Patchwork [1/2] mrf24j40: Avoid transmission while receiving a frame

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Submitter David Hauweele
Date May 9, 2013, 3:19 p.m.
Message ID <1368112788-25701-1-git-send-email-david@hauweele.net>
Download mbox | patch
Permalink /patch/242769/
State Changes Requested
Delegated to: David Miller
Headers show

Comments

David Hauweele - May 9, 2013, 3:19 p.m.
The transceiver may fail under heavy traffic when a frame is transmitted
while receiving another frame.

This patch uses a mutex to separate the transmission and reception of
frames along with a secondary working queue to avoid a deadlock while
waiting for the transmission interrupt.

Signed-off-by: David Hauweele <david@hauweele.net>
---
 drivers/net/ieee802154/mrf24j40.c |   22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)
Alan Ott - May 14, 2013, 3:22 a.m.
On 5/9/13 11:19 AM, David Hauweele wrote:
> The transceiver may fail under heavy traffic when a frame is transmitted
> while receiving another frame.
>
> This patch uses a mutex to separate the transmission and reception of
> frames along with a secondary working queue to avoid a deadlock while
> waiting for the transmission interrupt.
>

Have you observed this failure? I have put this kind of thing in before 
(several times actually) but ultimately convinced myself each time that 
it was not necessary. I'm happy to be shown wrong.


> Signed-off-by: David Hauweele <david@hauweele.net>
> ---
>   drivers/net/ieee802154/mrf24j40.c |   22 +++++++++++++++++++++-
>   1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ieee802154/mrf24j40.c b/drivers/net/ieee802154/mrf24j40.c
> index ede3ce4..1e3ddf3 100644
> --- a/drivers/net/ieee802154/mrf24j40.c
> +++ b/drivers/net/ieee802154/mrf24j40.c
> @@ -82,8 +82,10 @@ struct mrf24j40 {
>   	struct ieee802154_dev *dev;
>
>   	struct mutex buffer_mutex; /* only used to protect buf */
> +	struct mutex txrx_mutex; /* avoid transmission while receiving a frame */
>   	struct completion tx_complete;
>   	struct work_struct irqwork;
> +	struct work_struct rxwork;
>   	u8 *buf; /* 3 bytes. Used for SPI single-register transfers. */
>   };
>
> @@ -353,6 +355,8 @@ static int mrf24j40_tx(struct ieee802154_dev *dev, struct sk_buff *skb)
>   	/* Set TXNACKREQ if the ACK bit is set in the packet. */
>   	if (skb->data[0] & IEEE802154_FC_ACK_REQ)
>   		val |= 0x4;
> +
> +	mutex_lock(&devrec->txrx_mutex);
>   	write_short_reg(devrec, REG_TXNCON, val);
>
>   	INIT_COMPLETION(devrec->tx_complete);
> @@ -361,6 +365,9 @@ static int mrf24j40_tx(struct ieee802154_dev *dev, struct sk_buff *skb)
>   	ret = wait_for_completion_interruptible_timeout(
>   						&devrec->tx_complete,
>   						5 * HZ);
> +
> +	mutex_unlock(&devrec->txrx_mutex);
> +
>   	if (ret == -ERESTARTSYS)
>   		goto err;
>   	if (ret == 0) {
> @@ -535,6 +542,8 @@ static int mrf24j40_handle_rx(struct mrf24j40 *devrec)
>   	int ret = 0;
>   	struct sk_buff *skb;
>
> +	mutex_lock(&devrec->txrx_mutex);
> +
>   	/* Turn off reception of packets off the air. This prevents the
>   	 * device from overwriting the buffer while we're reading it. */
>   	ret = read_short_reg(devrec, REG_BBREG1, &val);
> @@ -575,6 +584,8 @@ out:
>   	val &= ~0x4; /* Clear RXDECINV */
>   	write_short_reg(devrec, REG_BBREG1, val);
>
> +	mutex_unlock(&devrec->txrx_mutex);
> +
>   	return ret;
>   }
>
> @@ -616,12 +627,19 @@ static void mrf24j40_isrwork(struct work_struct *work)
>
>   	/* Check for Rx */
>   	if (intstat & 0x8)
> -		mrf24j40_handle_rx(devrec);
> +		schedule_work(&devrec->rxwork);
>

mrf24f40_isrwork() is already called from a workqueue.

