[PATCH net-next v2] net: lan743x: Don't sleep in atomic context

[PATCH net-next v2] net: lan743x: Don't sleep in atomic context

[Moritz Fischer]

dev_set_rx_mode() grabs a spin_lock, and the lan743x implementation
proceeds subsequently to go to sleep using readx_poll_timeout().

Introduce a helper wrapping the readx_poll_timeout_atomic() function
and use it to replace the calls to readx_polL_timeout().

Signed-off-by: Moritz Fischer <moritzf@google.com>
---

Changes from v1:
- Added line-breaks
- Changed subject to target net-next
- Removed Tested-by: tag

---
 drivers/net/ethernet/microchip/lan743x_main.c | 22 +++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
index f1bded993edc..4f277ffff1dc 100644
--- a/drivers/net/ethernet/microchip/lan743x_main.c
+++ b/drivers/net/ethernet/microchip/lan743x_main.c
@@ -144,6 +144,19 @@ static int lan743x_csr_light_reset(struct lan743x_adapter *adapter)
 				  !(data & HW_CFG_LRST_), 100000, 10000000);
 }
 
+static int lan743x_csr_wait_for_bit_atomic(struct lan743x_adapter *adapter,
+					   int offset, u32 bit_mask,
+					   int target_value, int udelay_min,
+					   int udelay_max, int count)
+{
+	u32 data;
+
+	return readx_poll_timeout_atomic(LAN743X_CSR_READ_OP, offset, data,
+					 target_value == ((data & bit_mask) ?
+					 1 : 0), udelay_max,
+					 udelay_min * count);
+}
+
 static int lan743x_csr_wait_for_bit(struct lan743x_adapter *adapter,
 				    int offset, u32 bit_mask,
 				    int target_value, int usleep_min,
@@ -736,8 +749,8 @@ static int lan743x_dp_write(struct lan743x_adapter *adapter,
 	u32 dp_sel;
 	int i;
 
-	if (lan743x_csr_wait_for_bit(adapter, DP_SEL, DP_SEL_DPRDY_,
-				     1, 40, 100, 100))
+	if (lan743x_csr_wait_for_bit_atomic(adapter, DP_SEL, DP_SEL_DPRDY_,
+					    1, 40, 100, 100))
 		return -EIO;
 	dp_sel = lan743x_csr_read(adapter, DP_SEL);
 	dp_sel &= ~DP_SEL_MASK_;
@@ -748,8 +761,9 @@ static int lan743x_dp_write(struct lan743x_adapter *adapter,
 		lan743x_csr_write(adapter, DP_ADDR, addr + i);
 		lan743x_csr_write(adapter, DP_DATA_0, buf[i]);
 		lan743x_csr_write(adapter, DP_CMD, DP_CMD_WRITE_);
-		if (lan743x_csr_wait_for_bit(adapter, DP_SEL, DP_SEL_DPRDY_,
-					     1, 40, 100, 100))
+		if (lan743x_csr_wait_for_bit_atomic(adapter, DP_SEL,
+						    DP_SEL_DPRDY_,
+						    1, 40, 100, 100))
 			return -EIO;
 	}
 
-- 
2.41.0.178.g377b9f9a00-goog

Re: [PATCH net-next v2] net: lan743x: Don't sleep in atomic context

[Jakub Kicinski]

On Sun, 25 Jun 2023 18:23:27 +0000 Moritz Fischer wrote:
> dev_set_rx_mode() grabs a spin_lock, and the lan743x implementation
> proceeds subsequently to go to sleep using readx_poll_timeout().
> 
> Introduce a helper wrapping the readx_poll_timeout_atomic() function
> and use it to replace the calls to readx_polL_timeout().
> 
> Signed-off-by: Moritz Fischer <moritzf@google.com>
> ---
> 
> Changes from v1:
> - Added line-breaks
> - Changed subject to target net-next
> - Removed Tested-by: tag

Sleeping in atomic context is a bug, this is a bug fix.
You should add a Fixes tag (probably 23f0703c125be AFAICT)
and target the patch at net rather than net-next.
Make sure you CC the authors of the patch under fixes (get_maintainer
will point them out if run on a patch file with a Fixes tag)
One more nit below...

>  drivers/net/ethernet/microchip/lan743x_main.c | 22 +++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/microchip/lan743x_main.c b/drivers/net/ethernet/microchip/lan743x_main.c
> index f1bded993edc..4f277ffff1dc 100644
> --- a/drivers/net/ethernet/microchip/lan743x_main.c
> +++ b/drivers/net/ethernet/microchip/lan743x_main.c
> @@ -144,6 +144,19 @@ static int lan743x_csr_light_reset(struct lan743x_adapter *adapter)
>  				  !(data & HW_CFG_LRST_), 100000, 10000000);
>  }
>  
> +static int lan743x_csr_wait_for_bit_atomic(struct lan743x_adapter *adapter,
> +					   int offset, u32 bit_mask,
> +					   int target_value, int udelay_min,
> +					   int udelay_max, int count)
> +{
> +	u32 data;
> +
> +	return readx_poll_timeout_atomic(LAN743X_CSR_READ_OP, offset, data,
> +					 target_value == ((data & bit_mask) ?
> +					 1 : 0), udelay_max,

You can save the awkward wrapping by using a double negation:

					target_value == !!(data & bit_mask)

this is a fairly common form in the kernel.
-- 
pw-bot: cr