From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49757) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aLt2o-0005eW-KZ for qemu-devel@nongnu.org; Wed, 20 Jan 2016 08:43:31 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aLt2j-0000Nm-KB for qemu-devel@nongnu.org; Wed, 20 Jan 2016 08:43:30 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59071) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aLt2j-0000Nb-CK for qemu-devel@nongnu.org; Wed, 20 Jan 2016 08:43:25 -0500 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id 6B3777AE97 for ; Wed, 20 Jan 2016 13:43:24 +0000 (UTC) From: Markus Armbruster References: <1453219845-30939-1-git-send-email-eblake@redhat.com> <1453219845-30939-6-git-send-email-eblake@redhat.com> Date: Wed, 20 Jan 2016 14:43:20 +0100 In-Reply-To: <1453219845-30939-6-git-send-email-eblake@redhat.com> (Eric Blake's message of "Tue, 19 Jan 2016 09:10:13 -0700") Message-ID: <87egdcwemf.fsf@blackfin.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v9 05/37] vl: Improve use of qapi visitor List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: marcandre.lureau@redhat.com, qemu-devel@nongnu.org, Paolo Bonzini Eric Blake writes: > Cache the visitor in a local variable instead of repeatedly > calling the accessor. Pass NULL for the visit_start_struct() > object (which matches the fact that we were already passing 0 > for the size argument, because we aren't using the visit to > allocate a qapi struct). Guarantee that visit_end_struct() > is called if visit_start_struct() succeeded. Three separate things --- you're pushing it now :) Impact of not calling visit_end_struct()? > Signed-off-by: Eric Blake > Reviewed-by: Marc-Andr=C3=A9 Lureau > > --- > v9: no change > v8: no change > v7: place earlier in series, drop attempts to provide a 'kind' string, > drop bogus avoidance of qmp_object_del() on error > v6: new patch, split from RFC on v5 7/46 > --- > vl.c | 26 ++++++++++++++------------ > 1 file changed, 14 insertions(+), 12 deletions(-) > > diff --git a/vl.c b/vl.c > index f043009..aaa5403 100644 > --- a/vl.c > +++ b/vl.c > @@ -2822,44 +2822,47 @@ static bool object_create_delayed(const char *typ= e) > static int object_create(void *opaque, QemuOpts *opts, Error **errp) > { > Error *err =3D NULL; > + Error *err_end =3D NULL; > char *type =3D NULL; > char *id =3D NULL; > - void *dummy =3D NULL; > OptsVisitor *ov; > QDict *pdict; > bool (*type_predicate)(const char *) =3D opaque; > + Visitor *v; > > ov =3D opts_visitor_new(opts); > pdict =3D qemu_opts_to_qdict(opts, NULL); > + v =3D opts_get_visitor(ov); > > - visit_start_struct(opts_get_visitor(ov), &dummy, NULL, NULL, 0, &err= ); > + visit_start_struct(v, NULL, NULL, NULL, 0, &err); Same argument as for the previous patch. > if (err) { > goto out; > } > > qdict_del(pdict, "qom-type"); > - visit_type_str(opts_get_visitor(ov), &type, "qom-type", &err); > + visit_type_str(v, &type, "qom-type", &err); > if (err) { > goto out; > } If we get here, we must call visit_end_struct(). > if (!type_predicate(type)) { > + visit_end_struct(v, NULL); Here, you add the previously missing visit_end_struct() to the error path. > goto out; > } > > qdict_del(pdict, "id"); > - visit_type_str(opts_get_visitor(ov), &id, "id", &err); > + visit_type_str(v, &id, "id", &err); > if (err) { > - goto out; > + goto out_end; Here, you skip to the function's cleanup, which now includes visit_end_struct(). Such a mix is can be a sign the cleanup isn't quite in the right order. When we take this error path to out_end, then: out_end: visit_end_struct(v, &err_end); // called, as we must if (!err && err_end) { // !err is false qmp_object_del(id, NULL); // not called } error_propagate(&err, err_end); // since err, this is // error_free(err_end) > } > > - object_add(type, id, pdict, opts_get_visitor(ov), &err); > - if (err) { > - goto out; > - } > - visit_end_struct(opts_get_visitor(ov), &err); > - if (err) { > + object_add(type, id, pdict, v, &err); > + > +out_end: > + visit_end_struct(v, &err_end); visit_end_struct() must be called when visit_start_struct() succeeded. All error paths after that success pass through here, except for one, and that one calls visit_end_struct(). Okay. > + if (!err && err_end) { > qmp_object_del(id, NULL); > } qmp_object_del() must be called when we fail after object_add() succeeded. That's what the condition does. > + error_propagate(&err, err_end); > > out: Cleanup below here must be done always. > opts_visitor_cleanup(ov); The only reason I'm not asking you to rewrite this mess is that you're already rewriting it later in this series. > @@ -2867,7 +2870,6 @@ out: > QDECREF(pdict); > g_free(id); > g_free(type); > - g_free(dummy); > if (err) { > error_report_err(err); > return -1; I wonder whether splitting this and the previous patch along the change rather than the file would come out nicer: 1. Cache the visitor 2. Suppress the pointless allocation 3. Fix to call visit_end_struct()