Push nwfilter update locking up to top level

The NWFilter code has as a deadlock race condition between
the virNWFilter{Define,Undefine} APIs and starting of guest
VMs due to mis-matched lock ordering.

In the virNWFilter{Define,Undefine} codepaths the lock ordering
is

  1. nwfilter driver lock
  2. virt driver lock
  3. nwfilter update lock
  4. domain object lock

In the VM guest startup paths the lock ordering is

  1. virt driver lock
  2. domain object lock
  3. nwfilter update lock

As can be seen the domain object and nwfilter update locks are
not acquired in a consistent order.

The fix used is to push the nwfilter update lock upto the top
level resulting in a lock ordering for virNWFilter{Define,Undefine}
of

  1. nwfilter driver lock
  2. nwfilter update lock
  3. virt driver lock
  4. domain object lock

and VM start using

  1. nwfilter update lock
  2. virt driver lock
  3. domain object lock

This has the effect of serializing VM startup once again, even if
no nwfilters are applied to the guest. There is also the possibility
of deadlock due to a call graph loop via virNWFilterInstantiate
and virNWFilterInstantiateFilterLate.

These two problems mean the lock must be turned into a read/write
lock instead of a plain mutex at the same time. The lock is used to
serialize changes to the "driver->nwfilters" hash, so the write lock
only needs to be held by the define/undefine methods. All other
methods can rely on a read lock which allows good concurrency.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
(cherry picked from commit 6e5c79a1b5a8b3a23e7df7ffe58fb272aa17fbfb)

Conflicts:
	src/conf/nwfilter_conf.c
          - virReportOOMError() in context of one hunk.
	src/lxc/lxc_driver.c
          - functions renamed, and lxc object locking changed, creating
            a conflict in the context.

diff --git a/src/conf/nwfilter_conf.c b/src/conf/nwfilter_conf.c
index 94b4fe99da61e99cc68544cbc19c515300913358..e943babe43b9793ada3f3d1773879b5673ff50c5 100644 (file)
--- a/src/conf/nwfilter_conf.c
+++ b/src/conf/nwfilter_conf.c
@@ -2,7 +2,7 @@
  * nwfilter_conf.c: network filter XML processing
  *                  (derived from storage_conf.c)
  *
- * Copyright (C) 2006-2012 Red Hat, Inc.
+ * Copyright (C) 2006-2012, 2014 Red Hat, Inc.
  * Copyright (C) 2006-2008 Daniel P. Berrange
  *
  * Copyright (C) 2010-2011 IBM Corporation
@@ -143,17 +143,22 @@ static const struct int_map chain_priorities[] = {
 /*
  * only one filter update allowed
  */
-static virMutex updateMutex;
+static virRWLock updateLock;
 static bool initialized = false;
 
 void
-virNWFilterLockFilterUpdates(void) {
-    virMutexLock(&updateMutex);
+virNWFilterReadLockFilterUpdates(void) {
+    virRWLockRead(&updateLock);
+}
+
+void
+virNWFilterWriteLockFilterUpdates(void) {
+    virRWLockWrite(&updateLock);
 }
 
 void
 virNWFilterUnlockFilterUpdates(void) {
-    virMutexUnlock(&updateMutex);
+    virRWLockUnlock(&updateLock);
 }
 
 
@@ -2992,14 +2997,12 @@ virNWFilterObjAssignDef(virNWFilterObjListPtr nwfilters,
         return NULL;
     }
 
-    virNWFilterLockFilterUpdates();
 
     if ((nwfilter = virNWFilterObjFindByName(nwfilters, def->name))) {
 
         if (virNWFilterDefEqual(def, nwfilter->def, false)) {
             virNWFilterDefFree(nwfilter->def);
             nwfilter->def = def;
-            virNWFilterUnlockFilterUpdates();
             return nwfilter;
         }
 
