netdev - Re: cassini: possible recursive locking detected

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Date:	Thu, 8 May 2014 14:53:36 +0200
From:	Emil Goode <emilgoode@...il.com>
To:	Meelis Roos <mroos@...ux.ee>
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?

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

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)
> --
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View attachment "0001-net-cassini-use-nested-lock-annotation.patch" of type "text/x-diff" (937 bytes)