On Tue, Jan 17, 2023 at 05:18:19PM +0300, Dan Carpenter wrote:
> Hello Andrew Lunn,
Adding Florian
> The patch 4e4aafcddbbf: "net: mdio: Add dedicated C45 API to MDIO bus
> drivers" from Jan 9, 2023, leads to the following Smatch static
> checker warning:
>
> drivers/net/phy/mdio_bus.c:1003 mdiobus_c45_read() warn: sleeping in atomic context
> drivers/net/phy/mdio_bus.c:1104 mdiobus_c45_write() warn: sleeping in atomic context
>
> drivers/net/phy/mdio_bus.c
> 993 * @regnum: register number to read
> 994 *
> 995 * NOTE: MUST NOT be called from interrupt context,
> 996 * because the bus read/write functions may wait for an interrupt
> 997 * to conclude the operation.
> 998 */
> 999 int mdiobus_c45_read(struct mii_bus *bus, int addr, int devad, u32 regnum)
> 1000 {
> 1001 int retval;
> 1002
> --> 1003 mutex_lock(&bus->mdio_lock);
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> This takes a mutex.
>
> 1004 retval = __mdiobus_c45_read(bus, addr, devad, regnum);
> 1005 mutex_unlock(&bus->mdio_lock);
> 1006
> 1007 return retval;
> 1008 }
>
> The problematic call tree is:
>
> b44_ioctl() <- disables preempt
> -> phy_mii_ioctl()
> -> mdiobus_c45_read()
This seems like an old bug which my change has brought to light. I
believe MDIO operations have always been blocking. So i would say
b44_ioctl should not be taking a spinlock here.
Andrew
