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Commit 5988f385 authored by Quintin Pitts's avatar Quintin Pitts Committed by John W. Linville
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p54pci: prevent stuck rx-ring on slow system 

This patch fixes an old problem, which - under certain
circumstances - could cause the device to become
unresponsive.

most of p54pci's rx-ring management is implemented in just
two distinct standalone functions. p54p_check_rx_ring takes
care of processing incoming data, while p54p_refill_rx_ring
tries to replenish all depleted communication buffers.

This has always worked fine on my fast machine, but
now I know there is a hidden race...

The most likely candidate here is ring_control->device_idx.
Quintin Pitts had already analyzed the culprit and posted
a patch back in Oct 2009. But sadly, no one's picked up on this.
( https://patchwork.kernel.org/patch/53079/

 [2 & 3] ).
This patch does the same way, except that it also prioritize
rx data processing, simply because tx routines *can* wait.

Reported-by: default avatarSean Young <sean@mess.org>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=11386


Reported-by: default avatarQuintin Pitts <geek4linux@gmail.com>
Signed-off-by: default avatarQuintin Pitts <geek4linux@gmail.com>
Signed-off-by: default avatarChristian Lamparter <chunkeey@googlemail.com>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent b1f90866

drivers/net/wireless/p54/p54pci.c

+13 −13
Original line number Diff line number Diff line
@@ -131,7 +131,7 @@ static int p54p_upload_firmware(struct ieee80211_hw *dev) 


static void p54p_refill_rx_ring(struct ieee80211_hw *dev,

	int ring_index, struct p54p_desc *ring, u32 ring_limit,

	struct sk_buff **rx_buf)

	struct sk_buff **rx_buf, u32 index)

{

	struct p54p_priv *priv = dev->priv;

	struct p54p_ring_control *ring_control = priv->ring_control;
@@ -139,7 +139,7 @@ static void p54p_refill_rx_ring(struct ieee80211_hw *dev, 


	idx = le32_to_cpu(ring_control->host_idx[ring_index]);

	limit = idx;

	limit -= le32_to_cpu(ring_control->device_idx[ring_index]);

	limit -= le32_to_cpu(index);

	limit = ring_limit - limit;



	i = idx % ring_limit;
@@ -231,7 +231,7 @@ static void p54p_check_rx_ring(struct ieee80211_hw *dev, u32 *index, 
		i %= ring_limit;

	}



	p54p_refill_rx_ring(dev, ring_index, ring, ring_limit, rx_buf);

	p54p_refill_rx_ring(dev, ring_index, ring, ring_limit, rx_buf, *index);

}



static void p54p_check_tx_ring(struct ieee80211_hw *dev, u32 *index,
@@ -276,14 +276,6 @@ static void p54p_tasklet(unsigned long dev_id) 
	struct p54p_priv *priv = dev->priv;

	struct p54p_ring_control *ring_control = priv->ring_control;



	p54p_check_tx_ring(dev, &priv->tx_idx_mgmt, 3, ring_control->tx_mgmt,

			   ARRAY_SIZE(ring_control->tx_mgmt),

			   priv->tx_buf_mgmt);



	p54p_check_tx_ring(dev, &priv->tx_idx_data, 1, ring_control->tx_data,

			   ARRAY_SIZE(ring_control->tx_data),

			   priv->tx_buf_data);



	p54p_check_rx_ring(dev, &priv->rx_idx_mgmt, 2, ring_control->rx_mgmt,

		ARRAY_SIZE(ring_control->rx_mgmt), priv->rx_buf_mgmt);
@@ -292,6 +284,14 @@ static void p54p_tasklet(unsigned long dev_id) 


	wmb();

	P54P_WRITE(dev_int, cpu_to_le32(ISL38XX_DEV_INT_UPDATE));



	p54p_check_tx_ring(dev, &priv->tx_idx_mgmt, 3, ring_control->tx_mgmt,

			   ARRAY_SIZE(ring_control->tx_mgmt),

			   priv->tx_buf_mgmt);



	p54p_check_tx_ring(dev, &priv->tx_idx_data, 1, ring_control->tx_data,

			   ARRAY_SIZE(ring_control->tx_data),

			   priv->tx_buf_data);

}



static irqreturn_t p54p_interrupt(int irq, void *dev_id)
@@ -444,10 +444,10 @@ static int p54p_open(struct ieee80211_hw *dev) 
	priv->rx_idx_mgmt = priv->tx_idx_mgmt = 0;



	p54p_refill_rx_ring(dev, 0, priv->ring_control->rx_data,

		ARRAY_SIZE(priv->ring_control->rx_data), priv->rx_buf_data);

		ARRAY_SIZE(priv->ring_control->rx_data), priv->rx_buf_data, 0);



	p54p_refill_rx_ring(dev, 2, priv->ring_control->rx_mgmt,

		ARRAY_SIZE(priv->ring_control->rx_mgmt), priv->rx_buf_mgmt);

		ARRAY_SIZE(priv->ring_control->rx_mgmt), priv->rx_buf_mgmt, 0);



	P54P_WRITE(ring_control_base, cpu_to_le32(priv->ring_control_dma));

	P54P_READ(ring_control_base);