>   out:
>   	enable_irq(devrec->spi->irq);
>   }
>
> +static void mrf24j40_rxwork(struct work_struct *work)
> +{
> +	struct mrf24j40 *devrec = container_of(work, struct mrf24j40, rxwork);
> +
> +	mrf24j40_handle_rx(devrec);
> +}
> +
>   static int mrf24j40_probe(struct spi_device *spi)
>   {
>   	int ret = -ENOMEM;
> @@ -648,8 +666,10 @@ static int mrf24j40_probe(struct spi_device *spi)
>   		spi->max_speed_hz = MAX_SPI_SPEED_HZ;
>
>   	mutex_init(&devrec->buffer_mutex);
> +	mutex_init(&devrec->txrx_mutex);
>   	init_completion(&devrec->tx_complete);
>   	INIT_WORK(&devrec->irqwork, mrf24j40_isrwork);
> +	INIT_WORK(&devrec->rxwork, mrf24j40_rxwork);
>   	devrec->spi = spi;
>   	spi_set_drvdata(spi, devrec);
>
>

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Patch

diff --git a/drivers/net/ieee802154/mrf24j40.c b/drivers/net/ieee802154/mrf24j40.c
index ede3ce4..1e3ddf3 100644
--- a/drivers/net/ieee802154/mrf24j40.c
+++ b/drivers/net/ieee802154/mrf24j40.c
@@ -82,8 +82,10 @@  struct mrf24j40 {
 	struct ieee802154_dev *dev;
 
 	struct mutex buffer_mutex; /* only used to protect buf */
+	struct mutex txrx_mutex; /* avoid transmission while receiving a frame */
 	struct completion tx_complete;
 	struct work_struct irqwork;
+	struct work_struct rxwork;
 	u8 *buf; /* 3 bytes. Used for SPI single-register transfers. */
 };
 
@@ -353,6 +355,8 @@  static int mrf24j40_tx(struct ieee802154_dev *dev, struct sk_buff *skb)
 	/* Set TXNACKREQ if the ACK bit is set in the packet. */
 	if (skb->data[0] & IEEE802154_FC_ACK_REQ)
 		val |= 0x4;
+
+	mutex_lock(&devrec->txrx_mutex);
 	write_short_reg(devrec, REG_TXNCON, val);
 
 	INIT_COMPLETION(devrec->tx_complete);
@@ -361,6 +365,9 @@  static int mrf24j40_tx(struct ieee802154_dev *dev, struct sk_buff *skb)
 	ret = wait_for_completion_interruptible_timeout(
 						&devrec->tx_complete,
 						5 * HZ);
+
+	mutex_unlock(&devrec->txrx_mutex);
+
 	if (ret == -ERESTARTSYS)
 		goto err;
 	if (ret == 0) {
@@ -535,6 +542,8 @@  static int mrf24j40_handle_rx(struct mrf24j40 *devrec)
 	int ret = 0;
 	struct sk_buff *skb;
 
+	mutex_lock(&devrec->txrx_mutex);
+
 	/* Turn off reception of packets off the air. This prevents the
 	 * device from overwriting the buffer while we're reading it. */
 	ret = read_short_reg(devrec, REG_BBREG1, &val);
@@ -575,6 +584,8 @@  out:
 	val &= ~0x4; /* Clear RXDECINV */
 	write_short_reg(devrec, REG_BBREG1, val);
 
+	mutex_unlock(&devrec->txrx_mutex);
+
 	return ret;
 }
 
@@ -616,12 +627,19 @@  static void mrf24j40_isrwork(struct work_struct *work)
 
 	/* Check for Rx */
 	if (intstat & 0x8)
-		mrf24j40_handle_rx(devrec);
+		schedule_work(&devrec->rxwork);
 
 out:
 	enable_irq(devrec->spi->irq);
 }
 
+static void mrf24j40_rxwork(struct work_struct *work)
+{
+	struct mrf24j40 *devrec = container_of(work, struct mrf24j40, rxwork);
+
+	mrf24j40_handle_rx(devrec);
+}
+
 static int mrf24j40_probe(struct spi_device *spi)
 {
 	int ret = -ENOMEM;
@@ -648,8 +666,10 @@  static int mrf24j40_probe(struct spi_device *spi)
 		spi->max_speed_hz = MAX_SPI_SPEED_HZ;
 
 	mutex_init(&devrec->buffer_mutex);
+	mutex_init(&devrec->txrx_mutex);
 	init_completion(&devrec->tx_complete);
 	INIT_WORK(&devrec->irqwork, mrf24j40_isrwork);
+	INIT_WORK(&devrec->rxwork, mrf24j40_rxwork);
 	devrec->spi = spi;
 	spi_set_drvdata(spi, devrec);