@@ -3007,7 +3010,6 @@ virNWFilterObjAssignDef(virNWFilterObjListPtr nwfilters,
         /* trigger the update on VMs referencing the filter */
         if (virNWFilterTriggerVMFilterRebuild()) {
             nwfilter->newDef = NULL;
-            virNWFilterUnlockFilterUpdates();
             virNWFilterObjUnlock(nwfilter);
             return NULL;
         }
@@ -3015,12 +3017,9 @@ virNWFilterObjAssignDef(virNWFilterObjListPtr nwfilters,
         virNWFilterDefFree(nwfilter->def);
         nwfilter->def = def;
         nwfilter->newDef = NULL;
-        virNWFilterUnlockFilterUpdates();
         return nwfilter;
     }
 
-    virNWFilterUnlockFilterUpdates();
-
     if (VIR_ALLOC(nwfilter) < 0) {
         virReportOOMError();
         return NULL;
@@ -3492,7 +3491,7 @@ int virNWFilterConfLayerInit(virDomainObjListIterator domUpdateCB,
 
     initialized = true;
 
-    if (virMutexInitRecursive(&updateMutex) < 0)
+    if (virRWLockInit(&updateLock) < 0)
         return -1;
 
     return 0;
@@ -3504,7 +3503,7 @@ void virNWFilterConfLayerShutdown(void)
     if (!initialized)
         return;
 
-    virMutexDestroy(&updateMutex);
+    virRWLockDestroy(&updateLock);
 
     initialized = false;
     virNWFilterDomainFWUpdateOpaque = NULL;

diff --git a/src/conf/nwfilter_conf.h b/src/conf/nwfilter_conf.h
index 29906f1389c6920515a2a2ef7732e093943f5e02..d460a0856531c628a49560eae700298ab2d6c34a 100644 (file)
--- a/src/conf/nwfilter_conf.h
+++ b/src/conf/nwfilter_conf.h
@@ -716,7 +716,8 @@ virNWFilterDefPtr virNWFilterDefParseFile(const char *filename);
 void virNWFilterObjLock(virNWFilterObjPtr obj);
 void virNWFilterObjUnlock(virNWFilterObjPtr obj);
 
-void virNWFilterLockFilterUpdates(void);
+void virNWFilterWriteLockFilterUpdates(void);
+void virNWFilterReadLockFilterUpdates(void);
 void virNWFilterUnlockFilterUpdates(void);
 
 int virNWFilterConfLayerInit(virDomainObjListIterator domUpdateCB, void *opaque);

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index a6348bcfeb40feb996247698baf10ccd7e86c563..753c698d4b7f3bdea153ff472bf494cb71d10409 100644 (file)
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -551,7 +551,6 @@ virNWFilterDefParseString;
 virNWFilterInstFiltersOnAllVMs;
 virNWFilterJumpTargetTypeToString;
 virNWFilterLoadAllConfigs;
-virNWFilterLockFilterUpdates;
 virNWFilterObjAssignDef;
 virNWFilterObjDeleteDef;
 virNWFilterObjFindByName;
@@ -563,6 +562,7 @@ virNWFilterObjSaveDef;
 virNWFilterObjUnlock;
 virNWFilterPrintStateMatchFlags;
 virNWFilterPrintTCPFlags;
+virNWFilterReadLockFilterUpdates;
 virNWFilterRegisterCallbackDriver;
 virNWFilterRuleActionTypeToString;
 virNWFilterRuleDirectionTypeToString;
@@ -570,6 +570,7 @@ virNWFilterRuleProtocolTypeToString;
 virNWFilterTestUnassignDef;
 virNWFilterUnlockFilterUpdates;
 virNWFilterUnRegisterCallbackDriver;
+virNWFilterWriteLockFilterUpdates;
 
 
 # conf/nwfilter_ipaddrmap.h

diff --git a/src/lxc/lxc_driver.c b/src/lxc/lxc_driver.c
index fed3775a2354f707e8f11d46e18233a07ad7d606..d59f0f6a9eb49874cb5748a631061d75228a8576 100644 (file)
--- a/src/lxc/lxc_driver.c
+++ b/src/lxc/lxc_driver.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2010-2013 Red Hat, Inc.
+ * Copyright (C) 2010-2014 Red Hat, Inc.
  * Copyright IBM Corp. 2008
  *
  * lxc_driver.c: linux container driver functions
@@ -1102,6 +1102,8 @@ static int lxcDomainCreateWithFlags(virDomainPtr dom, unsigned int flags)
 
     virCheckFlags(VIR_DOMAIN_START_AUTODESTROY, -1);
 
