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[PATCH 1/4 net] qca_spi: Fix SPI thread creation

Stefan Wahren posted 4 patches 2 years ago
There is a newer version of this series
[PATCH 1/4 net] qca_spi: Fix SPI thread creation
Posted by Stefan Wahren 2 years ago 
The qca_spi driver create/stop the SPI kernel thread in case
of netdev_open/close. This is a big issue because it allows
userspace to prevent from restarting the SPI thread after
ring parameter changes (e.g. signals which stop the thread).
This could be done by terminating a script which changes
the ring parameter in a loop.

So fix this by moving create/stop of the SPI kernel into
the init/uninit ops. The open/close ops could be realized just
by 'park/unpark' the SPI kernel thread.

Fixes: 291ab06ecf67 ("net: qualcomm: new Ethernet over SPI driver for QCA7000")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
---
 drivers/net/ethernet/qualcomm/qca_spi.c | 35 ++++++++++++++++---------
 1 file changed, 23 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/qualcomm/qca_spi.c b/drivers/net/ethernet/qualcomm/qca_spi.c
index bec723028e96..b11a998b2456 100644
--- a/drivers/net/ethernet/qualcomm/qca_spi.c
+++ b/drivers/net/ethernet/qualcomm/qca_spi.c
@@ -580,6 +580,11 @@ qcaspi_spi_thread(void *data)
 	netdev_info(qca->net_dev, "SPI thread created\n");
 	while (!kthread_should_stop()) {
 		set_current_state(TASK_INTERRUPTIBLE);
+		if (kthread_should_park()) {
+			kthread_parkme();
+			continue;
+		}
+
 		if ((qca->intr_req == qca->intr_svc) &&
 		    !qca->txr.skb[qca->txr.head])
 			schedule();
@@ -679,25 +684,17 @@ qcaspi_netdev_open(struct net_device *dev)
 	qca->sync = QCASPI_SYNC_UNKNOWN;
 	qcafrm_fsm_init_spi(&qca->frm_handle);

-	qca->spi_thread = kthread_run((void *)qcaspi_spi_thread,
-				      qca, "%s", dev->name);
-
-	if (IS_ERR(qca->spi_thread)) {
-		netdev_err(dev, "%s: unable to start kernel thread.\n",
-			   QCASPI_DRV_NAME);
-		return PTR_ERR(qca->spi_thread);
-	}
-
 	ret = request_irq(qca->spi_dev->irq, qcaspi_intr_handler, 0,
 			  dev->name, qca);
 	if (ret) {
 		netdev_err(dev, "%s: unable to get IRQ %d (irqval=%d).\n",
 			   QCASPI_DRV_NAME, qca->spi_dev->irq, ret);
-		kthread_stop(qca->spi_thread);
 		return ret;
 	}

 	/* SPI thread takes care of TX queue */
+	kthread_unpark(qca->spi_thread);
+	wake_up_process(qca->spi_thread);

 	return 0;
 }
@@ -712,8 +709,7 @@ qcaspi_netdev_close(struct net_device *dev)
 	qcaspi_write_register(qca, SPI_REG_INTR_ENABLE, 0, wr_verify);
 	free_irq(qca->spi_dev->irq, qca);

-	kthread_stop(qca->spi_thread);
-	qca->spi_thread = NULL;
+	kthread_park(qca->spi_thread);
 	qcaspi_flush_tx_ring(qca);

 	return 0;
@@ -807,6 +803,7 @@ static int
 qcaspi_netdev_init(struct net_device *dev)
 {
 	struct qcaspi *qca = netdev_priv(dev);
+	struct task_struct *thread;

 	dev->mtu = QCAFRM_MAX_MTU;
 	dev->type = ARPHRD_ETHER;
@@ -830,6 +827,15 @@ qcaspi_netdev_init(struct net_device *dev)
 		return -ENOBUFS;
 	}

