Re: [PATCH v2 18/24] virNetworkObjFindBy*: Return an reference to found object

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On Fri, Mar 06, 2015 at 11:12:21 +0100, Michal Privoznik wrote:
> On 06.03.2015 10:23, Peter Krempa wrote:
> > On Thu, Mar 05, 2015 at 12:05:19 +0100, Michal Privoznik wrote:
> >> This patch turns both virNetworkObjFindByUUID() and
> >> virNetworkObjFindByName() to return an referenced object so that
> >> even if caller unlocks it, it's for sure that object won't
> >> disappear meanwhile. Especially if the object (in general) is
> >> locked and unlocked during the caller run.
> >> Moreover, this commit is nicely small, since the object unrefing
> >> can be done in virNetworkObjEndAPI().
> >>
> >> Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
> >> ---
> >>  src/conf/network_conf.c     |  7 +++++--
> >>  src/network/bridge_driver.c | 18 +++++-------------
> >>  src/test/test_driver.c      | 10 ++++------
> >>  3 files changed, 14 insertions(+), 21 deletions(-)
> >>
> >> diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
> >> index 7af303e..3d318ce 100644
> >> --- a/src/conf/network_conf.c
> >> +++ b/src/conf/network_conf.c
> >> @@ -137,6 +137,7 @@ virNetworkObjEndAPI(virNetworkObjPtr *net)
> >>          return;
> >>  
> >>      virObjectUnlock(*net);
> >> +    virObjectUnref(*net);
> >>      *net = NULL;
> >>  }
> >>  
> >> @@ -164,6 +165,7 @@ virNetworkObjFindByUUIDLocked(virNetworkObjListPtr nets,
> >>          virObjectLock(nets->objs[i]);
> >>          if (!memcmp(nets->objs[i]->def->uuid, uuid, VIR_UUID_BUFLEN)) {
> >>              ret = nets->objs[i];
> >> +            virObjectRef(ret);
> >>              break;
> >>          }
> >>          virObjectUnlock(nets->objs[i]);
> >> @@ -194,6 +196,7 @@ virNetworkObjFindByNameLocked(virNetworkObjListPtr nets,
> >>          virObjectLock(nets->objs[i]);
> >>          if (STREQ(nets->objs[i]->def->name, name)) {
> >>              ret = nets->objs[i];
> >> +            virObjectRef(ret);
> >>              break;
> >>          }
> >>          virObjectUnlock(nets->objs[i]);
> >> @@ -491,13 +494,13 @@ virNetworkAssignDef(virNetworkObjListPtr nets,
> >>  
> >>      network->def = def;
> >>      network->persistent = !live;
> >> +    virObjectRef(network);
> >>      virObjectUnlock(nets);
> >>      return network;
> >>  
> >>   error:
> >>      virObjectUnlock(nets);
> >> -    virObjectUnlock(network);
> >> -    virObjectUnref(network);
> >> +    virNetworkObjEndAPI(&network);
> >>      return NULL;
> >>  
> >>  }
> >> diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
> >> index 8501603..d3f3f4a 100644
> >> --- a/src/network/bridge_driver.c
> >> +++ b/src/network/bridge_driver.c
> >> @@ -2939,7 +2939,6 @@ static virNetworkPtr networkCreateXML(virConnectPtr conn, const char *xml)
> >>      if (networkStartNetwork(network) < 0) {
> >>          virNetworkRemoveInactive(driver->networks,
> >>                                   network);
> >> -        network = NULL;
> >>          goto cleanup;
> >>      }
> >>  
> >> @@ -2988,7 +2987,6 @@ static virNetworkPtr networkDefineXML(virConnectPtr conn, const char *xml)
> >>      if (virNetworkSaveConfig(driver->networkConfigDir, def) < 0) {
> >>          if (!virNetworkObjIsActive(network)) {
> >>              virNetworkRemoveInactive(driver->networks, network);
> > 
> > As virNetworkRemoveInactive() now doesn't free the object due to the
> > existing reference, but unlocks it ...
> > 
> >> -            network = NULL;
> > 
> > ... and you don't invalidate the pointer, you'd touch the unlocked
> > object in virNetworkObjEndAPI() and try to unlock it once more.
> > 
> >>              goto cleanup;
> >>          }
> >>          /* if network was active already, just undo new persistent
> > 
> > NACK, virNetworkRemoveInactive needs to be fixed first.
> 
> Correct. Nice catch! Would I make you reconsider NACK if I squash this
> into this commit?
> 
> diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
> index 3d318ce..20a257b 100644
> --- a/src/conf/network_conf.c
> +++ b/src/conf/network_conf.c
> @@ -668,17 +668,18 @@ void virNetworkRemoveInactive(virNetworkObjListPtr
> nets,
>  {
>      size_t i;
> 
> +    /* It's not needed to reference the @net as we are called
> +     * from an API which surely already has at least one
> +     * reference to the object. */
>      virObjectUnlock(net);
>      virObjectLock(nets);
> +    virObjectLock(net);
>      for (i = 0; i < nets->count; i++) {
> -        virObjectLock(nets->objs[i]);
>          if (nets->objs[i] == net) {
>              VIR_DELETE_ELEMENT(nets->objs, i, nets->count);
> -            virObjectUnlock(net);
>              virObjectUnref(net);
>              break;
>          }
> -        virObjectUnlock(nets->objs[i]);
>      }
>      virObjectUnlock(nets);
>  }

Fair enough. ACK with the above fixup.

Peter

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