[libvirt] [PATCH] nwfilter: fix deadlock caused updating network device and nwfilter

[Pavel Hrdina]

Commit 6e5c79a1 tried to fix deadlock between nwfilter{Define,Undefine}
and starting of guest, but this same deadlock is also for
updating/attaching network device to domain.

The deadlock was introduced by removing global QEMU driver lock because
nwfilter was counting on this lock and ensure that all driver locks are
locked inside of nwfilter{Define,Undefine}.

This patch extends usage of virNWFilterReadLockFilterUpdates to prevent
the deadlock for all possible paths in QEMU driver. LXC and UML drivers
still have global lock.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1143780

Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
---

This is temporary fix for the deadlock issue as I'm planning to create global
libvirt jobs (similar to QEMU domain jobs) and use it for other drivers and
for example for nwfilters too.

 src/qemu/qemu_driver.c    | 12 ++++++++++++
 src/qemu/qemu_migration.c |  3 +++
 src/qemu/qemu_process.c   |  4 ++++
 3 files changed, 19 insertions(+)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 6acaea8..9e6f505 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -5937,6 +5937,8 @@ qemuDomainRestoreFlags(virConnectPtr conn,
         def = tmp;
     }
 
+    virNWFilterReadLockFilterUpdates();
+
     if (!(vm = virDomainObjListAdd(driver->domains, def,
                                    driver->xmlopt,
                                    VIR_DOMAIN_OBJ_LIST_ADD_LIVE |
@@ -5978,6 +5980,7 @@ qemuDomainRestoreFlags(virConnectPtr conn,
     virFileWrapperFdFree(wrapperFd);
     if (vm)
         virObjectUnlock(vm);
+    virNWFilterUnlockFilterUpdates();
     return ret;
 }
 
@@ -7502,6 +7505,8 @@ static int qemuDomainAttachDeviceFlags(virDomainPtr dom, const char *xml,
 
     affect = flags & (VIR_DOMAIN_AFFECT_LIVE | VIR_DOMAIN_AFFECT_CONFIG);
 
+    virNWFilterReadLockFilterUpdates();
+
     if (!(caps = virQEMUDriverGetCapabilities(driver, false)))
         goto cleanup;
 
@@ -7614,6 +7619,7 @@ static int qemuDomainAttachDeviceFlags(virDomainPtr dom, const char *xml,
         virObjectUnlock(vm);
     virObjectUnref(caps);
     virObjectUnref(cfg);
+    virNWFilterUnlockFilterUpdates();
     return ret;
 }
 
@@ -7644,6 +7650,8 @@ static int qemuDomainUpdateDeviceFlags(virDomainPtr dom,
                   VIR_DOMAIN_AFFECT_CONFIG |
                   VIR_DOMAIN_DEVICE_MODIFY_FORCE, -1);
 
+    virNWFilterReadLockFilterUpdates();
+
     cfg = virQEMUDriverGetConfig(driver);
 
     affect = flags & (VIR_DOMAIN_AFFECT_LIVE | VIR_DOMAIN_AFFECT_CONFIG);
@@ -7760,6 +7768,7 @@ static int qemuDomainUpdateDeviceFlags(virDomainPtr dom,
         virObjectUnlock(vm);
     virObjectUnref(caps);
     virObjectUnref(cfg);
+    virNWFilterUnlockFilterUpdates();
     return ret;
 }
 
@@ -14510,6 +14519,8 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
      * and use of FORCE can cause multiple transitions.
      */
 
+    virNWFilterReadLockFilterUpdates();
+
     if (!(vm = qemuDomObjFromSnapshot(snapshot)))
         return -1;
 
@@ -14831,6 +14842,7 @@ qemuDomainRevertToSnapshot(virDomainSnapshotPtr snapshot,
         virObjectUnlock(vm);
     virObjectUnref(caps);
     virObjectUnref(cfg);
+    virNWFilterUnlockFilterUpdates();
 
     return ret;
 }
diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 94a4cf6..18242ae 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -2666,6 +2666,8 @@ qemuMigrationPrepareAny(virQEMUDriverPtr driver,
             goto cleanup;
     }
 
+    virNWFilterReadLockFilterUpdates();
+
     if (!(vm = virDomainObjListAdd(driver->domains, *def,
                                    driver->xmlopt,
                                    VIR_DOMAIN_OBJ_LIST_ADD_LIVE |
@@ -2825,6 +2827,7 @@ qemuMigrationPrepareAny(virQEMUDriverPtr driver,
         qemuDomainEventQueue(driver, event);
     qemuMigrationCookieFree(mig);
     virObjectUnref(caps);
+    virNWFilterUnlockFilterUpdates();
     return ret;
 
  stop:
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 26d4948..409a672 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -3422,6 +3422,8 @@ qemuProcessReconnect(void *opaque)
 
     VIR_FREE(data);
 
+    virNWFilterReadLockFilterUpdates();
+
     virObjectLock(obj);
 
     cfg = virQEMUDriverGetConfig(driver);
@@ -3573,6 +3575,7 @@ qemuProcessReconnect(void *opaque)
 
     virObjectUnref(conn);
     virObjectUnref(cfg);
+    virNWFilterUnlockFilterUpdates();
 
     return;
 
@@ -3608,6 +3611,7 @@ qemuProcessReconnect(void *opaque)
     }
     virObjectUnref(conn);
     virObjectUnref(cfg);
+    virNWFilterUnlockFilterUpdates();
 }
 
 static int
-- 
2.0.4