Re: lockdep question (was Re: IPoIB caused a kernel: BUG: softlockup detected on CPU#0!)

[Peter Zijlstra]

On Sun, 2007-03-11 at 15:50 +0200, Michael S. Tsirkin wrote:
> > Quoting Roland Dreier <roland.list@xxxxxxxxx>:
> > Subject: Re: IPoIB caused a kernel: BUG: soft lockup detected on CPU#0!
> > 
> > >Feb 27 17:47:52 sw169 kernel:  [<ffffffff8053aaf1>] _spin_lock_irqsave+0x15/0x24
> > >Feb 27 17:47:52 sw169 kernel:  [<ffffffff88067a23>] :ib_ipoib:ipoib_neigh_destructor+0xc2/0x139
> > 
> > It looks like this is deadlocking trying to take priv->lock in ipoib_neigh_destructor().
> > One idea I just had would be to build a kernel with CONFIG_PROVE_LOCKING 
> > turned on, and then rerun this test.  There's a good chance that this would
> > diagnose the deadlock.  (I don't have good access to my test machines right now, or
> > else I would do it myself)
> 
> OK, I did that. But I get
> 	[13440.761857] INFO: trying to register non-static key.
> 	[13440.766903] the code is fine but needs lockdep annotation.
> 	[13440.772455] turning off the locking correctness validator.
> and I am not sure what triggers this, or how to fix it to have the
> validator actually do its job.

It usually indicates a spinlock is not properly initialized. Like
__SPIN_LOCK_UNLOCKED() used in a non-static context, use
spin_lock_init() in these cases.

However looking at the code, ipoib_neight_destructor only uses
&priv->lock, and that seems to get properly initialized in ipoib_setup()
using spin_lock_init().

So either there are other sites that instanciate those objects and
forget about the lock init, or the object is corrupted (use after free?)

> Ingo, what key does the message refer to?
> 
> The stack dump seems to point to drivers/infiniband/ulp/ipoib/ipoib_main.c line
> 829.
> 
> Full message below:
> 	
> [13440.761857] INFO: trying to register non-static key.
> [13440.766903] the code is fine but needs lockdep annotation.
> [13440.772455] turning off the locking correctness validator.
> [13440.778008]  [<c023c082>] __lock_acquire+0xae4/0xbb9
> [13440.783078]  [<c023c43d>] lock_acquire+0x56/0x71
> [13440.787784]  [<f899bff2>] ipoib_neigh_destructor+0xd0/0x132 [ib_ipoib]
> [13440.794412]  [<c051ad41>] _spin_lock_irqsave+0x32/0x41
> [13440.799649]  [<f899bff2>] ipoib_neigh_destructor+0xd0/0x132 [ib_ipoib]
> [13440.806275]  [<f899bff2>] ipoib_neigh_destructor+0xd0/0x132 [ib_ipoib]
> [13440.812897]  [<c04a1c1b>] dst_run_gc+0xc/0x118
> [13440.817439]  [<c022af6e>] run_timer_softirq+0x37/0x16b
> [13440.822673]  [<c04a1c0f>] dst_run_gc+0x0/0x118
> [13440.827221]  [<c04a3eab>] neigh_destroy+0xbe/0x104
> [13440.832114]  [<c04a1bb1>] dst_destroy+0x4d/0xab
> [13440.836751]  [<c04a1c64>] dst_run_gc+0x55/0x118
> [13440.841384]  [<c022b03f>] run_timer_softirq+0x108/0x16b
> [13440.846711]  [<c0227634>] __do_softirq+0x5a/0xd5
> [13440.851427]  [<c023b435>] trace_hardirqs_on+0x106/0x141
> [13440.856754]  [<c0227643>] __do_softirq+0x69/0xd5
> [13440.861470]  [<c02276e6>] do_softirq+0x37/0x4d
> [13440.866016]  [<c02167b0>] smp_apic_timer_interrupt+0x6b/0x77
> [13440.871774]  [<c02029ef>] default_idle+0x3b/0x54
> [13440.876491]  [<c02029ef>] default_idle+0x3b/0x54
> [13440.881211]  [<c0204c33>] apic_timer_interrupt+0x33/0x38
> [13440.886624]  [<c02029ef>] default_idle+0x3b/0x54
> [13440.891342]  [<c02029f1>] default_idle+0x3d/0x54
> [13440.896061]  [<c0202aaa>] cpu_idle+0xa2/0xbb
> [13440.900436]  =======================
> [13768.711447] BUG: spinlock lockup on CPU#1, swapper/0, c0687880
> [13768.717353]  [<c031f919>] _raw_spin_lock+0xda/0xfd
> [13768.722247]  [<c051ad48>] _spin_lock_irqsave+0x39/0x41
> [13768.727486]  [<f899bff2>] ipoib_neigh_destructor+0xd0/0x132 [ib_ipoib]
> [13768.734110]  [<f899bff2>] ipoib_neigh_destructor+0xd0/0x132 [ib_ipoib]
> [13768.740735]  [<c04a1c1b>] dst_run_gc+0xc/0x118
> [13768.745276]  [<c022af6e>] run_timer_softirq+0x37/0x16b
> [13768.750517]  [<c04a1c0f>] dst_run_gc+0x0/0x118
> [13768.755061]  [<c04a3eab>] neigh_destroy+0xbe/0x104
> [13768.759955]  [<c04a1bb1>] dst_destroy+0x4d/0xab
> [13768.764586]  [<c04a1c64>] dst_run_gc+0x55/0x118
> [13768.769218]  [<c022b03f>] run_timer_softirq+0x108/0x16b
> [13768.774542]  [<c0227634>] __do_softirq+0x5a/0xd5
> [13768.779261]  [<c023b435>] trace_hardirqs_on+0x106/0x141
> [13768.784588]  [<c0227643>] __do_softirq+0x69/0xd5
> [13768.789308]  [<c02276e6>] do_softirq+0x37/0x4d
> [13768.793851]  [<c02167b0>] smp_apic_timer_interrupt+0x6b/0x77
> [13768.799609]  [<c02029ef>] default_idle+0x3b/0x54
> [13768.804326]  [<c02029ef>] default_idle+0x3b/0x54
> [13768.809054]  [<c0204c33>] apic_timer_interrupt+0x33/0x38
> [13768.814471]  [<c02029ef>] default_idle+0x3b/0x54
> [13768.819187]  [<c02029f1>] default_idle+0x3d/0x54
> [13768.823903]  [<c0202aaa>] cpu_idle+0xa2/0xbb
> [13768.828279]  =======================
> 
> 
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