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: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 13 insertions, 19 deletions

diff --git a/drivers/xen/xen-pciback/passthrough.c b/drivers/xen/xen-pciback/passthrough.c
index 1d32a9a42c01..e01e4b6ef267 100644
--- a/drivers/xen/xen-pciback/passthrough.c
+++ b/drivers/xen/xen-pciback/passthrough.c
@@ -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;
 }