+	thread = kthread_create(qcaspi_spi_thread, qca, "%s", dev->name);
+	if (IS_ERR(thread)) {
+		netdev_err(dev, "%s: unable to start kernel thread.\n",
+			   QCASPI_DRV_NAME);
+		return PTR_ERR(thread);
+	}
+
+	qca->spi_thread = thread;
+
 	return 0;
 }

@@ -838,6 +844,11 @@ qcaspi_netdev_uninit(struct net_device *dev)
 {
 	struct qcaspi *qca = netdev_priv(dev);

+	if (qca->spi_thread) {
+		kthread_stop(qca->spi_thread);
+		qca->spi_thread = NULL;
+	}
+
 	kfree(qca->rx_buffer);
 	qca->buffer_size = 0;
 	dev_kfree_skb(qca->rx_skb);
--
2.34.1
Re: [PATCH 1/4 net] qca_spi: Fix SPI thread creation
Posted by Paolo Abeni 2 years ago 
On Tue, 2023-11-21 at 17:30 +0100, Stefan Wahren wrote:
> The qca_spi driver create/stop the SPI kernel thread in case
> of netdev_open/close. This is a big issue because it allows
> userspace to prevent from restarting the SPI thread after
> ring parameter changes (e.g. signals which stop the thread).
> This could be done by terminating a script which changes
> the ring parameter in a loop.
> 
> So fix this by moving create/stop of the SPI kernel into
> the init/uninit ops. The open/close ops could be realized just
> by 'park/unpark' the SPI kernel thread.
> 
> Fixes: 291ab06ecf67 ("net: qualcomm: new Ethernet over SPI driver for QCA7000")
> Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
> ---
>  drivers/net/ethernet/qualcomm/qca_spi.c | 35 ++++++++++++++++---------
>  1 file changed, 23 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/qualcomm/qca_spi.c b/drivers/net/ethernet/qualcomm/qca_spi.c
> index bec723028e96..b11a998b2456 100644
> --- a/drivers/net/ethernet/qualcomm/qca_spi.c
> +++ b/drivers/net/ethernet/qualcomm/qca_spi.c
> @@ -580,6 +580,11 @@ qcaspi_spi_thread(void *data)
>  	netdev_info(qca->net_dev, "SPI thread created\n");
>  	while (!kthread_should_stop()) {
>  		set_current_state(TASK_INTERRUPTIBLE);
> +		if (kthread_should_park()) {
> +			kthread_parkme();
> +			continue;
> +		}
> +
>  		if ((qca->intr_req == qca->intr_svc) &&
>  		    !qca->txr.skb[qca->txr.head])
>  			schedule();
> @@ -679,25 +684,17 @@ qcaspi_netdev_open(struct net_device *dev)
>  	qca->sync = QCASPI_SYNC_UNKNOWN;
>  	qcafrm_fsm_init_spi(&qca->frm_handle);
> 
> -	qca->spi_thread = kthread_run((void *)qcaspi_spi_thread,
> -				      qca, "%s", dev->name);
> -
> -	if (IS_ERR(qca->spi_thread)) {
> -		netdev_err(dev, "%s: unable to start kernel thread.\n",
> -			   QCASPI_DRV_NAME);
> -		return PTR_ERR(qca->spi_thread);
> -	}
> -
>  	ret = request_irq(qca->spi_dev->irq, qcaspi_intr_handler, 0,
>  			  dev->name, qca);
>  	if (ret) {
>  		netdev_err(dev, "%s: unable to get IRQ %d (irqval=%d).\n",
>  			   QCASPI_DRV_NAME, qca->spi_dev->irq, ret);
> -		kthread_stop(qca->spi_thread);
>  		return ret;
>  	}
> 
>  	/* SPI thread takes care of TX queue */
> +	kthread_unpark(qca->spi_thread);
> +	wake_up_process(qca->spi_thread);

The above looks racy: after 'request_irq()' the interrupt handler can
raise an irq before the thread being unparked.

