From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3FF19C3A5A6 for ; Thu, 19 Sep 2019 07:55:01 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0868321A4C for ; Thu, 19 Sep 2019 07:55:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0868321A4C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:39866 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iArHI-0007X9-5N for qemu-devel@archiver.kernel.org; Thu, 19 Sep 2019 03:55:00 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58941) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iArGK-0006eK-IS for qemu-devel@nongnu.org; Thu, 19 Sep 2019 03:54:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iArGI-0001TO-Qu for qemu-devel@nongnu.org; Thu, 19 Sep 2019 03:54:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35322) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iArGA-0001OT-Ik; Thu, 19 Sep 2019 03:53:50 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id CC77FC057EC0; Thu, 19 Sep 2019 07:53:48 +0000 (UTC) Received: from [10.36.117.104] (ovpn-117-104.ams2.redhat.com [10.36.117.104]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5E8F95C548; Thu, 19 Sep 2019 07:53:25 +0000 (UTC) To: Vladimir Sementsov-Ogievskiy , "qemu-devel@nongnu.org" References: <20190918130244.24257-1-vsementsov@virtuozzo.com> <9d7ae167-c77c-4d8a-bbbc-c33a03a115e5@virtuozzo.com> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwX4EEwECACgFAljj9eoCGwMFCQlmAYAGCwkI BwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEE3eEPcA/4Na5IIP/3T/FIQMxIfNzZshIq687qgG 8UbspuE/YSUDdv7r5szYTK6KPTlqN8NAcSfheywbuYD9A4ZeSBWD3/NAVUdrCaRP2IvFyELj xoMvfJccbq45BxzgEspg/bVahNbyuBpLBVjVWwRtFCUEXkyazksSv8pdTMAs9IucChvFmmq3 jJ2vlaz9lYt/lxN246fIVceckPMiUveimngvXZw21VOAhfQ+/sofXF8JCFv2mFcBDoa7eYob s0FLpmqFaeNRHAlzMWgSsP80qx5nWWEvRLdKWi533N2vC/EyunN3HcBwVrXH4hxRBMco3jvM m8VKLKao9wKj82qSivUnkPIwsAGNPdFoPbgghCQiBjBe6A75Z2xHFrzo7t1jg7nQfIyNC7ez MZBJ59sqA9EDMEJPlLNIeJmqslXPjmMFnE7Mby/+335WJYDulsRybN+W5rLT5aMvhC6x6POK z55fMNKrMASCzBJum2Fwjf/VnuGRYkhKCqqZ8gJ3OvmR50tInDV2jZ1DQgc3i550T5JDpToh dPBxZocIhzg+MBSRDXcJmHOx/7nQm3iQ6iLuwmXsRC6f5FbFefk9EjuTKcLMvBsEx+2DEx0E UnmJ4hVg7u1PQ+2Oy+Lh/opK/BDiqlQ8Pz2jiXv5xkECvr/3Sv59hlOCZMOaiLTTjtOIU7Tq 7ut6OL64oAq+zsFNBFXLn5EBEADn1959INH2cwYJv0tsxf5MUCghCj/CA/lc/LMthqQ773ga uB9mN+F1rE9cyyXb6jyOGn+GUjMbnq1o121Vm0+neKHUCBtHyseBfDXHA6m4B3mUTWo13nid 0e4AM71r0DS8+KYh6zvweLX/LL5kQS9GQeT+QNroXcC1NzWbitts6TZ+IrPOwT1hfB4WNC+X 2n4AzDqp3+ILiVST2DT4VBc11Gz6jijpC/KI5Al8ZDhRwG47LUiuQmt3yqrmN63V9wzaPhC+ xbwIsNZlLUvuRnmBPkTJwwrFRZvwu5GPHNndBjVpAfaSTOfppyKBTccu2AXJXWAE1Xjh6GOC 8mlFjZwLxWFqdPHR1n2aPVgoiTLk34LR/bXO+e0GpzFXT7enwyvFFFyAS0Nk1q/7EChPcbRb hJqEBpRNZemxmg55zC3GLvgLKd5A09MOM2BrMea+l0FUR+PuTenh2YmnmLRTro6eZ/qYwWkC u8FFIw4pT0OUDMyLgi+GI1aMpVogTZJ70FgV0pUAlpmrzk/bLbRkF3TwgucpyPtcpmQtTkWS gDS50QG9DR/1As3LLLcNkwJBZzBG6PWbvcOyrwMQUF1nl4SSPV0LLH63+BrrHasfJzxKXzqg rW28CTAE2x8qi7e/6M/+XXhrsMYG+uaViM7n2je3qKe7ofum3s4vq7oFCPsOgwARAQABwsFl