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

From: Long Li <longli@microsoft.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@microsoft.com>
---
 drivers/pci/controller/pci-hyperv.c | 34 +++--------------------------
 1 file changed, 3 insertions(+), 31 deletions(-)

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

From: longli@linuxonhyperv.com <redacted> Sent: Wednesday, May 12, 2021 1:07 AM

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@microsoft.com>
---
 drivers/pci/controller/pci-hyperv.c | 34 +++--------------------------
 1 file changed, 3 insertions(+), 31 deletions(-)

Reviewed-by: Michael Kelley <redacted>

On Wed, May 12, 2021 at 01:06:49AM -0700, longli@linuxonhyperv.com wrote:

From: Long Li <longli@microsoft.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@microsoft.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

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@linuxonhyperv.com
wrote:

quoted

From: Long Li <longli@microsoft.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@microsoft.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).

Will do next time.  Thank you!

Long

Thanks,
Lorenzo

quoted

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)

quoted

 	}
 	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)

quoted

 		break;
 	}

-	put_hvpcibus(hbus);
 	kfree(dr);
 }

@@ -2194,12 +2186,10 @@ static int hv_pci_start_relations_work(struct

hv_pcibus_device *hbus,

quoted

 	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)

quoted

 	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)

quoted

 	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)

quoted

 	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