From 6e5c79a1b5a8b3a23e7df7ffe58fb272aa17fbfb Mon Sep 17 00:00:00 2001 From: "Daniel P. Berrange" Date: Wed, 22 Jan 2014 17:28:29 +0000 Subject: [PATCH] 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 --- src/conf/nwfilter_conf.c | 23 +++++++++++------------ src/conf/nwfilter_conf.h | 3 ++- src/libvirt_private.syms | 3 ++- src/lxc/lxc_driver.c | 6 ++++++ src/nwfilter/nwfilter_driver.c | 10 ++++++---- src/nwfilter/nwfilter_gentech_driver.c | 6 +----- src/qemu/qemu_driver.c | 6 ++++++ src/uml/uml_driver.c | 4 ++++ 8 files changed, 38 insertions(+), 23 deletions(-) diff --git a/src/conf/nwfilter_conf.c b/src/conf/nwfilter_conf.c index 6db8ea9fbf..52e1c06231 100644 --- a/src/conf/nwfilter_conf.c +++ b/src/conf/nwfilter_conf.c @@ -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); } @@ -2990,14 +2995,12 @@ 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; } @@ -3005,7 +3008,6 @@ virNWFilterObjAssignDef(virNWFilterObjListPtr nwfilters, /* trigger the update on VMs referencing the filter */ if (virNWFilterTriggerVMFilterRebuild()) { nwfilter->newDef = NULL; - virNWFilterUnlockFilterUpdates(); virNWFilterObjUnlock(nwfilter); return NULL; } @@ -3013,12 +3015,9 @@ virNWFilterObjAssignDef(virNWFilterObjListPtr nwfilters, virNWFilterDefFree(nwfilter->def); nwfilter->def = def; nwfilter->newDef = NULL; - virNWFilterUnlockFilterUpdates(); return nwfilter; } - virNWFilterUnlockFilterUpdates(); - if (VIR_ALLOC(nwfilter) < 0) return NULL; @@ -3483,7 +3482,7 @@ int virNWFilterConfLayerInit(virDomainObjListIterator domUpdateCB, initialized = true; - if (virMutexInitRecursive(&updateMutex) < 0) + if (virRWLockInit(&updateLock) < 0) return -1; return 0; @@ -3495,7 +3494,7 @@ 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 6b8b515500..0d09b6a7d3 100644 --- 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 94901c7ef0..1a8d08852f 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -575,7 +575,6 @@ virNWFilterDefParseString; virNWFilterInstFiltersOnAllVMs; virNWFilterJumpTargetTypeToString; virNWFilterLoadAllConfigs; -virNWFilterLockFilterUpdates; virNWFilterObjAssignDef; virNWFilterObjDeleteDef; virNWFilterObjFindByName; @@ -587,6 +586,7 @@ virNWFilterObjSaveDef; virNWFilterObjUnlock; virNWFilterPrintStateMatchFlags; virNWFilterPrintTCPFlags; +virNWFilterReadLockFilterUpdates; virNWFilterRegisterCallbackDriver; virNWFilterRuleActionTypeToString; virNWFilterRuleDirectionTypeToString; @@ -594,6 +594,7 @@ virNWFilterRuleProtocolTypeToString; virNWFilterTestUnassignDef; virNWFilterUnlockFilterUpdates; virNWFilterUnRegisterCallbackDriver; +virNWFilterWriteLockFilterUpdates; # conf/nwfilter_ipaddrmap.h diff --git a/src/lxc/lxc_driver.c b/src/lxc/lxc_driver.c index 982f3fc8c6..73a2986710 100644 --- a/src/lxc/lxc_driver.c +++ b/src/lxc/lxc_driver.c @@ -1015,6 +1015,8 @@ static int lxcDomainCreateWithFiles(virDomainPtr dom, virCheckFlags(VIR_DOMAIN_START_AUTODESTROY, -1); + virNWFilterReadLockFilterUpdates(); + if (!(vm = lxcDomObjFromDomain(dom))) goto cleanup; @@ -1053,6 +1055,7 @@ cleanup: if (event) virObjectEventStateQueue(driver->domainEventState, event); virObjectUnref(cfg); + virNWFilterUnlockFilterUpdates(); return ret; } @@ -1109,6 +1112,8 @@ lxcDomainCreateXMLWithFiles(virConnectPtr conn, virCheckFlags(VIR_DOMAIN_START_AUTODESTROY, NULL); + virNWFilterReadLockFilterUpdates(); + if (!