linux-kernel - Re: [Patch v3 2/2] PCI: hv: Remove unused refcount and supporting functions for handling bus device removal

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Date:   Thu, 3 Jun 2021 18:27:22 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     longli@...uxonhyperv.com
Cc:     "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        linux-hyperv@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, Long Li <longli@...rosoft.com>
Subject: Re: [Patch v3 2/2] PCI: hv: Remove unused refcount and supporting
 functions for handling bus device removal

On Wed, May 12, 2021 at 01:06:49AM -0700, longli@...uxonhyperv.com wrote:
> From: Long Li <longli@...rosoft.com>
> 
> With the new method of flushing/stopping the workqueue before doing bus
> removal, the old mechanism of using refcount and wait for completion
> is no longer needed. Remove those dead code.
> 
> Signed-off-by: Long Li <longli@...rosoft.com>
> ---
>  drivers/pci/controller/pci-hyperv.c | 34 +++--------------------------
>  1 file changed, 3 insertions(+), 31 deletions(-)

I'd be grateful if in the future you can send threaded patch series so
that tools like b4 can detect the thread and create the mbox
accordingly.

No need to resend this one (maybe I need to trim patch(2) Subject).

Thanks,
Lorenzo

> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index c6122a1b0c46..9499ae3275fe 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -452,7 +452,6 @@ struct hv_pcibus_device {
>  	/* Protocol version negotiated with the host */
>  	enum pci_protocol_version_t protocol_version;
>  	enum hv_pcibus_state state;
> -	refcount_t remove_lock;
>  	struct hv_device *hdev;
>  	resource_size_t low_mmio_space;
>  	resource_size_t high_mmio_space;
> @@ -460,7 +459,6 @@ struct hv_pcibus_device {
>  	struct resource *low_mmio_res;
>  	struct resource *high_mmio_res;
>  	struct completion *survey_event;
> -	struct completion remove_event;
>  	struct pci_bus *pci_bus;
>  	spinlock_t config_lock;	/* Avoid two threads writing index page */
>  	spinlock_t device_list_lock;	/* Protect lists below */
> @@ -593,9 +591,6 @@ static void put_pcichild(struct hv_pci_dev *hpdev)
>  		kfree(hpdev);
>  }
>  
> -static void get_hvpcibus(struct hv_pcibus_device *hv_pcibus);
> -static void put_hvpcibus(struct hv_pcibus_device *hv_pcibus);
> -
>  /*
>   * There is no good way to get notified from vmbus_onoffer_rescind(),
>   * so let's use polling here, since this is not a hot path.
> @@ -2067,10 +2062,8 @@ static void pci_devices_present_work(struct work_struct *work)
>  	}
>  	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
>  
> -	if (!dr) {
> -		put_hvpcibus(hbus);
> +	if (!dr)
>  		return;
> -	}
>  
>  	/* First, mark all existing children as reported missing. */
>  	spin_lock_irqsave(&hbus->device_list_lock, flags);
> @@ -2153,7 +2146,6 @@ static void pci_devices_present_work(struct work_struct *work)
>  		break;
>  	}
>  
> -	put_hvpcibus(hbus);
>  	kfree(dr);
>  }
>  
> @@ -2194,12 +2186,10 @@ static int hv_pci_start_relations_work(struct hv_pcibus_device *hbus,
>  	list_add_tail(&dr->list_entry, &hbus->dr_list);
>  	spin_unlock_irqrestore(&hbus->device_list_lock, flags);
>  
> -	if (pending_dr) {
> +	if (pending_dr)
>  		kfree(dr_wrk);
> -	} else {
> -		get_hvpcibus(hbus);
> +	else
>  		queue_work(hbus->wq, &dr_wrk->wrk);
> -	}
>  
>  	return 0;
>  }
> @@ -2342,8 +2332,6 @@ static void hv_eject_device_work(struct work_struct *work)
>  	put_pcichild(hpdev);
>  	put_pcichild(hpdev);
>  	/* hpdev has been freed. Do not use it any more. */
> -
> -	put_hvpcibus(hbus);
>  }
>  
>  /**
> @@ -2367,7 +2355,6 @@ static void hv_pci_eject_device(struct hv_pci_dev *hpdev)
>  	hpdev->state = hv_pcichild_ejecting;
>  	get_pcichild(hpdev);
>  	INIT_WORK(&hpdev->wrk, hv_eject_device_work);
> -	get_hvpcibus(hbus);
>  	queue_work(hbus->wq, &hpdev->wrk);
>  }
>  
> @@ -2967,17 +2954,6 @@ static int hv_send_resources_released(struct hv_device *hdev)
>  	return 0;
>  }
>  
> -static void get_hvpcibus(struct hv_pcibus_device *hbus)
> -{
> -	refcount_inc(&hbus->remove_lock);
> -}
> -
> -static void put_hvpcibus(struct hv_pcibus_device *hbus)
> -{
> -	if (refcount_dec_and_test(&hbus->remove_lock))
> -		complete(&hbus->remove_event);
> -}
> -
>  #define HVPCI_DOM_MAP_SIZE (64 * 1024)
>  static DECLARE_BITMAP(hvpci_dom_map, HVPCI_DOM_MAP_SIZE);
>  
> @@ -3097,14 +3073,12 @@ static int hv_pci_probe(struct hv_device *hdev,
>  	hbus->sysdata.domain = dom;
>  
>  	hbus->hdev = hdev;
> -	refcount_set(&hbus->remove_lock, 1);
>  	INIT_LIST_HEAD(&hbus->children);
>  	INIT_LIST_HEAD(&hbus->dr_list);
>  	INIT_LIST_HEAD(&hbus->resources_for_children);
>  	spin_lock_init(&hbus->config_lock);
>  	spin_lock_init(&hbus->device_list_lock);
>  	spin_lock_init(&hbus->retarget_msi_interrupt_lock);
> -	init_completion(&hbus->remove_event);
>  	hbus->wq = alloc_ordered_workqueue("hv_pci_%x", 0,
>  					   hbus->sysdata.domain);
>  	if (!hbus->wq) {
> @@ -3341,8 +3315,6 @@ static int hv_pci_remove(struct hv_device *hdev)
>  	hv_pci_free_bridge_windows(hbus);
>  	irq_domain_remove(hbus->irq_domain);
>  	irq_domain_free_fwnode(hbus->sysdata.fwnode);
> -	put_hvpcibus(hbus);
> -	wait_for_completion(&hbus->remove_event);
>  
>  	hv_put_dom_num(hbus->sysdata.domain);
>  
> -- 
> 2.27.0
>