Jan Beulich
2011-Sep-19 16:32 UTC
[Xen-devel] [PATCH] 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>
---
drivers/xen/xen-pciback/passthrough.c | 32 +++++++++++++-------------------
1 file changed, 13 insertions(+), 19 deletions(-)
--- 3.1-rc6/drivers/xen/xen-pciback/passthrough.c
+++ 3.1-rc6-xen-pciback-passthr-mutex/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_p
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_p
}
}
- 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(struc
{
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(struc
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 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(
}
}
- 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(stru
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
{
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
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;
}
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