Re: [libvirt] [PATCH 1/2] conf: Rework virDomainObjListFindByUUID to allow more concurrent APIs

Currently, when there is an API that's blocking with locked domain and second API that's waiting in virDomainObjListFindByUUID() for the domain lock (with the domain list locked) no other API can be executed on any domain on the whole hypervisor because all would wait for the domain list to be locked. This patch adds new optional approach to this in which the domain is only ref'd (reference counter is incremented) instead of being locked and is locked *after* the list itself is unlocked. We might consider only ref'ing the domain in the future and leaving locking on particular APIs, but that's no tonight's fairy tale. Signed-off-by: Martin Kletzander <mkletzan(a)redhat.com&gt; --- src/conf/domain_conf.c | 27 ++++++++++++++++++++++++--- src/conf/domain_conf.h | 2 ++ src/libvirt_private.syms | 1 + 3 files changed, 27 insertions(+), 3 deletions(-) diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index 2d81c37..e5bb572 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -1068,8 +1068,10 @@ virDomainObjPtr virDomainObjListFindByID(virDomainObjListPtr doms, } -virDomainObjPtr virDomainObjListFindByUUID(virDomainObjListPtr doms, - const unsigned char *uuid) +static virDomainObjPtr +virDomainObjListFindByUUIDInternal(virDomainObjListPtr doms, + const unsigned char *uuid, + bool ref) { char uuidstr[VIR_UUID_STRING_BUFLEN]; virDomainObjPtr obj; @@ -1078,12 +1080,31 @@ virDomainObjPtr virDomainObjListFindByUUID(virDomainObjListPtr doms, virUUIDFormat(uuid, uuidstr); obj = virHashLookup(doms->objs, uuidstr); + if (ref) { + virObjectRef(obj); + virObjectUnlock(doms); + } if (obj) virObjectLock(obj); - virObjectUnlock(doms); + if (!ref) + virObjectUnlock(doms); return obj; } +virDomainObjPtr +virDomainObjListFindByUUID(virDomainObjListPtr doms, + const unsigned char *uuid) +{ + return virDomainObjListFindByUUIDInternal(doms, uuid, false); +} + +virDomainObjPtr +virDomainObjListFindByUUIDRef(virDomainObjListPtr doms, + const unsigned char *uuid) +{ + return virDomainObjListFindByUUIDInternal(doms, uuid, false);

+} + static int virDomainObjListSearchName(const void *payload, const void *name ATTRIBUTE_UNUSED, const void *data)