BBgBAgAPBQJVy5+RAhsMBQkJZgGAAAoJEE3eEPcA/4NagOsP/jPoIBb/iXVbM+fmSHOjEshl KMwEl/m5iLj3iHnHPVLBUWrXPdS7iQijJA/VLxjnFknhaS60hkUNWexDMxVVP/6lbOrs4bDZ NEWDMktAeqJaFtxackPszlcpRVkAs6Msn9tu8hlvB517pyUgvuD7ZS9gGOMmYwFQDyytpepo YApVV00P0u3AaE0Cj/o71STqGJKZxcVhPaZ+LR+UCBZOyKfEyq+ZN311VpOJZ1IvTExf+S/5 lqnciDtbO3I4Wq0ArLX1gs1q1XlXLaVaA3yVqeC8E7kOchDNinD3hJS4OX0e1gdsx/e6COvy qNg5aL5n0Kl4fcVqM0LdIhsubVs4eiNCa5XMSYpXmVi3HAuFyg9dN+x8thSwI836FoMASwOl C7tHsTjnSGufB+D7F7ZBT61BffNBBIm1KdMxcxqLUVXpBQHHlGkbwI+3Ye+nE6HmZH7IwLwV W+Ajl7oYF+jeKaH4DZFtgLYGLtZ1LDwKPjX7VAsa4Yx7S5+EBAaZGxK510MjIx6SGrZWBrrV TEvdV00F2MnQoeXKzD7O4WFbL55hhyGgfWTHwZ457iN9SgYi1JLPqWkZB0JRXIEtjd4JEQcx +8Umfre0Xt4713VxMygW0PnQt5aSQdMD58jHFxTk092mU+yIHj5LeYgvwSgZN4airXk5yRXl SE+xAvmumFBY Organization: Red Hat GmbH Message-ID: <0764e9fc-b0ff-12c7-fffb-adf68706383b@redhat.com> Date: Thu, 19 Sep 2019 09:53:24 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <9d7ae167-c77c-4d8a-bbbc-c33a03a115e5@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Thu, 19 Sep 2019 07:53:49 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [RFC] error: auto propagated local_err X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "fam@euphon.net" , "peter.maydell@linaro.org" , "mst@redhat.com" , "codyprime@gmail.com" , "mark.cave-ayland@ilande.co.uk" , "mdroth@linux.vnet.ibm.com" , "kraxel@redhat.com" , "mreitz@redhat.com" , "qemu-block@nongnu.org" , "quintela@redhat.com" , "armbru@redhat.com" , "pasic@linux.ibm.com" , "borntraeger@de.ibm.com" , "marcandre.lureau@redhat.com" , "rth@twiddle.net" , "farman@linux.ibm.com" , "groug@kaod.org" , "dgilbert@redhat.com" , "alex.williamson@redhat.com" , "qemu-arm@nongnu.org" , "stefanha@redhat.com" , "jsnow@redhat.com" , "david@gibson.dropbear.id.au" , "kwolf@redhat.com" , "berrange@redhat.com" , "cohuck@redhat.com" , "qemu-s390x@nongnu.org" , "sundeep.lkml@gmail.com" , "qemu-ppc@nongnu.org" , "pbonzini@redhat.com" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 19.09.19 09:41, Vladimir Sementsov-Ogievskiy wrote: > 19.09.2019 10:32, David Hildenbrand wrote: >> On 18.09.19 15:02, Vladimir Sementsov-Ogievskiy wrote: >>> Hi all! >>> >>> Here is a proposal (three of them, actually) of auto propagation for >>> local_err, to not call error_propagate on every exit point, when we >>> deal with local_err. >>> >>> It also may help make Greg's series[1] about error_append_hint smaller. >>> >>> See definitions and examples below. >>> >>> I'm cc-ing to this RFC everyone from series[1] CC list, as if we like >>> it, the idea will touch same code (and may be more). >>> >>> [1]: https://lists.gnu.org/archive/html/qemu-devel/2019-09/msg03449.html >>> >>> Signed-off-by: Vladimir Sementsov-Ogievskiy >>> --- >>> include/qapi/error.h | 102 +++++++++++++++++++++++++++++++++++++++++++ >>> block.c | 63 ++++++++++++-------------- >>> block/backup.c | 8 +++- >>> block/gluster.c | 7 +++ >>> 4 files changed, 144 insertions(+), 36 deletions(-) >>> >>> diff --git a/include/qapi/error.h b/include/qapi/error.h >>> index 3f95141a01..083e061014 100644 >>> --- a/include/qapi/error.h >>> +++ b/include/qapi/error.h >>> @@ -322,6 +322,108 @@ void error_set_internal(Error **errp, >>> ErrorClass err_class, const char *fmt, ...) >>> GCC_FMT_ATTR(6, 7); >>> >>> +typedef struct ErrorPropagator { >>> + Error **errp; >>> + Error *local_err; >>> +} ErrorPropagator; >>> + >>> +static inline void error_propagator_cleanup(ErrorPropagator *prop) >>> +{ >>> + if (prop->local_err) { >>> + error_propagate(prop->errp, prop->local_err); >>> + } >>> +} >>> + >>> +G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(ErrorPropagator, error_propagator_cleanup); >>> + >>> +/* >>> + * ErrorPropagationPair >>> + * >>> + * [Error *local_err, Error **errp] >>> + * >>> + * First element is local_err, second is original errp, which is propagation >>> + * target. Yes, errp has a bit another type, so it should be converted. >>> + * >>> + * ErrorPropagationPair may be used as errp, which points to local_err, >>> + * as it's type is compatible. >>> + */ >>> +typedef Error *ErrorPropagationPair[2]; >>> + >>> +static inline void error_propagation_pair_cleanup(ErrorPropagationPair *arr) >>> +{ >>> + Error *local_err = (*arr)[0]; >>> + Error **errp = (Error **)(*arr)[1]; >>> + >>> + if (local_err) { >>> + error_propagate(errp, local_err); >>> + } >>> +} >>> + >>> +G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(ErrorPropagationPair, >>> + error_propagation_pair_cleanup); >>> + >>> +/* >>> + * DEF_AUTO_ERRP >>> + * >>> + * Define auto_errp variable, which may be used instead of errp, and >>> + * *auto_errp may be safely checked to be zero or not, and may be safely >>> + * used for error_append_hint(). auto_errp is automatically propagated >>> + * to errp at function exit. >>> + */ >>> +#define DEF_AUTO_ERRP(auto_errp, errp) \ >>> + g_auto(ErrorPropagationPair) (auto_errp) = {NULL, (Error *)(errp)} >>> + >>> + >>> +/* >>> + * Another variant: >>> + * Pros: >>> + * - normal structure instead of cheating with array >>> + * - we can directly use errp, if it's not NULL and don't point to >>> + * error_abort or error_fatal >>> + * Cons: >>> + * - we need to define two variables instead of one >>> + */ >>> +typedef struct ErrorPropagationStruct { >>> + Error *local_err; >>> + Error **errp; >>> +} ErrorPropagationStruct; >>> + >>> +static inline void error_propagation_struct_cleanup(ErrorPropagationStruct *prop) >>> +{ >>> + if (prop->local_err) { >>> + error_propagate(prop->errp, prop->local_err); >>> + } >>> +} >>> + >>> +G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(ErrorPropagationStruct, >>> + error_propagation_struct_cleanup); >>> + >>> +#define DEF_AUTO_ERRP_V2(auto_errp, errp) \ >>> + g_auto(ErrorPropagationStruct) (__auto_errp_prop) = {.errp = (errp)}; \ >>> + Error **auto_errp = \ >>> + ((errp) == NULL || *(errp) == error_abort || *(errp) == error_fatal) ? \ >>> + &__auto_errp_prop.local_err : \ >>> + (errp); >>> + >>> +/* >>> + * Third variant: >>> + * Pros: >>> + * - simpler movement for functions which don't have local_err yet >>> + * the only thing to do is to call one macro at function start. >>> + * This extremely simplifies Greg's series >>> + * Cons: >>> + * - looks like errp shadowing.. Still seems safe. >>> + * - must be after all definitions of local variables and before any >>> + * code. >>> + * - like v2, several statements in one open macro >>> + */ >>> +#define MAKE_ERRP_SAFE(errp) \ >>> +g_auto(ErrorPropagationStruct) (__auto_errp_prop) = {.errp = (errp)}; \ >>> +if ((errp) == NULL || *(errp) == error_abort || *(errp) == error_fatal) { \ >>> + (errp) = &__auto_errp_prop.local_err; \ >>> +} >> >> >> Using that idea, what about something like this: >> >> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c >> index 8bfb6684cb..043ad69f8b 100644 >> --- a/hw/s390x/s390-virtio-ccw.c >> +++ b/hw/s390x/s390-virtio-ccw.c >> @@ -58,22 +58,42 @@ S390CPU *s390_cpu_addr2state(uint16_t cpu_addr) >> return S390_CPU(ms->possible_cpus->cpus[cpu_addr].cpu); >> } >> >> +typedef struct ErrorPropagator { >> + Error **errp; >> + Error *local_err; >> +} ErrorPropagator; >> + >> +static inline void error_propagator_cleanup(ErrorPropagator *prop) >> +{ >> + if (prop->local_err) { >> + error_propagate(prop->errp, prop->local_err); >> + } >> +} >> + >> +G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(ErrorPropagator, error_propagator_cleanup); >> + >> +#define DEFINE_LOCAL_ERRP(_errp) \ >> +g_auto(ErrorPropagator) (__auto_errp_prop) = {.errp = (_errp)}; \ >> +Error **local_errp = &__auto_errp_prop.local_err >> + >> static S390CPU *s390x_new_cpu(const char *typename, uint32_t core_id, >> Error **errp) >> { >> + DEFINE_LOCAL_ERRP(errp); >> S390CPU *cpu = S390_CPU(object_new(typename)); >> - Error *err = NULL; >> >> - object_property_set_int(OBJECT(cpu), core_id, "core-id", &err); >> - if (err != NULL) { >> + object_property_set_int(OBJECT(cpu), core_id, "core-id", local_errp); >> + if (*local_errp != NULL) { >> goto out; >> } >> - object_property_set_bool(OBJECT(cpu), true, "realized", &err); >> + object_property_set_bool(OBJECT(cpu), true, "realized", local_errp); >> >> out: >> object_unref(OBJECT(cpu)); >> - if (err) { >> - error_propagate(errp, err); >> + if (*local_errp) { >> cpu = NULL; >> } >> return cpu; >> >> > > So it's DEF_AUTO_ERRP_V2 with first parameter hardcoded to be local_errp. > I still prefer MAKE_ERRP_SAFE(), to not introduce extra variables. > I lost track of the different approaches ;) The local variable will most probably optimized out by the compiler. I dislike MAKE_ERRP_SAFE(), as it mixes defining a new variable with code. -- Thanks, David / dhildenb