1a3/0x1a8

to a HARDIRQ-irq-unsafe lock:
(&lock->wait_lock){+.+...}
... which became HARDIRQ-irq-unsafe at:
... [<ffffffff8107a524>] __lock_acquire+0x328/0xdd5
[<ffffffff8107b4d5>] lock_acquire+0xf4/0x14b
[<ffffffff8147e451>] _raw_spin_lock+0x36/0x45
[<ffffffff8147e0af>] rt_mutex_slowlock+0x2b/0x132
[<ffffffff8147e254>] rt_mutex_lock+0x46/0x4a
[<ffffffff810a6bd1>] rcu_boost_kthread+0x125/0x169
[<ffffffff81066f9c>] kthread+0x7d/0x85
[<ffffffff81485ee4>] kernel_thread_helper+0x4/0x10

other info that might help us debug this:

Possible interrupt unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&lock->wait_lock);
local_irq_disable();
lock(&(&sighand->siglock)->rlock);
lock(&lock->wait_lock);
<Interrupt>
lock(&(&sighand->siglock)->rlock);

*** DEADLOCK ***

2 locks held by ps/25695:
#0: (&p->lock){+.+.+.}, at: [<ffffffff81134abc>] seq_read+0x38/0x368
#1: (&(&sighand->siglock)->rlock){-.....}, at: [<ffffffff8105a4e3>] __lock_task_sighand+0x6e/0x9c

the dependencies between HARDIRQ-irq-safe lock and the holding lock:
-> (&(&sighand->siglock)->rlock){-.....} ops: 30710408 {
IN-HARDIRQ-W at:
[<ffffffff8107a4b0>] __lock_acquire+0x2b4/0xdd5
[<ffffffff8107b4d5>] lock_acquire+0xf4/0x14b
[<ffffffff8147e565>] _raw_spin_lock_irqsave+0x4e/0x60
[<ffffffff8105a4e3>] __lock_task_sighand+0x6e/0x9c
[<ffffffff8105b27f>] do_send_sig_info+0x27/0x70
[<ffffffff8105b55b>] group_send_sig_info+0x4c/0x57
[<ffffffff8105b5a5>] kill_pid_info+0x3f/0x5a
[<ffffffff8104eb39>] it_real_fn+0x85/0xb4
[<ffffffff8106a598>] __run_hrtimer+0xbe/0x1be
[<ffffffff8106a9bc>] hrtimer_interrupt+0xe5/0x1c0
[<ffffffff8102328c>] smp_apic_timer_interrupt+0x80/0x93
[<ffffffff81485793>] apic_timer_interrupt+0x13/0x20
[<ffffffff81009e87>] cpu_idle+0x5e/0xb5
[<ffffffff81477e69>] start_secondary+0x1a3/0x1a8
INITIAL USE at:
[<ffffffff8107a59b>] __lock_acquire+0x39f/0xdd5
[<ffffffff8107b4d5>] lock_acquire+0xf4/0x14b
[<ffffffff8147e565>] _raw_spin_lock_irqsave+0x4e/0x60
[<ffffffff8105a64b>] flush_signals+0x1d/0x43
[<ffffffff8105a699>] ignore_signals+0x28/0x2a
[<ffffffff81066fe2>] kthreadd+0x3e/0x13d
[<ffffffff81485ee4>] kernel_thread_helper+0x4/0x10
}
... key at: [<ffffffff81c45510>] __key.56506+0x0/0x8
... acquired at:
[<ffffffff81079ede>] check_irq_usage+0x5d/0xbe
[<ffffffff8107ad05>] __lock_acquire+0xb09/0xdd5
[<ffffffff8107b4d5>] lock_acquire+0xf4/0x14b
[<ffffffff8147e451>] _raw_spin_lock+0x36/0x45
[<ffffffff8147dfa0>] rt_mutex_slowunlock+0x1d/0xdd
[<ffffffff8147e082>] rt_mutex_unlock+0x22/0x24
[<ffffffff810a8009>] __rcu_read_unlock+0x1c0/0x24e
[<ffffffff8105a413>] rcu_read_unlock+0x21/0x23
[<ffffffff8105a502>] __lock_task_sighand+0x8d/0x9c
[<ffffffff8116cab6>] do_task_stat+0x11d/0x84a
[<ffffffff8116d1f2>] proc_tgid_stat+0xf/0x11
[<ffffffff81169f3b>] proc_single_show+0x54/0x71
[<ffffffff81134c05>] seq_read+0x181/0x368
[<ffffffff81119e9a>] vfs_read+0xa6/0x102
[<ffffffff81119faf>] sys_read+0x45/0x6c
[<ffffffff81484d52>] system_call_fastpath+0x16/0x1b