Additionally I think you can drop the 'if (qca->spi_thread)' in
qcaspi_intr_handler()

Cheers,

Paolo
Re: [PATCH 1/4 net] qca_spi: Fix SPI thread creation
Posted by Stefan Wahren 2 years ago 
Hi Paolo,

Am 23.11.23 um 12:26 schrieb Paolo Abeni:
> On Tue, 2023-11-21 at 17:30 +0100, Stefan Wahren wrote:
>> The qca_spi driver create/stop the SPI kernel thread in case
>> of netdev_open/close. This is a big issue because it allows
>> userspace to prevent from restarting the SPI thread after
>> ring parameter changes (e.g. signals which stop the thread).
>> This could be done by terminating a script which changes
>> the ring parameter in a loop.
>>
>> So fix this by moving create/stop of the SPI kernel into
>> the init/uninit ops. The open/close ops could be realized just
>> by 'park/unpark' the SPI kernel thread.
>>
>> Fixes: 291ab06ecf67 ("net: qualcomm: new Ethernet over SPI driver for QCA7000")
>> Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
>> ---
>>   drivers/net/ethernet/qualcomm/qca_spi.c | 35 ++++++++++++++++---------
>>   1 file changed, 23 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/qualcomm/qca_spi.c b/drivers/net/ethernet/qualcomm/qca_spi.c
>> index bec723028e96..b11a998b2456 100644
>> --- a/drivers/net/ethernet/qualcomm/qca_spi.c
>> +++ b/drivers/net/ethernet/qualcomm/qca_spi.c
>> @@ -580,6 +580,11 @@ qcaspi_spi_thread(void *data)
>>   	netdev_info(qca->net_dev, "SPI thread created\n");
>>   	while (!kthread_should_stop()) {
>>   		set_current_state(TASK_INTERRUPTIBLE);
>> +		if (kthread_should_park()) {
>> +			kthread_parkme();
>> +			continue;
>> +		}
>> +
>>   		if ((qca->intr_req == qca->intr_svc) &&
>>   		    !qca->txr.skb[qca->txr.head])
>>   			schedule();
>> @@ -679,25 +684,17 @@ qcaspi_netdev_open(struct net_device *dev)
>>   	qca->sync = QCASPI_SYNC_UNKNOWN;
>>   	qcafrm_fsm_init_spi(&qca->frm_handle);
>>
>> -	qca->spi_thread = kthread_run((void *)qcaspi_spi_thread,
>> -				      qca, "%s", dev->name);
>> -
>> -	if (IS_ERR(qca->spi_thread)) {
>> -		netdev_err(dev, "%s: unable to start kernel thread.\n",
>> -			   QCASPI_DRV_NAME);
>> -		return PTR_ERR(qca->spi_thread);
>> -	}
>> -
>>   	ret = request_irq(qca->spi_dev->irq, qcaspi_intr_handler, 0,
>>   			  dev->name, qca);
>>   	if (ret) {
>>   		netdev_err(dev, "%s: unable to get IRQ %d (irqval=%d).\n",
>>   			   QCASPI_DRV_NAME, qca->spi_dev->irq, ret);
>> -		kthread_stop(qca->spi_thread);
>>   		return ret;
>>   	}
>>
>>   	/* SPI thread takes care of TX queue */
>> +	kthread_unpark(qca->spi_thread);
>> +	wake_up_process(qca->spi_thread);
> The above looks racy: after 'request_irq()' the interrupt handler can
> raise an irq before the thread being unparked.
yes fixing the whole resource allocation issue requires patch 1 and 2
applied, which should avoid the race. But i didn't want to combine both
patches to keep it applicable for stable. My thought was that 2 smaller
patches are more acceptable than a big one.

Should i squash them?

My concern is about the amount of affected devices. The QCA7000 is used
mostly in EV charging stations and EVs. I don't how many of them use
this driver.

> Additionally I think you can drop the 'if (qca->spi_thread)' in
> qcaspi_intr_handler()
Thanks i will check that for the next version.
>
> Cheers,
>
> Paolo
>

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