Re: [PATCH V4 1/3] driver core: mark device as irq affinity managed if any irq is managed

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Jul 15, 2021 at 08:08:42PM +0800, Ming Lei wrote:
> irq vector allocation with managed affinity may be used by driver, and
> blk-mq needs this info because managed irq will be shutdown when all
> CPUs in the affinity mask are offline.
> 
> The info of using managed irq is often produced by drivers(pci subsystem,

Add space between "drivers" and "(".
s/pci/PCI/

Does this "managed IRQ" (or "managed affinity", not sure what the
correct terminology is here) have something to do with devm?

> platform device, ...), and it is consumed by blk-mq, so different subsystems
> are involved in this info flow

Add period at end of sentence.

> Address this issue by adding one field of .irq_affinity_managed into
> 'struct device'.
> 
> Suggested-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/base/platform.c | 7 +++++++
>  drivers/pci/msi.c       | 3 +++
>  include/linux/device.h  | 1 +
>  3 files changed, 11 insertions(+)
> 
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 8640578f45e9..d28cb91d5cf9 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -388,6 +388,13 @@ int devm_platform_get_irqs_affinity(struct platform_device *dev,
>  				ptr->irq[i], ret);
>  			goto err_free_desc;
>  		}
> +
> +		/*
> +		 * mark the device as irq affinity managed if any irq affinity
> +		 * descriptor is managed
> +		 */
> +		if (desc[i].is_managed)
> +			dev->dev.irq_affinity_managed = true;
>  	}
>  
>  	devres_add(&dev->dev, ptr);
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 3d6db20d1b2b..7ddec90b711d 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -1197,6 +1197,7 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
>  	if (flags & PCI_IRQ_AFFINITY) {
>  		if (!affd)
>  			affd = &msi_default_affd;
> +		dev->dev.irq_affinity_managed = true;

This is really opaque to me.  I can't tell what the connection between
PCI_IRQ_AFFINITY and irq_affinity_managed is.

AFAICT the only place irq_affinity_managed is ultimately used is
blk_mq_hctx_notify_offline(), and there's no obvious connection
between that and this code.

>  	} else {
>  		if (WARN_ON(affd))
>  			affd = NULL;
> @@ -1215,6 +1216,8 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
>  			return nvecs;
>  	}
>  
> +	dev->dev.irq_affinity_managed = false;
> +
>  	/* use legacy IRQ if allowed */
>  	if (flags & PCI_IRQ_LEGACY) {
>  		if (min_vecs == 1 && dev->irq) {
> diff --git a/include/linux/device.h b/include/linux/device.h
> index 59940f1744c1..9ec6e671279e 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -569,6 +569,7 @@ struct device {
>  #ifdef CONFIG_DMA_OPS_BYPASS
>  	bool			dma_ops_bypass : 1;
>  #endif
> +	bool			irq_affinity_managed : 1;
>  };
>  
>  /**
> -- 
> 2.31.1
> 
> 
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