Subject: Re: tg3: possible irq lock inversion dependency detected

From: Nishanth Aravamudan <[email-masked]>
Date: Fri, 19 Apr 2013 15:21:55 -0700

Hi Rob,

On 19.04.2013 [14:23:21 -0500], Rob Herring wrote:
> On 04/19/2013 02:01 PM, Nishanth Aravamudan wrote:
> > 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
> > 
> 
> It might be related to this commit. Can you revert and try it.

With commit d6d3c4e656513dcea61ce900f0ecb9ca820ee7cd reverted, I do not see the
message above, but I do see:

[    1.457095] BUG: spinlock bad magic on CPU#0, swapper/0/1
[    1.457150]  lock: devtree_lock+0x0/0x48, .magic: deaf1eed, .owner: swapper/0/1, .owner_cpu: 0
[    1.457199] Call Trace:
[    1.457234] [c0000003a7983710] [c000000000016ee0] .show_stack+0xd0/0x1f0 (unreliable)
[    1.457302] [c0000003a79837e0] [c00000000094f284] .spin_dump+0x94/0xb0
[    1.457362] [c0000003a7983860] [c00000000049f104] .do_raw_spin_unlock+0x94/0xf0
[    1.457426] [c0000003a79838e0] [c00000000093b2b4] ._raw_spin_unlock_irqrestore+0x44/0xd0
[    1.457487] [c0000003a7983970] [c00000000077ddc8] .of_device_is_available+0x58/0x80
[    1.457551] [c0000003a7983a00] [c00000000007f4f8] .pseries_eeh_of_probe+0x48/0x350
[    1.457612] [c0000003a7983af0] [c00000000003f084] .traverse_pci_devices+0xa4/0x170
[    1.457678] [c0000003a7983b90] [c000000000ccd4a0] .eeh_init+0x104/0x170
[    1.457734] [c0000003a7983c20] [c00000000000b5d4] .do_one_initcall+0x174/0x1f0
[    1.457798] [c0000003a7983cd0] [c000000000cb502c] .kernel_init_freeable+0x224/0x314
[    1.457860] [c0000003a7983db0] [c00000000000bd94] .kernel_init+0x24/0x130
[    1.457917] [c0000003a7983e30] [c00000000000a1f0] .ret_from_kernel_thread+0x64/0x74

Thanks,
Nish
 
> Author: Thomas Gleixner <[email-masked]>
> Date:   Wed Feb 6 15:30:56 2013 -0500
> 
>     OF: convert devtree lock from rw_lock to raw spinlock
> 
>     With the locking cleanup in place (from "OF: Fixup resursive
>     locking code paths"), we can now do the conversion from the
>     rw_lock to a raw spinlock as required for preempt-rt.
> 
>     The previous cleanup and this conversion were originally
>     separate since they predated when mainline got raw spinlock (in
>     commit c2f21ce2e31286a "locking: Implement new raw_spinlock").
> 
>     So, at that point in time, the cleanup was considered plausible
>     for mainline, but not this conversion.  In any case, we've kept
>     them separate as it makes for easier review and better bisection.
> 
>     Signed-off-by: Thomas Gleixner <[email-masked]>
>     [PG: taken from preempt-rt, update subject & add a commit log]
>     Signed-off-by: Paul Gortmaker <[email-masked]>
>     Signed-off-by: Rob Herring <[email-masked]>
>