(caps = virLXCDriverGetCapabilities(driver, false))) goto cleanup; @@ -1164,6 +1169,7 @@ cleanup: virObjectEventStateQueue(driver->domainEventState, event); virObjectUnref(caps); virObjectUnref(cfg); + virNWFilterUnlockFilterUpdates(); return dom; } diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c index d21dd82ac5..5908df723c 100644 --- a/src/nwfilter/nwfilter_driver.c +++ b/src/nwfilter/nwfilter_driver.c @@ -283,12 +283,14 @@ nwfilterStateReload(void) virNWFilterLearnThreadsTerminate(true); nwfilterDriverLock(driverState); + virNWFilterWriteLockFilterUpdates(); virNWFilterCallbackDriversLock(); virNWFilterLoadAllConfigs(&driverState->nwfilters, driverState->configDir); virNWFilterCallbackDriversUnlock(); + virNWFilterUnlockFilterUpdates(); nwfilterDriverUnlock(driverState); virNWFilterInstFiltersOnAllVMs(); @@ -554,6 +556,7 @@ nwfilterDefineXML(virConnectPtr conn, virNWFilterPtr ret = NULL; nwfilterDriverLock(driver); + virNWFilterWriteLockFilterUpdates(); virNWFilterCallbackDriversLock(); if (!(def = virNWFilterDefParseString(xml))) @@ -580,6 +583,7 @@ cleanup: virNWFilterObjUnlock(nwfilter); virNWFilterCallbackDriversUnlock(); + virNWFilterUnlockFilterUpdates(); nwfilterDriverUnlock(driver); return ret; } @@ -592,10 +596,9 @@ nwfilterUndefine(virNWFilterPtr obj) { int ret = -1; nwfilterDriverLock(driver); + virNWFilterWriteLockFilterUpdates(); virNWFilterCallbackDriversLock(); - virNWFilterLockFilterUpdates(); - nwfilter = virNWFilterObjFindByUUID(&driver->nwfilters, obj->uuid); if (!nwfilter) { virReportError(VIR_ERR_NO_NWFILTER, @@ -626,9 +629,8 @@ 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 89913cf848..8c5cd57b61 100644 --- a/src/nwfilter/nwfilter_gentech_driver.c +++ b/src/nwfilter/nwfilter_gentech_driver.c @@ -935,8 +935,6 @@ _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 */ @@ -964,8 +962,6 @@ _virNWFilterInstantiateFilter(virNWFilterDriverStatePtr driver, foundNewFilter); cleanup: - virNWFilterUnlockFilterUpdates(); - return rc; } @@ -984,7 +980,7 @@ 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 6b3825aed0..0128356db5 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -1576,6 +1576,8 @@ 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; @@ -1656,6 +1658,7 @@ cleanup: } virObjectUnref(caps); virObjectUnref(qemuCaps); + virNWFilterUnlockFilterUpdates(); return dom; } @@ -6095,6 +6098,8 @@ qemuDomainCreateWithFlags(virDomainPtr dom, unsigned int flags) VIR_DOMAIN_START_BYPASS_CACHE | VIR_DOMAIN_START_FORCE_BOOT, -1); + virNWFilterReadLockFilterUpdates(); + if (!(vm = qemuDomObjFromDomain(dom))) return -1; @@ -6122,6 +6127,7 @@ endjob: cleanup: if (vm) virObjectUnlock(vm); + virNWFilterUnlockFilterUpdates(); return ret; } diff --git a/src/uml/uml_driver.c b/src/uml/uml_driver.c index 89afefef2e..309c10e95a 100644 --- a/src/uml/uml_driver.c +++ b/src/uml/uml_driver.c @@ -1574,6 +1574,7 @@ 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, @@ -1613,6 +1614,7 @@ cleanup: if (event) umlDomainEventQueue(driver, event); umlDriverUnlock(driver); + virNWFilterUnlockFilterUpdates(); return dom; } @@ -1997,6 +1999,7 @@ static int umlDomainCreateWithFlags(virDomainPtr dom, unsigned int flags) { virCheckFlags(VIR_DOMAIN_START_AUTODESTROY, -1); + virNWFilterReadLockFilterUpdates(); umlDriverLock(driver); vm = virDomainObjListFindByUUID(driver->domains, dom->uuid); @@ -2023,6 +2026,7 @@ cleanup: if (event) umlDomainEventQueue(driver, event); umlDriverUnlock(driver); + virNWFilterUnlockFilterUpdates(); return ret; }