linux-kernel - Re: [PATCH v2] PCI/LINK: bw_notification: Do not leave interrupt handler NULL

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Date:   Mon, 25 Mar 2019 17:26:23 -0500
From:   "Alex G." <mr.nuke.me@...il.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     austin_bolen@...l.com, alex_gagniuc@...lteam.com,
        keith.busch@...el.com, Shyam_Iyer@...l.com, lukas@...ner.de,
        okaya@...nel.org, torvalds@...ux-foundation.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] PCI/LINK: bw_notification: Do not leave interrupt
 handler NULL

On 3/25/19 5:25 PM, Bjorn Helgaas wrote:
> On Fri, Mar 22, 2019 at 07:36:51PM -0500, Alexandru Gagniuc wrote:
>> A threaded IRQ with a NULL handler does not work with level-triggered
>> interrupts. request_threaded_irq() will return an error:
>>
>>    genirq: Threaded irq requested with handler=NULL and !ONESHOT for irq 16
>>    pcie_bw_notification: probe of 0000:00:1b.0:pcie010 failed with error -22
>>
>> For level interrupts we need to silence the interrupt before exiting
>> the IRQ handler, so just clear the PCI_EXP_LNKSTA_LBMS bit there.
>>
>> Fixes: e8303bb7a75c ("PCI/LINK: Report degraded links via link bandwidth notification")
>> Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
>> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@...il.com>
> 
> Applied with the following subject line to for-linus for v5.1, thanks!
> 
>    PCI/LINK: Supply IRQ handler so level-triggered IRQs are acked

You're so much better at formulating commit messages. That sounds a lot 
smoother. Thanks!

>> ---
>> Changes since v1:
>>   - move pcie_update_link_speed() to irq to prevent duplicate read of link_status
>>   - Add Fixes: to commit message
>>   
>>   drivers/pci/pcie/bw_notification.c | 19 ++++++++++++++-----
>>   1 file changed, 14 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/bw_notification.c b/drivers/pci/pcie/bw_notification.c
>> index d2eae3b7cc0f..c48746f1cf3c 100644
>> --- a/drivers/pci/pcie/bw_notification.c
>> +++ b/drivers/pci/pcie/bw_notification.c
>> @@ -44,11 +44,10 @@ static void pcie_disable_link_bandwidth_notification(struct pci_dev *dev)
>>   	pcie_capability_write_word(dev, PCI_EXP_LNKCTL, lnk_ctl);
>>   }
>>   
>> -static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
>> +static irqreturn_t pcie_bw_notification_irq(int irq, void *context)
>>   {
>>   	struct pcie_device *srv = context;
>>   	struct pci_dev *port = srv->port;
>> -	struct pci_dev *dev;
>>   	u16 link_status, events;
>>   	int ret;
>>   
>> @@ -58,6 +57,17 @@ static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
>>   	if (ret != PCIBIOS_SUCCESSFUL || !events)
>>   		return IRQ_NONE;
>>   
>> +	pcie_capability_write_word(port, PCI_EXP_LNKSTA, events);
>> +	pcie_update_link_speed(port->subordinate, link_status);
>> +	return IRQ_WAKE_THREAD;
>> +}
>> +
>> +static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
>> +{
>> +	struct pcie_device *srv = context;
>> +	struct pci_dev *port = srv->port;
>> +	struct pci_dev *dev;
>> +
>>   	/*
>>   	 * Print status from downstream devices, not this root port or
>>   	 * downstream switch port.
>> @@ -67,8 +77,6 @@ static irqreturn_t pcie_bw_notification_handler(int irq, void *context)
>>   		__pcie_print_link_status(dev, false);
>>   	up_read(&pci_bus_sem);
>>   
>> -	pcie_update_link_speed(port->subordinate, link_status);
>> -	pcie_capability_write_word(port, PCI_EXP_LNKSTA, events);
>>   	return IRQ_HANDLED;
>>   }
>>   
>> @@ -80,7 +88,8 @@ static int pcie_bandwidth_notification_probe(struct pcie_device *srv)
>>   	if (!pcie_link_bandwidth_notification_supported(srv->port))
>>   		return -ENODEV;
>>   
>> -	ret = request_threaded_irq(srv->irq, NULL, pcie_bw_notification_handler,
>> +	ret = request_threaded_irq(srv->irq, pcie_bw_notification_irq,
>> +				   pcie_bw_notification_handler,
>>   				   IRQF_SHARED, "PCIe BW notif", srv);
>>   	if (ret)
>>   		return ret;
>> -- 
>> 2.19.2
>>