+    virNWFilterReadLockFilterUpdates();
+
     lxcDriverLock(driver);
     vm = virDomainObjListFindByUUID(driver->domains, dom->uuid);
     if (!vm) {
@@ -1146,6 +1148,7 @@ cleanup:
     if (event)
         virDomainEventStateQueue(driver->domainEventState, event);
     lxcDriverUnlock(driver);
+    virNWFilterUnlockFilterUpdates();
     return ret;
 }
 
@@ -1184,6 +1187,8 @@ lxcDomainCreateXML(virConnectPtr conn,
 
     virCheckFlags(VIR_DOMAIN_START_AUTODESTROY, NULL);
 
+    virNWFilterReadLockFilterUpdates();
+
     lxcDriverLock(driver);
     if (!(def = virDomainDefParseString(xml, driver->caps, driver->xmlopt,
                                         1 << VIR_DOMAIN_VIRT_LXC,
@@ -1235,6 +1240,7 @@ cleanup:
     if (event)
         virDomainEventStateQueue(driver->domainEventState, event);
     lxcDriverUnlock(driver);
+    virNWFilterUnlockFilterUpdates();
     return dom;
 }
 

diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c
index 630f6227256f9b4806487e9807116591647c0354..2d5dcaf8311dae2840b557493440633fafde5e85 100644 (file)
--- a/src/nwfilter/nwfilter_driver.c
+++ b/src/nwfilter/nwfilter_driver.c
@@ -284,12 +284,14 @@ nwfilterStateReload(void)
     virNWFilterLearnThreadsTerminate(true);
 
     nwfilterDriverLock(driverState);
+    virNWFilterWriteLockFilterUpdates();
     virNWFilterCallbackDriversLock();
 
     virNWFilterLoadAllConfigs(&driverState->nwfilters,
                               driverState->configDir);
 
     virNWFilterCallbackDriversUnlock();
+    virNWFilterUnlockFilterUpdates();
     nwfilterDriverUnlock(driverState);
 
     virNWFilterInstFiltersOnAllVMs();
@@ -540,6 +542,7 @@ nwfilterDefineXML(virConnectPtr conn,
     virNWFilterPtr ret = NULL;
 
     nwfilterDriverLock(driver);
+    virNWFilterWriteLockFilterUpdates();
     virNWFilterCallbackDriversLock();
 
     if (!(def = virNWFilterDefParseString(xml)))
@@ -566,6 +569,7 @@ cleanup:
         virNWFilterObjUnlock(nwfilter);
 
     virNWFilterCallbackDriversUnlock();
+    virNWFilterUnlockFilterUpdates();
     nwfilterDriverUnlock(driver);
     return ret;
 }
@@ -578,10 +582,9 @@ nwfilterUndefine(virNWFilterPtr obj) {
     int ret = -1;
 
     nwfilterDriverLock(driver);
+    virNWFilterWriteLockFilterUpdates();
     virNWFilterCallbackDriversLock();
 
-    virNWFilterLockFilterUpdates();
-
     nwfilter = virNWFilterObjFindByUUID(&driver->nwfilters, obj->uuid);
     if (!nwfilter) {
         virReportError(VIR_ERR_NO_NWFILTER,
@@ -612,9 +615,8 @@ cleanup:
     if (nwfilter)
         virNWFilterObjUnlock(nwfilter);
 
-    virNWFilterUnlockFilterUpdates();
-
     virNWFilterCallbackDriversUnlock();
+    virNWFilterUnlockFilterUpdates();
     nwfilterDriverUnlock(driver);
     return ret;
 }

diff --git a/src/nwfilter/nwfilter_gentech_driver.c b/src/nwfilter/nwfilter_gentech_driver.c
index 637e647fbb82d1f2f236c278b445663fecb2267c..c9ce5142d3527d77598e24b5c56712e78e0bb782 100644 (file)
--- a/src/nwfilter/nwfilter_gentech_driver.c
+++ b/src/nwfilter/nwfilter_gentech_driver.c
@@ -947,8 +947,6 @@ _virNWFilterInstantiateFilter(virNWFilterDriverStatePtr driver,
     int ifindex;
     int rc;
 
