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Commit 04df3552 authored by Jan Beulich's avatar Jan Beulich Committed by Konrad Rzeszutek Wilk
Browse files

xen/pciback: use mutex rather than spinlock in passthrough backend 



To accommodate the call to the callback function from
__xen_pcibk_publish_pci_roots(), which so far dropped and the re-
acquired the lock without checking that the list didn't actually
change, convert the code to use a mutex instead (observing that the
code taking the lock won't ever get called from non-sleepable
context).

As a result, drop the bogus use of list_for_each_entry_safe() and
remove the inappropriate dropping of the lock.

Signed-off-by: default avatarJan Beulich <jbeulich@suse.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 5fa99911

drivers/xen/xen-pciback/passthrough.c

+13 −19
Original line number Diff line number Diff line
@@ -7,13 +7,13 @@ 


#include <linux/list.h>

#include <linux/pci.h>

#include <linux/spinlock.h>

#include <linux/mutex.h>

#include "pciback.h"



struct passthrough_dev_data {

	/* Access to dev_list must be protected by lock */

	struct list_head dev_list;

	spinlock_t lock;

	struct mutex lock;

};



static struct pci_dev *__xen_pcibk_get_pci_dev(struct xen_pcibk_device *pdev,
@@ -24,9 +24,8 @@ static struct pci_dev *__xen_pcibk_get_pci_dev(struct xen_pcibk_device *pdev, 
	struct passthrough_dev_data *dev_data = pdev->pci_dev_data;

	struct pci_dev_entry *dev_entry;

	struct pci_dev *dev = NULL;

	unsigned long flags;



	spin_lock_irqsave(&dev_data->lock, flags);

	mutex_lock(&dev_data->lock);



	list_for_each_entry(dev_entry, &dev_data->dev_list, list) {

		if (domain == (unsigned int)pci_domain_nr(dev_entry->dev->bus)
@@ -37,7 +36,7 @@ static struct pci_dev *__xen_pcibk_get_pci_dev(struct xen_pcibk_device *pdev, 
		}

	}



	spin_unlock_irqrestore(&dev_data->lock, flags);

	mutex_unlock(&dev_data->lock);



	return dev;

}
@@ -48,7 +47,6 @@ static int __xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev, 
{

	struct passthrough_dev_data *dev_data = pdev->pci_dev_data;

	struct pci_dev_entry *dev_entry;

	unsigned long flags;

	unsigned int domain, bus, devfn;

	int err;
@@ -57,9 +55,9 @@ static int __xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev, 
		return -ENOMEM;

	dev_entry->dev = dev;



	spin_lock_irqsave(&dev_data->lock, flags);

	mutex_lock(&dev_data->lock);

	list_add_tail(&dev_entry->list, &dev_data->dev_list);

	spin_unlock_irqrestore(&dev_data->lock, flags);

	mutex_unlock(&dev_data->lock);



	/* Publish this device. */

	domain = (unsigned int)pci_domain_nr(dev->bus);
@@ -76,9 +74,8 @@ static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev, 
	struct passthrough_dev_data *dev_data = pdev->pci_dev_data;

	struct pci_dev_entry *dev_entry, *t;

	struct pci_dev *found_dev = NULL;

	unsigned long flags;



	spin_lock_irqsave(&dev_data->lock, flags);

	mutex_lock(&dev_data->lock);



	list_for_each_entry_safe(dev_entry, t, &dev_data->dev_list, list) {

		if (dev_entry->dev == dev) {
@@ -88,7 +85,7 @@ static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev, 
		}

	}



	spin_unlock_irqrestore(&dev_data->lock, flags);

	mutex_unlock(&dev_data->lock);



	if (found_dev)

		pcistub_put_pci_dev(found_dev);
@@ -102,7 +99,7 @@ static int __xen_pcibk_init_devices(struct xen_pcibk_device *pdev) 
	if (!dev_data)

		return -ENOMEM;



	spin_lock_init(&dev_data->lock);

	mutex_init(&dev_data->lock);



	INIT_LIST_HEAD(&dev_data->dev_list);
@@ -116,14 +113,14 @@ static int __xen_pcibk_publish_pci_roots(struct xen_pcibk_device *pdev, 
{

	int err = 0;

	struct passthrough_dev_data *dev_data = pdev->pci_dev_data;

	struct pci_dev_entry *dev_entry, *e, *tmp;

	struct pci_dev_entry *dev_entry, *e;

	struct pci_dev *dev;

	int found;

	unsigned int domain, bus;



	spin_lock(&dev_data->lock);

	mutex_lock(&dev_data->lock);



	list_for_each_entry_safe(dev_entry, tmp, &dev_data->dev_list, list) {

	list_for_each_entry(dev_entry, &dev_data->dev_list, list) {

		/* Only publish this device as a root if none of its

		 * parent bridges are exported

		 */
@@ -142,16 +139,13 @@ static int __xen_pcibk_publish_pci_roots(struct xen_pcibk_device *pdev, 
		bus = (unsigned int)dev_entry->dev->bus->number;



		if (!found) {

			spin_unlock(&dev_data->lock);

			err = publish_root_cb(pdev, domain, bus);

			if (err)

				break;

			spin_lock(&dev_data->lock);

		}

	}



	if (!err)

		spin_unlock(&dev_data->lock);

	mutex_unlock(&dev_data->lock);



	return err;

}