From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: Re: [PATCH] cgroup: use uninitialized_var() for may-be uninitialized variable Date: Tue, 22 Apr 2014 14:26:43 +0800 Message-ID: <53560BA3.40501@huawei.com> References: <1398145479-11400-1-git-send-email-nasa4836@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <1398145479-11400-1-git-send-email-nasa4836-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Jianyu Zhan Cc: tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org T24gMjAxNC80LzIyIDEzOjQ0LCBKaWFueXUgWmhhbiB3cm90ZToKPiBUbyBzdXBwcmVzcyB0aGlz IHdhcm5pbmc6Cj4gCj4gIHdhcm5pbmc6IOKAmGVycuKAmSBtYXkgYmUgdXNlZCB1bmluaXRpYWxp emVkIGluIHRoaXMgZnVuY3Rpb24gWy1XbWF5YmUtdW5pbml0aWFsaXplZF0KPiAgIGludCBlcnI7 Cj4gCV4KCkkgZG9uJ3Qgc2VlIHRoaXMgd2FybmluZywgYW5kIEkgZG9uJ3Qgc2VlIGhvdyB0aGlz IGlzIHBvc3NpYmxlLgoKc3RhdGljIGludCBjcmVhdGVfY3NzKHN0cnVjdCBjZ3JvdXAgKmNncnAs IHN0cnVjdCBjZ3JvdXBfc3Vic3lzICpzcykKewoJc3RydWN0IGNncm91cCAqcGFyZW50ID0gY2dy cC0+cGFyZW50OwoJc3RydWN0IGNncm91cF9zdWJzeXNfc3RhdGUgKmNzczsKCWludCBlcnI7CgoJ bG9ja2RlcF9hc3NlcnRfaGVsZCgmY2dyb3VwX211dGV4KTsKCgljc3MgPSBzcy0+Y3NzX2FsbG9j KGNncm91cF9jc3MocGFyZW50LCBzcykpOwoJaWYgKElTX0VSUihjc3MpKQoJCXJldHVybiBQVFJf RVJSKGNzcyk7CgoJZXJyID0gcGVyY3B1X3JlZl9pbml0KCZjc3MtPnJlZmNudCwgY3NzX3JlbGVh c2UpOwoJaWYgKGVycikKCQlnb3RvIGVycl9mcmVlX2NzczsKCS4uLgoKCXJldHVybiBlcnI7Cn0K Cj4gCj4gVXNlIHRoZSB1bmluaXRpYWxpemVkX3ZhcigpIHRvIGRlY2FscmUgZXJyLiBJdCBhbHNv IHNlcnZlcyB0byBiZSBnb29kIGRvY3VtZXRhdGlvbi4KPiAKCmFueXdheSwgdW5pbml0aWFsaXpl ZF92YXIoKSBzaG91bGQgYmUgYXZvaWRlZCBpZiBwb3NzaWJsZS4KCm5hY2sKCj4gU2lnbmVkLW9m Zi1ieTogSmlhbnl1IFpoYW4gPG5hc2E0ODM2QGdtYWlsLmNvbT4KPiAtLS0KPiAga2VybmVsL2Nn cm91cC5jIHwgMiArLQo+ICAxIGZpbGUgY2hhbmdlZCwgMSBpbnNlcnRpb24oKyksIDEgZGVsZXRp b24oLSkKPiAKPiBkaWZmIC0tZ2l0IGEva2VybmVsL2Nncm91cC5jIGIva2VybmVsL2Nncm91cC5j Cj4gaW5kZXggMjQ2NzVmNS4uOTMwNTY5YyAxMDA2NDQKPiAtLS0gYS9rZXJuZWwvY2dyb3VwLmMK PiArKysgYi9rZXJuZWwvY2dyb3VwLmMKPiBAQCAtNDE0NCw3ICs0MTQ0LDcgQEAgc3RhdGljIGlu dCBjcmVhdGVfY3NzKHN0cnVjdCBjZ3JvdXAgKmNncnAsIHN0cnVjdCBjZ3JvdXBfc3Vic3lzICpz cykKPiAgewo+ICAJc3RydWN0IGNncm91cCAqcGFyZW50ID0gY2dycC0+cGFyZW50Owo+ICAJc3Ry dWN0IGNncm91cF9zdWJzeXNfc3RhdGUgKmNzczsKPiAtCWludCBlcnI7Cj4gKwlpbnQgdW5pbml0 aWFsaXplZF92YXIoZXJyKTsKPiAgCj4gIAlsb2NrZGVwX2Fzc2VydF9oZWxkKCZjZ3JvdXBfbXV0 ZXgpOwo+ICAKPiAKCl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fCkNvbnRhaW5lcnMgbWFpbGluZyBsaXN0CkNvbnRhaW5lcnNAbGlzdHMubGludXgtZm91bmRh dGlvbi5vcmcKaHR0cHM6Ly9saXN0cy5saW51eGZvdW5kYXRpb24ub3JnL21haWxtYW4vbGlzdGlu Zm8vY29udGFpbmVycw== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752010AbaDVG1v (ORCPT ); Tue, 22 Apr 2014 02:27:51 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:1319 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750756AbaDVG1r (ORCPT ); Tue, 22 Apr 2014 02:27:47 -0400 Message-ID: <53560BA3.40501@huawei.com> Date: Tue, 22 Apr 2014 14:26:43 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Jianyu Zhan CC: , , , Subject: Re: [PATCH] cgroup: use uninitialized_var() for may-be uninitialized variable References: <1398145479-11400-1-git-send-email-nasa4836@gmail.com> In-Reply-To: <1398145479-11400-1-git-send-email-nasa4836@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.177.18.230] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014/4/22 13:44, Jianyu Zhan wrote: > To suppress this warning: > > warning: ‘err’ may be used uninitialized in this function [-Wmaybe-uninitialized] > int err; > ^ I don't see this warning, and I don't see how this is possible. static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss) { struct cgroup *parent = cgrp->parent; struct cgroup_subsys_state *css; int err; lockdep_assert_held(&cgroup_mutex); css = ss->css_alloc(cgroup_css(parent, ss)); if (IS_ERR(css)) return PTR_ERR(css); err = percpu_ref_init(&css->refcnt, css_release); if (err) goto err_free_css; ... return err; } > > Use the uninitialized_var() to decalre err. It also serves to be good documetation. > anyway, uninitialized_var() should be avoided if possible. nack > Signed-off-by: Jianyu Zhan > --- > kernel/cgroup.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > index 24675f5..930569c 100644 > --- a/kernel/cgroup.c > +++ b/kernel/cgroup.c > @@ -4144,7 +4144,7 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss) > { > struct cgroup *parent = cgrp->parent; > struct cgroup_subsys_state *css; > - int err; > + int uninitialized_var(err); > > lockdep_assert_held(&cgroup_mutex); > >