-    virNWFilterLockFilterUpdates();
-
     /* after grabbing the filter update lock check for the interface; if
        it's not there anymore its filters will be or are being removed
        (while holding the lock) and we don't want to build new ones */
@@ -976,8 +974,6 @@ _virNWFilterInstantiateFilter(virNWFilterDriverStatePtr driver,
                                         foundNewFilter);
 
 cleanup:
-    virNWFilterUnlockFilterUpdates();
-
     return rc;
 }
 
@@ -996,7 +992,7 @@ virNWFilterInstantiateFilterLate(virNWFilterDriverStatePtr driver,
     int rc;
     bool foundNewFilter = false;
 
-    virNWFilterLockFilterUpdates();
+    virNWFilterReadLockFilterUpdates();
 
     rc = __virNWFilterInstantiateFilter(driver,
                                         vmuuid,

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 8ebfadd68182c5b96503e6151a50d0d780100d01..b209614c0641ea00e9ef5c156db59ff91bad129d 100644 (file)
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -1542,6 +1542,8 @@ static virDomainPtr qemuDomainCreateXML(virConnectPtr conn,
     if (flags & VIR_DOMAIN_START_AUTODESTROY)
         start_flags |= VIR_QEMU_PROCESS_START_AUTODESTROY;
 
+    virNWFilterReadLockFilterUpdates();
+
     if (!(caps = virQEMUDriverGetCapabilities(driver, false)))
         goto cleanup;
 
@@ -1619,6 +1621,7 @@ cleanup:
     }
     virObjectUnref(caps);
     virObjectUnref(qemuCaps);
+    virNWFilterUnlockFilterUpdates();
     return dom;
 }
 
@@ -5846,6 +5849,8 @@ qemuDomainCreateWithFlags(virDomainPtr dom, unsigned int flags)
                   VIR_DOMAIN_START_BYPASS_CACHE |
                   VIR_DOMAIN_START_FORCE_BOOT, -1);
 
+    virNWFilterReadLockFilterUpdates();
+
     if (!(vm = qemuDomObjFromDomain(dom)))
         return -1;
 
@@ -5873,6 +5878,7 @@ endjob:
 cleanup:
     if (vm)
         virObjectUnlock(vm);
+    virNWFilterUnlockFilterUpdates();
     return ret;
 }
 

diff --git a/src/uml/uml_driver.c b/src/uml/uml_driver.c
index 74aa94a69e46985f774fcbbd855b10b333aa06a4..5947082d0cd3fa10bcff87d843a579beb4295f98 100644 (file)
--- a/src/uml/uml_driver.c
+++ b/src/uml/uml_driver.c
@@ -1572,6 +1572,7 @@ static virDomainPtr umlDomainCreateXML(virConnectPtr conn, const char *xml,
 
     virCheckFlags(VIR_DOMAIN_START_AUTODESTROY, NULL);
 
+    virNWFilterReadLockFilterUpdates();
     umlDriverLock(driver);
     if (!(def = virDomainDefParseString(xml, driver->caps, driver->xmlopt,
                                         1 << VIR_DOMAIN_VIRT_UML,
@@ -1611,6 +1612,7 @@ cleanup:
     if (event)
         umlDomainEventQueue(driver, event);
     umlDriverUnlock(driver);
+    virNWFilterUnlockFilterUpdates();
     return dom;
 }
 
@@ -1993,6 +1995,7 @@ static int umlDomainCreateWithFlags(virDomainPtr dom, unsigned int flags) {
 
     virCheckFlags(VIR_DOMAIN_START_AUTODESTROY, -1);
 
+    virNWFilterReadLockFilterUpdates();
     umlDriverLock(driver);
     vm = virDomainObjListFindByUUID(driver->domains, dom->uuid);
 
@@ -2019,6 +2022,7 @@ cleanup:
     if (event)
         umlDomainEventQueue(driver, event);
     umlDriverUnlock(driver);
+    virNWFilterUnlockFilterUpdates();
     return ret;
 }