linux-kernel - Re: [PATCH net-next] net: dsa: mv88e6xxx: assert SMI lock

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Message-ID: <20151030204110.GB10053@lunn.ch>
Date:	Fri, 30 Oct 2015 21:41:10 +0100
From:	Andrew Lunn <andrew@...n.ch>
To:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...oirfairelinux.com,
	"David S. Miller" <davem@...emloft.net>,
	Florian Fainelli <f.fainelli@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Neil Armstrong <narmstrong@...libre.com>
Subject: Re: [PATCH net-next] net: dsa: mv88e6xxx: assert SMI lock

On Fri, Oct 30, 2015 at 04:35:42PM -0400, Vivien Didelot wrote:
> It's easy to forget to lock the smi_mutex before calling the low-level
> _mv88e6xxx_reg_{read,write}, so add a assert_smi_lock function in them.
> 
> Signed-off-by: Vivien Didelot <vivien.didelot@...oirfairelinux.com>
> ---
>  drivers/net/dsa/mv88e6xxx.c | 31 ++++++++++++++++++-------------
>  1 file changed, 18 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/net/dsa/mv88e6xxx.c b/drivers/net/dsa/mv88e6xxx.c
> index b1b14f5..70a0106 100644
> --- a/drivers/net/dsa/mv88e6xxx.c
> +++ b/drivers/net/dsa/mv88e6xxx.c
> @@ -24,6 +24,16 @@
>  #include <net/switchdev.h>
>  #include "mv88e6xxx.h"
>  
> +static inline void assert_smi_lock(struct dsa_switch *ds)

No need for inline. Gcc will automatically inline it, if it thinks it
is small enough.

> +{
> +	struct mv88e6xxx_priv_state *ps = ds_to_priv(ds);
> +
> +	if (unlikely(!mutex_is_locked(&ps->smi_mutex))) {
> +		dev_err(ds->master_dev, "SMI lock not held!\n");
> +		dump_stack();
> +	}
> +}
> +

> -/* Must be called with SMI mutex held */
>  static int _mv88e6xxx_reg_read(struct dsa_switch *ds, int addr, int reg)
>  {
> -	struct mii_bus *bus = dsa_host_dev_to_mii_bus(ds->master_dev);
> +	struct mii_bus *bus;
>  	int ret;
>  
> +	assert_smi_lock(ds);
> +
> +	bus = dsa_host_dev_to_mii_bus(ds->master_dev);

Is this change of when bus is assigned actually required?

Thanks
	Andrew
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