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Re: [libvirt] [PATCH 4/5] libvirtd: Alter refcnt processing for server program objects



On Tue, Nov 07, 2017 at 09:39:55PM -0500, John Ferlan wrote:
> Instead of holding onto the reference for each program added to
> a NetServer, let's Unref the program reference as soon as the
> attempt is made to add to the @srv->programs list. This then
> allows the virNetServerDispose to handle the final Unref of
> the object for actual deletion and cleans up the cleanup: path.
>
> Signed-off-by: John Ferlan <jferlan redhat com>
> ---
>  daemon/libvirtd.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/daemon/libvirtd.c b/daemon/libvirtd.c
> index 5c47e49d48..87c5b22710 100644
> --- a/daemon/libvirtd.c
> +++ b/daemon/libvirtd.c
> @@ -1352,7 +1352,10 @@ int main(int argc, char **argv) {
>          ret = VIR_DAEMON_ERR_INIT;
>          goto cleanup;
>      }
> -    if (virNetServerAddProgram(srv, remoteProgram) < 0) {
> +
> +    rc = virNetServerAddProgram(srv, remoteProgram);
> +    virObjectUnref(remoteProgram);

Again, why can't we drop the ref from the AddProgram, if we as the @srv mutex
owners got rescheduled and someone unreff'd @program before we inserted it to
the array (while holding mutex), we'd fail to ref a dangling pointer
consequently, so I don't see any added protection here and I think ^these hunks
are unnecessary, once we agree to drop virObjectRef from virNet<Foo>Add<Bar>
during the init phase.

> +    if (rc < 0) {
>          ret = VIR_DAEMON_ERR_INIT;
>          goto cleanup;
>      }
> @@ -1364,7 +1367,10 @@ int main(int argc, char **argv) {
>          ret = VIR_DAEMON_ERR_INIT;
>          goto cleanup;
>      }
> -    if (virNetServerAddProgram(srv, lxcProgram) < 0) {
> +
> +    rc = virNetServerAddProgram(srv, lxcProgram);
> +    virObjectUnref(lxcProgram);
> +    if (rc < 0) {
>          ret = VIR_DAEMON_ERR_INIT;
>          goto cleanup;
>      }
> @@ -1376,7 +1382,10 @@ int main(int argc, char **argv) {
>          ret = VIR_DAEMON_ERR_INIT;
>          goto cleanup;
>      }
> -    if (virNetServerAddProgram(srv, qemuProgram) < 0) {
> +
> +    rc = virNetServerAddProgram(srv, qemuProgram);
> +    virObjectUnref(qemuProgram);
> +    if (rc < 0) {
>          ret = VIR_DAEMON_ERR_INIT;
>          goto cleanup;
>      }
> @@ -1414,7 +1423,10 @@ int main(int argc, char **argv) {
>          ret = VIR_DAEMON_ERR_INIT;
>          goto cleanup;
>      }
> -    if (virNetServerAddProgram(srvAdm, adminProgram) < 0) {
> +
> +    rc = virNetServerAddProgram(srvAdm, adminProgram);
> +    virObjectUnref(adminProgram);
> +    if (rc < 0) {
>          ret = VIR_DAEMON_ERR_INIT;
>          goto cleanup;
>      }
> @@ -1513,10 +1525,6 @@ int main(int argc, char **argv) {
>
>   cleanup:
>      virNetlinkEventServiceStopAll();
> -    virObjectUnref(remoteProgram);
> -    virObjectUnref(lxcProgram);
> -    virObjectUnref(qemuProgram);
> -    virObjectUnref(adminProgram);

This hunk would stay either way.

Erik


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