Subject: Re: [PATCH] ks8851: Fix missing mutex_lock/unlock

From: Stephen Boyd <[email-masked]>
Date: Thu, 12 Apr 2012 13:34:32 -0700

On 04/12/12 13:06, [email-masked] wrote:
> From: Matt Renzelmann <[email-masked]>
>
> All calls to ks8851_rdreg* and ks8851_wrreg* should be protected with
> the driver's lock mutex.  A spurious interrupt may otherwise cause a
> crash.
>
> Signed-off-by: Matt Renzelmann <[email-masked]>
> ---
>
> Thank you, Mr. Leitner, for providing feedback.  I agree with your
> changes and have updated the patch to reflect them.  I apologize for
> missing the driver name in the title -- I've updated the patch with
> that information as well.  Please let me know if there is anything
> else I should fix/change.
>
>  drivers/net/ethernet/micrel/ks8851.c |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/micrel/ks8851.c b/drivers/net/ethernet/micrel/ks8851.c
> index c722aa6..20237dc 100644
> --- a/drivers/net/ethernet/micrel/ks8851.c
> +++ b/drivers/net/ethernet/micrel/ks8851.c
> @@ -1417,6 +1417,7 @@ static int __devinit ks8851_probe(struct spi_device *spi)
>  {
>  	struct net_device *ndev;
>  	struct ks8851_net *ks;
> +	int result;
>  	int ret;
>  
>  	ndev = alloc_etherdev(sizeof(struct ks8851_net));
> @@ -1515,9 +1516,12 @@ static int __devinit ks8851_probe(struct spi_device *spi)
>  		goto err_netdev;
>  	}
>  
> +	mutex_lock(&ks->lock);
> +	result = CIDER_REV_GET(ks8851_rdreg16(ks, KS_CIDER));
> +	mutex_unlock(&ks->lock);
> +
>  	netdev_info(ndev, "revision %d, MAC %pM, IRQ %d, %s EEPROM\n",
> -		    CIDER_REV_GET(ks8851_rdreg16(ks, KS_CIDER)),
> -		    ndev->dev_addr, ndev->irq,
> +		    result, ndev->dev_addr, ndev->irq,
>  		    ks->rc_ccr & CCR_EEPROM ? "has" : "no");
>  
>  	return 0;

This register is already read in the probe function and the lock is not
held there so you seem to have missed a couple. I would guess it doesn't
really matter tha we don't grab the lock though because the device isn't
actively sending/receiving packets. How about this instead?

diff --git a/drivers/net/ethernet/micrel/ks8851.c b/drivers/net/ethernet/micrel/ks8851.c
index c722aa60..6f21fcd 100644
--- a/drivers/net/ethernet/micrel/ks8851.c
+++ b/drivers/net/ethernet/micrel/ks8851.c
@@ -1418,6 +1418,7 @@ static int __devinit ks8851_probe(struct spi_device *spi)
        struct net_device *ndev;
        struct ks8851_net *ks;
        int ret;
+       unsigned cider;
 
        ndev = alloc_etherdev(sizeof(struct ks8851_net));
        if (!ndev)
@@ -1484,8 +1485,9 @@ static int __devinit ks8851_probe(struct spi_device *spi)
        ks8851_soft_reset(ks, GRR_GSR);
 
        /* simple check for a valid chip being connected to the bus */
-
-       if ((ks8851_rdreg16(ks, KS_CIDER) & ~CIDER_REV_MASK) != CIDER_ID) {
+       mutex_lock(&ks->lock);
+       cider = ks8851_rdreg16(ks, KS_CIDER);
+       if ((cider & ~CIDER_REV_MASK) != CIDER_ID) {
                dev_err(&spi->dev, "failed to read device ID\n");
                ret = -ENODEV;
                goto err_id;
@@ -1493,6 +1495,7 @@ static int __devinit ks8851_probe(struct spi_device *spi)
 
        /* cache the contents of the CCR register for EEPROM, etc. */
        ks->rc_ccr = ks8851_rdreg16(ks, KS_CCR);
+       mutex_unlock(&ks->lock);
 
        if (ks->rc_ccr & CCR_EEPROM)
                ks->eeprom_size = 128;
@@ -1516,8 +1519,7 @@ static int __devinit ks8851_probe(struct spi_device *spi)
        }
 
        netdev_info(ndev, "revision %d, MAC %pM, IRQ %d, %s EEPROM\n",
-                   CIDER_REV_GET(ks8851_rdreg16(ks, KS_CIDER)),
-                   ndev->dev_addr, ndev->irq,
+                   CIDER_REV_GET(cider), ndev->dev_addr, ndev->irq,
                    ks->rc_ccr & CCR_EEPROM ? "has" : "no");
 
        return 0;

-- 
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