Re: [PATCH] can: sja1000_isa: add locking for indirect register access mode

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 04/15/2014 11:26 PM, Thomas Gleixner wrote:
> On Tue, 15 Apr 2014, Oliver Hartkopp wrote:
> 
>> When accessing the SJA1000 controller registers in the indirect access mode,
>> writing the register number and reading/writing the data has to be an atomic
>> attempt.
>>
>> As the sja1000_isa driver is an old style driver with a fixed number of
>> instances the locking variable depends on the same index like all the other
>> configuration elements given on the module command line.
>>
>> As a positive side effect dev->dev_id is populated by the instance index,
>> which was missing in 3e66d0138c05d9 ("can: populate netdev::dev_id for udev
>> discrimination").
>>
>> Reported-by: Marc Kleine-Budde <mkl@pengutronix.de>
>> Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
>>
>> ---
>>
>> diff --git a/drivers/net/can/sja1000/sja1000_isa.c b/drivers/net/can/sja1000/sja1000_isa.c
>> index df136a2..014695d 100644
>> --- a/drivers/net/can/sja1000/sja1000_isa.c
>> +++ b/drivers/net/can/sja1000/sja1000_isa.c
>> @@ -46,6 +46,7 @@ static int clk[MAXDEV];
>>  static unsigned char cdr[MAXDEV] = {[0 ... (MAXDEV - 1)] = 0xff};
>>  static unsigned char ocr[MAXDEV] = {[0 ... (MAXDEV - 1)] = 0xff};
>>  static int indirect[MAXDEV] = {[0 ... (MAXDEV - 1)] = -1};
>> +static spinlock_t indirect_lock[MAXDEV];  /* lock for indirect access mode */
> 
> You need to initialize the spinlock if you want to survive lockdep.
> 
> Either use the proper static initializer or do an explicit
> spin_lock_init() on each of the locks before using them.

There's a spin_lock_init in the probe function:

>  static int sja1000_isa_probe(struct platform_device *pdev)
> @@ -169,6 +177,7 @@ static int sja1000_isa_probe(struct platform_device *pdev)
>  		if (iosize == SJA1000_IOSIZE_INDIRECT) {
>  			priv->read_reg = sja1000_isa_port_read_reg_indirect;
>  			priv->write_reg = sja1000_isa_port_write_reg_indirect;
> +			spin_lock_init(&indirect_lock[idx]);
>  		} else {
>  			priv->read_reg = sja1000_isa_port_read_reg;
>  			priv->write_reg = sja1000_isa_port_write_reg;

Marc

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