netdev - Re: cassini: possible recursive locking detected

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Date:	Thu, 8 May 2014 23:00:03 +0300 (EEST)
From:	Meelis Roos <mroos@...ux.ee>
To:	Emil Goode <emilgoode@...il.com>
cc:	netdev@...r.kernel.org
Subject: Re: cassini: possible recursive locking detected

> Hello Meelis,
> 
> I think this warning happens because we acquire multiple locks
> in a loop in cas_lock_tx() and I believe we should use nested
> lock annotation here.
> 
> Perhaps you would like to try the attached patch?

Yes, it silences the warning.

> It won't fix the deadlock that you mentioned though.

Yes, the hang still happens, following a
ERROR: System Hardware FATAL RESET from  CPU0 CPU2

> 
> Best regards,
> 
> Emil Goode
> 
> On Tue, May 06, 2014 at 12:39:48PM +0300, Meelis Roos wrote:
> > While installing Linux on Sun Fire V480, any traffic on builtin cassini 
> > NIC caused a hang. Worked this around by using Broadcom NIC and tried a 
> > kernel with most debugging options. This resulted in the following 
> > warning. Maybe this is the deadlonck I was seeing?
> > 
> > [   88.316595] =============================================
> > [   88.316597] [ INFO: possible recursive locking detected ]
> > [   88.316603] 3.15.0-rc4-00202-g30321c7-dirty #11 Not tainted
> > [   88.316605] ---------------------------------------------
> > [   88.316608] swapper/3/1 is trying to acquire lock:
> > [   88.316644]  (&(&cp->tx_lock[i])->rlock){..-...}, at: [<0000000000745da0>] cas_link_timer+0xa0/0x460
> > [   88.316646]
> > [   88.316646] but task is already holding lock:
> > [   88.316657]  (&(&cp->tx_lock[i])->rlock){..-...}, at: [<0000000000745da0>] cas_link_timer+0xa0/0x460
> > [   88.316659]
> > [   88.316659] other info that might help us debug this:
> > [   88.316661]  Possible unsafe locking scenario:
> > [   88.316661]
> > [   88.316662]        CPU0
> > [   88.316664]        ----
> > [   88.316668]   lock(&(&cp->tx_lock[i])->rlock);
> > [   88.316671]   lock(&(&cp->tx_lock[i])->rlock);
> > [   88.316672]
> > [   88.316672]  *** DEADLOCK ***
> > [   88.316672]
> > [   88.316674]  May be due to missing lock nesting notation
> > [   88.316674]
> > [   88.316677] 3 locks held by swapper/3/1:
> > [   88.316694]  #0:  ((&cp->link_timer)){+.-...}, at: [<0000000000465f80>] call_timer_fn+0x0/0xe0
> > [   88.316706]  #1:  (&(&cp->lock)->rlock){..-...}, at: [<0000000000745d80>] cas_link_timer+0x80/0x460
> > [   88.316716]  #2:  (&(&cp->tx_lock[i])->rlock){..-...}, at: [<0000000000745da0>] cas_link_timer+0xa0/0x460
> > [   88.316718]
> > [   88.316718] stack backtrace:
> > [   88.316724] CPU: 2 PID: 1 Comm: swapper/3 Not tainted 3.15.0-rc4-00202-g30321c7-dirty #11
> > [   88.316727] Call Trace:
> > [   88.316743]  [00000000004a2c5c] __lock_acquire+0x10fc/0x1fa0
> > [   88.316749]  [00000000004a406c] lock_acquire+0x4c/0x80
> > [   88.316760]  [000000000083e07c] _raw_spin_lock+0x1c/0x40
> > [   88.316765]  [0000000000745da0] cas_link_timer+0xa0/0x460
> > [   88.316769]  [0000000000465fc8] call_timer_fn+0x48/0xe0
> > [   88.316775]  [00000000004665d4] run_timer_softirq+0x214/0x280
> > [   88.316788]  [000000000045f650] __do_softirq+0xf0/0x240
> > [   88.316800]  [000000000042bd0c] do_softirq_own_stack+0x2c/0x40
> > [   88.316804]  [000000000045fb44] irq_exit+0xc4/0xe0
> > [   88.316814]  [000000000042fcc8] timer_interrupt+0x88/0xc0
> > [   88.316819]  [0000000000426b84] valid_addr_bitmap_patch+0xbc/0x238
> > [   88.316826]  [00000000004ab2f8] vprintk_emit+0x1d8/0x540
> > [   88.316842]  [0000000000835fb8] printk+0x34/0x48
> > [   88.316847]  [00000000004ac3e0] register_console+0x340/0x3e0
> > [   88.316862]  [0000000000a74f2c] init_netconsole+0x180/0x20c
> > [   88.316867]  [0000000000426eb0] do_one_initcall+0x110/0x1a0
> > 
> > -- 
> > Meelis Roos (mroos@...ux.ee)
> > --
> > To unsubscribe from this list: send the line "unsubscribe netdev" in
> > the body of a message to majordomo@...r.kernel.org
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> 

-- 
Meelis Roos (mroos@...ux.ee)
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