the dependencies between the lock to be acquired and HARDIRQ-irq-unsafe lock:
-> (&lock->wait_lock){+.+...} ops: 725 {
HARDIRQ-ON-W at:
[<ffffffff8107a524>] __lock_acquire+0x328/0xdd5
[<ffffffff8107b4d5>] lock_acquire+0xf4/0x14b
[<ffffffff8147e451>] _raw_spin_lock+0x36/0x45
[<ffffffff8147e0af>] rt_mutex_slowlock+0x2b/0x132
[<ffffffff8147e254>] rt_mutex_lock+0x46/0x4a
[<ffffffff810a6bd1>] rcu_boost_kthread+0x125/0x169
[<ffffffff81066f9c>] kthread+0x7d/0x85
[<ffffffff81485ee4>] kernel_thread_helper+0x4/0x10
SOFTIRQ-ON-W at:
[<ffffffff8107a545>] __lock_acquire+0x349/0xdd5
[<ffffffff8107b4d5>] lock_acquire+0xf4/0x14b
[<ffffffff8147e451>] _raw_spin_lock+0x36/0x45
[<ffffffff8147e0af>] rt_mutex_slowlock+0x2b/0x132
[<ffffffff8147e254>] rt_mutex_lock+0x46/0x4a
[<ffffffff810a6bd1>] rcu_boost_kthread+0x125/0x169
[<ffffffff81066f9c>] kthread+0x7d/0x85
[<ffffffff81485ee4>] kernel_thread_helper+0x4/0x10
INITIAL USE at:
[<ffffffff8107a59b>] __lock_acquire+0x39f/0xdd5
[<ffffffff8107b4d5>] lock_acquire+0xf4/0x14b
[<ffffffff8147e451>] _raw_spin_lock+0x36/0x45
[<ffffffff8147e0af>] rt_mutex_slowlock+0x2b/0x132
[<ffffffff8147e254>] rt_mutex_lock+0x46/0x4a
[<ffffffff810a6bd1>] rcu_boost_kthread+0x125/0x169
[<ffffffff81066f9c>] kthread+0x7d/0x85
[<ffffffff81485ee4>] kernel_thread_helper+0x4/0x10
}
... key at: [<ffffffff824759b0>] __key.22188+0x0/0x8
... acquired at:
[<ffffffff81079ede>] check_irq_usage+0x5d/0xbe
[<ffffffff8107ad05>] __lock_acquire+0xb09/0xdd5
[<ffffffff8107b4d5>] lock_acquire+0xf4/0x14b
[<ffffffff8147e451>] _raw_spin_lock+0x36/0x45
[<ffffffff8147dfa0>] rt_mutex_slowunlock+0x1d/0xdd
[<ffffffff8147e082>] rt_mutex_unlock+0x22/0x24
[<ffffffff810a8009>] __rcu_read_unlock+0x1c0/0x24e
[<ffffffff8105a413>] rcu_read_unlock+0x21/0x23
[<ffffffff8105a502>] __lock_task_sighand+0x8d/0x9c
[<ffffffff8116cab6>] do_task_stat+0x11d/0x84a
[<ffffffff8116d1f2>] proc_tgid_stat+0xf/0x11
[<ffffffff81169f3b>] proc_single_show+0x54/0x71
[<ffffffff81134c05>] seq_read+0x181/0x368
[<ffffffff81119e9a>] vfs_read+0xa6/0x102
[<ffffffff81119faf>] sys_read+0x45/0x6c
[<ffffffff81484d52>] system_call_fastpath+0x16/0x1b


stack backtrace:
Pid: 25695, comm: ps Not tainted 3.0.0-rc6+ #13
Call Trace:
[<ffffffff81079e6d>] check_usage+0x364/0x378
[<ffffffff81079ede>] check_irq_usage+0x5d/0xbe
[<ffffffff8107ad05>] __lock_acquire+0xb09/0xdd5
[<ffffffff810a7155>] ? rcu_start_gp+0x2e7/0x310
[<ffffffff8147dfa0>] ? rt_mutex_slowunlock+0x1d/0xdd
[<ffffffff8107b4d5>] lock_acquire+0xf4/0x14b
[<ffffffff8147dfa0>] ? rt_mutex_slowunlock+0x1d/0xdd
[<ffffffff8147e451>] _raw_spin_lock+0x36/0x45
[<ffffffff8147dfa0>] ? rt_mutex_slowunlock+0x1d/0xdd
[<ffffffff8147dfa0>] rt_mutex_slowunlock+0x1d/0xdd
[<ffffffff8147e082>] rt_mutex_unlock+0x22/0x24
[<ffffffff810a8009>] __rcu_read_unlock+0x1c0/0x24e
[<ffffffff8105a413>] rcu_read_unlock+0x21/0x23
[<ffffffff8105a502>] __lock_task_sighand+0x8d/0x9c
[<ffffffff8116cab6>] do_task_stat+0x11d/0x84a
[<ffffffff81077ef3>] ? register_lock_class+0x1e/0x336
[<ffffffff81078f79>] ? mark_lock+0x2d/0x22d
[<ffffffff81078f79>] ? mark_lock+0x2d/0x22d
[<ffffffff8107a59b>] ? __lock_acquire+0x39f/0xdd5
[<ffffffff81105602>] ? add_partial+0x1b/0x53
[<ffffffff81063d3f>] ? cpumask_weight+0xe/0xe
[<ffffffff8116d1f2>] proc_tgid_stat+0xf/0x11
[<ffffffff81169f3b>] proc_single_show+0x54/0x71
[<ffffffff81134c05>] seq_read+0x181/0x368
[<ffffffff81119e9a>] vfs_read+0xa6/0x102
[<ffffffff8111a4e9>] ? fget_light+0x35/0xac
[<ffffffff81119faf>] sys_read+0x45/0x6c
[<ffffffff81484d52>] system_call_fastpath+0x16/0x1b


--
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc http://www.candelatech.com



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