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

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Date:	Tue, 5 Feb 2013 10:40:03 +0800
From:	Frank Li <lznuaa@...il.com>
To:	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>
Cc:	netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/1] net: fec: fix miss init spinlock

2013/2/5 Dmitry Eremin-Solenikov <dbaryshkov@...il.com>:
> 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.

Yes, you are right.

>
> --
> With best wishes
> Dmitry
>
>
> --
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