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authorKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2014-12-04 00:40:26 +0300
committerDavid Vrabel <david.vrabel@citrix.com>2014-12-04 15:41:58 +0300
commite8801a7418dda995a70f30874aef77e6d064828e (patch)
treeee4e691009b468c5397216b9e5776c6c239cc51e /drivers/xen
parent2c3fc8d26dd09b9d7069687eead849ee81c78e46 (diff)
downloadlinux-e8801a7418dda995a70f30874aef77e6d064828e.tar.xz
xen/pciback: Don't deadlock when unbinding.
As commit 0a9fd0152929db372ff61b0d6c280fdd34ae8bdb 'xen/pciback: Document the entry points for 'pcistub_put_pci_dev'' explained there are four entry points in this function. Two of them are when the user fiddles in the SysFS to unbind a device which might be in use by a guest or not. Both 'unbind' states will cause a deadlock as the the PCI lock has already been taken, which then pci_device_reset tries to take. We can simplify this by requiring that all callers of pcistub_put_pci_dev MUST hold the device lock. And then we can just call the lockless version of pci_device_reset. To make it even simpler we will modify xen_pcibk_release_pci_dev to quality whether it should take a lock or not - as it ends up calling xen_pcibk_release_pci_dev and needs to hold the lock. Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Diffstat (limited to 'drivers/xen')
-rw-r--r--drivers/xen/xen-pciback/passthrough.c14
-rw-r--r--drivers/xen/xen-pciback/pci_stub.c12
-rw-r--r--drivers/xen/xen-pciback/pciback.h7
-rw-r--r--drivers/xen/xen-pciback/vpci.c14
-rw-r--r--drivers/xen/xen-pciback/xenbus.c2
5 files changed, 33 insertions, 16 deletions
diff --git a/drivers/xen/xen-pciback/passthrough.c b/drivers/xen/xen-pciback/passthrough.c
index 828dddc360df..f16a30e2a110 100644
--- a/drivers/xen/xen-pciback/passthrough.c
+++ b/drivers/xen/xen-pciback/passthrough.c
@@ -69,7 +69,7 @@ static int __xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev,
}
static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
- struct pci_dev *dev)
+ struct pci_dev *dev, bool lock)
{
struct passthrough_dev_data *dev_data = pdev->pci_dev_data;
struct pci_dev_entry *dev_entry, *t;
@@ -87,8 +87,13 @@ static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
mutex_unlock(&dev_data->lock);
- if (found_dev)
+ if (found_dev) {
+ if (lock)
+ device_lock(&found_dev->dev);
pcistub_put_pci_dev(found_dev);
+ if (lock)
+ device_unlock(&found_dev->dev);
+ }
}
static int __xen_pcibk_init_devices(struct xen_pcibk_device *pdev)
@@ -156,8 +161,11 @@ static void __xen_pcibk_release_devices(struct xen_pcibk_device *pdev)
struct pci_dev_entry *dev_entry, *t;
list_for_each_entry_safe(dev_entry, t, &dev_data->dev_list, list) {
+ struct pci_dev *dev = dev_entry->dev;
list_del(&dev_entry->list);
- pcistub_put_pci_dev(dev_entry->dev);
+ device_lock(&dev->dev);
+ pcistub_put_pci_dev(dev);
+ device_unlock(&dev->dev);
kfree(dev_entry);
}
diff --git a/drivers/xen/xen-pciback/pci_stub.c b/drivers/xen/xen-pciback/pci_stub.c
index 017069a455d4..9cbe1a31c1e5 100644
--- a/drivers/xen/xen-pciback/pci_stub.c
+++ b/drivers/xen/xen-pciback/pci_stub.c
@@ -250,6 +250,8 @@ struct pci_dev *pcistub_get_pci_dev(struct xen_pcibk_device *pdev,
* - 'echo BDF > unbind' with a guest still using it. See pcistub_remove
*
* As such we have to be careful.
+ *
+ * To make this easier, the caller has to hold the device lock.
