netdev - Re: [PATCH 1/1] net: fec: fix miss init spinlock

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Date:	Mon, 4 Feb 2013 23:23:28 +0000 (UTC)
From:	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>
To:	netdev@...r.kernel.org
Cc:	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/1] net: fec: fix miss init spinlock

On Fri, 01 Feb 2013 16:56:26 +0800, Frank Li wrote:

> BUG: spinlock bad magic on CPU#1, swapper/0/1 lock: 0xbfae0f8c, .magic:
> 00000000, .owner: <none>/-1, .owner_cpu: 0 Backtrace:
>  [<80011d54>] (dump_backtrace+0x0/0x10c) from [<804e7800>]
>  (dump_stack+0x18/0x1c)
>  r6:bfae0000 r5:bfae0f8c r4:00000000 r3:806c1310 [<804e77e8>]
>  (dump_stack+0x0/0x1c) from [<804e9f20>] (spin_dump+0x80/0x94)
>  [<804e9ea0>] (spin_dump+0x0/0x94) from [<804e9f60>]
>  (spin_bug+0x2c/0x30)
>  r5:805f6f8c r4:bfae0f8c [<804e9f34>] (spin_bug+0x0/0x30) from
>  [<80257984>] (do_raw_spin_lock+0x170/0x1b0                             
>             )
>  r5:806b4950 r4:bfae0f8c [<80257814>] (do_raw_spin_lock+0x0/0x1b0) from
>  [<804ed15c>] (_raw_spin_lock_irqs                                      
>    ave+0x18/0x20) [<804ed144>] (_raw_spin_lock_irqsave+0x0/0x20) from
>  [<8033c694>] (fec_ptp_start_                                        
>  cyclecounter+0x3c/0x120)
>  r4:bfae0f8c r3:00000002 [<8033c658>]
>  (fec_ptp_start_cyclecounter+0x0/0x120) from [<80339e08>] (fec_resta    
>                                      rt+0x56c/0x5f8) r8:00000000
>  r7:806e6f48 r6:00000112 r5:806b4950 r4:bfae0000 [<8033989c>]
>  (fec_restart+0x0/0x5f8) from [<8033b9e4>] (fec_probe+0x508/0xa48)
> 
> Signed-off-by: Frank Li <Frank.Li@...escale.com>
> ---
>  drivers/net/ethernet/freescale/fec.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fec.c
> b/drivers/net/ethernet/freescale/fec.c index 69b16b9..f900ae4 100644 ---
> a/drivers/net/ethernet/freescale/fec.c +++
> b/drivers/net/ethernet/freescale/fec.c @@ -1607,6 +1607,7 @@ static int
> fec_enet_init(struct net_device *ndev)
>  	}
>  
>  	spin_lock_init(&fep->hw_lock);
> +	spin_lock_init(&fep->tmreg_lock);
>  
>  	fep->netdev = ndev;

Please excuse me, if I'm wrong. I would consider this as a very wrong 
solution:

First, then the spin lock is initialised twice (first time in 
fec_enet_init(), second time in fec_ptp_init()).

Then this patch actually hides the fact that PTP part of fec
is accessed from fec_ptp_start_cyclecounter() way before
than fec_ptp_init() is called to initialize PTP).

In my opinion the right patch should either move fec_ptp_init() call 
before fec_restart(), or make fec_restart intelelctual about calling
fec_ptp_init()/fec_ptp_startcyclecounter() at proper time.

-- 
With best wishes
Dmitry


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