tg3: possible irq lock inversion dependency detected

[Nishanth Aravamudan]

Running 3.9-rc7-ish, tripped the following (also being seen in FC19
alpha) on ppc64:

[  117.026196] =========================================================
[  117.026216] [ INFO: possible irq lock inversion dependency detected ]
[  117.026238] 3.9.0-rc7+ #8 Not tainted
[  117.026251] ---------------------------------------------------------
[  117.026271] swapper/7/0 just changed the state of lock:
[  117.026286]  (&(&tp->lock)->rlock){+.-...}, at: [<c00000000064effc>] .tg3_timer+0x9c/0x10f0
[  117.026334] but this lock took another, SOFTIRQ-unsafe lock in the past:
[  117.026353]  (devtree_lock){+.+...}
 
and interrupts could create inverse lock ordering between them.
 
[  117.026389]
other info that might help us debug this:
[  117.026409] Chain exists of:
  &(&tp->lock)->rlock --> pci_lock --> devtree_lock
 
[  117.026452]  Possible interrupt unsafe locking scenario:
 
[  117.026472]        CPU0                    CPU1
[  117.026488]        ----                    ----
[  117.026503]   lock(devtree_lock);
[  117.026521]                                local_irq_disable();
[  117.026540]                                lock(&(&tp->lock)->rlock);
[  117.026567]                                lock(pci_lock);
[  117.026591]   <Interrupt>
[  117.026600]     lock(&(&tp->lock)->rlock);
[  117.026621]
 *** DEADLOCK ***
 
[  117.026644] 1 lock held by swapper/7/0:
[  117.026657]  #0:  ((&tp->timer)){+.-...}, at: [<c0000000000bbc50>] .call_timer_fn+0x0/0x3e0
[  117.026698]
the shortest dependencies between 2nd lock and 1st lock:
[  117.026722]   -> (devtree_lock){+.+...} ops: 13864154431488 {
[  117.026758]      HARDIRQ-ON-W at:
[  117.026772]      SOFTIRQ-ON-W at:
[  117.026786]      INITIAL USE at:
[  117.026799]    }
[  117.026809]    ... key      at: [<c00000000159b208>] devtree_lock+0x18/0x48
[  117.026835]    ... acquired at:
 
[  117.026857]  -> (pci_lock){......} ops: 3955664879616 {
[  117.026893]     INITIAL USE at:
[  117.026906]   }
[  117.026915]   ... key      at: [<c00000000157abe8>] pci_lock+0x18/0x48
[  117.026942]   ... acquired at:
 
[  117.026963] -> (&(&tp->lock)->rlock){+.-...} ops: 154618822656 {
[  117.027001]    HARDIRQ-ON-W at:
[  117.027015]    IN-SOFTIRQ-W at:
[  117.027029]    INITIAL USE at:
[  117.027042]  }
[  117.027051]  ... key      at: [<c0000000023a0311>] __key.48770+0x0/0x8
[  117.027078]  ... acquired at:
 
[  117.027100]
stack backtrace:
[  117.027116] Call Trace:
[  117.027129] [c0000003a7c7ad10] [c000000000016ee0] .show_stack+0xd0/0x1f0 (unreliable)
[  117.027161] [c0000003a7c7ade0] [c000000000137d78] .print_irq_inversion_bug+0x298/0x2f0
[  117.027189] [c0000003a7c7ae80] [c000000000137e70] .check_usage_forwards+0xa0/0x150
[  117.027217] [c0000003a7c7af70] [c000000000138b68] .mark_lock+0x258/0x7b0
[  117.027242] [c0000003a7c7b030] [c0000000001396f8] .__lock_acquire+0x638/0x1c20
[  117.027270] [c0000003a7c7b1b0] [c00000000013b480] .lock_acquire+0xb0/0x250
[  117.027296] [c0000003a7c7b290] [c00000000093a1cc] ._raw_spin_lock+0x5c/0xc0
[  117.027321] [c0000003a7c7b320] [c00000000064effc] .tg3_timer+0x9c/0x10f0
[  117.027345] [c0000003a7c7b3d0] [c0000000000bbd0c] .call_timer_fn+0xbc/0x3e0
[  117.027369] [c0000003a7c7b4b0] [c0000000000bc328] .run_timer_softirq+0x2f8/0x440
[  117.027398] [c0000003a7c7b5c0] [c0000000000afef8] .__do_softirq+0x1b8/0x540
[  117.027423] [c0000003a7c7b6f0] [c0000000000b04e8] .irq_exit+0xe8/0x100
[  117.027448] [c0000003a7c7b770] [c000000000020464] .timer_interrupt+0x174/0x510
[  117.027477] [c0000003a7c7b830] [c0000000000024f4] decrementer_common+0x174/0x180
[  117.027509] --- Exception: 901 at .plpar_hcall_norets+0x84/0xd4
    LR = .check_and_cede_processor+0x48/0x80
[  117.027544] [c0000003a7c7bb20] [c000000000085168] .check_and_cede_processor+0x18/0x80 (unreliable)
[  117.027577] [c0000003a7c7bb90] [c000000000085258] .dedicated_cede_loop+0x88/0x150
[  117.027606] [c0000003a7c7bc50] [c00000000075808c] .cpuidle_enter+0x2c/0x40
[  117.027632] [c0000003a7c7bcc0] [c0000000007589bc] .cpuidle_idle_call+0xfc/0x4e0
[  117.027660] [c0000003a7c7bd70] [c000000000074be8] .pSeries_idle+0x18/0x40
[  117.027685] [c0000003a7c7bde0] [c000000000018ec0] .cpu_idle+0x180/0x360
[  117.027711] [c0000003a7c7bea0] [c00000000095391c] .start_secondary+0x534/0x53c
[  117.027739] [c0000003a7c7bf90] [c0000000000097fc] .start_secondary_prolog+0x10/0x14

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