*/
void pcistub_put_pci_dev(struct pci_dev *dev)
{
@@ -276,11 +278,8 @@ void pcistub_put_pci_dev(struct pci_dev *dev)
/* Cleanup our device
* (so it's ready for the next domain)
*/
-
- /* This is OK - we are running from workqueue context
- * and want to inhibit the user from fiddling with 'reset'
- */
- pci_reset_function(dev);
+ lockdep_assert_held(&dev->dev.mutex);
+ __pci_reset_function_locked(dev);
pci_restore_state(dev);
/* This disables the device. */
@@ -567,7 +566,8 @@ static void pcistub_remove(struct pci_dev *dev)
/* N.B. This ends up calling pcistub_put_pci_dev which ends up
* doing the FLR. */
xen_pcibk_release_pci_dev(found_psdev->pdev,
- found_psdev->dev);
+ found_psdev->dev,
+ false /* caller holds the lock. */);
}
spin_lock_irqsave(&pcistub_devices_lock, flags);
diff --git a/drivers/xen/xen-pciback/pciback.h b/drivers/xen/xen-pciback/pciback.h
index f72af87640e0..58e38d586f52 100644
--- a/drivers/xen/xen-pciback/pciback.h
+++ b/drivers/xen/xen-pciback/pciback.h
@@ -99,7 +99,8 @@ struct xen_pcibk_backend {
unsigned int *domain, unsigned int *bus,
unsigned int *devfn);
int (*publish)(struct xen_pcibk_device *pdev, publish_pci_root_cb cb);
- void (*release)(struct xen_pcibk_device *pdev, struct pci_dev *dev);
+ void (*release)(struct xen_pcibk_device *pdev, struct pci_dev *dev,
+ bool lock);
int (*add)(struct xen_pcibk_device *pdev, struct pci_dev *dev,
int devid, publish_pci_dev_cb publish_cb);
struct pci_dev *(*get)(struct xen_pcibk_device *pdev,
@@ -122,10 +123,10 @@ static inline int xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev,
}
static inline void xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
- struct pci_dev *dev)
+ struct pci_dev *dev, bool lock)
{
if (xen_pcibk_backend && xen_pcibk_backend->release)
- return xen_pcibk_backend->release(pdev, dev);
+ return xen_pcibk_backend->release(pdev, dev, lock);
}
static inline struct pci_dev *
diff --git a/drivers/xen/xen-pciback/vpci.c b/drivers/xen/xen-pciback/vpci.c
index 51afff96c515..c99f8bb1c56c 100644
--- a/drivers/xen/xen-pciback/vpci.c
+++ b/drivers/xen/xen-pciback/vpci.c
@@ -145,7 +145,7 @@ out:
}
static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
- struct pci_dev *dev)
+ struct pci_dev *dev, bool lock)
{
int slot;
struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
@@ -169,8 +169,13 @@ static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
out:
mutex_unlock(&vpci_dev->lock);
- if (found_dev)
+ if (found_dev) {
+ if (lock)
+ device_lock(&found_dev->dev);
pcistub_put_pci_dev(found_dev);
+ if (lock)
+ device_unlock(&found_dev->dev);
+ }
}
static int __xen_pcibk_init_devices(struct xen_pcibk_device *pdev)
@@ -208,8 +213,11 @@ static void __xen_pcibk_release_devices(struct xen_pcibk_device *pdev)
struct pci_dev_entry *e, *tmp;
list_for_each_entry_safe(e, tmp, &vpci_dev->dev_list[slot],
list) {
+ struct pci_dev *dev = e->dev;
list_del(&e->list);
- pcistub_put_pci_dev(e->dev);
+ device_lock(&dev->dev);
+ pcistub_put_pci_dev(dev);
+ device_unlock(&dev->dev);
kfree(e);
}
}
diff --git a/drivers/xen/xen-pciback/xenbus.c b/drivers/xen/xen-pciback/xenbus.c
index ad8d30c088fe..eeee499d4b3c 100644
--- a/drivers/xen/xen-pciback/xenbus.c
+++ b/drivers/xen/xen-pciback/xenbus.c
@@ -291,7 +291,7 @@ static int xen_pcibk_remove_device(struct xen_pcibk_device *pdev,
/* N.B. This ends up calling pcistub_put_pci_dev which ends up
* doing the FLR. */
- xen_pcibk_release_pci_dev(pdev, dev);
+ xen_pcibk_release_pci_dev(pdev, dev, true /* use the lock. */);
out:
return err;