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=-5.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_SBL,URIBL_SBL_A 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 799E8C43603 for ; Wed, 4 Dec 2019 15:03:41 +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 1255D2084F for ; Wed, 4 Dec 2019 15:03:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="A+ywdV5W" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1255D2084F 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]:40122 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1icWBo-0001Nt-7q for qemu-devel@archiver.kernel.org; Wed, 04 Dec 2019 10:03:40 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:48404) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1icW91-0007xG-6j for qemu-devel@nongnu.org; Wed, 04 Dec 2019 10:00:55 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1icW8x-0000MF-Py for qemu-devel@nongnu.org; Wed, 04 Dec 2019 10:00:47 -0500 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:39682 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1icW8x-0000Ln-KR for qemu-devel@nongnu.org; Wed, 04 Dec 2019 10:00:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1575471643; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ajRfpg8Ys2mundddq1XB+ae7HTn9RvM1JIztRsA+x88=; b=A+ywdV5WHf3FBI4ktUXu7ICSEbE2SacHxC4AkvV9WKIb3dyCmtID2cVDscbs0Fn9sWUDTD fxe0NTe1r9dfbgsz9680THTB8UqzJaYENPIqd5zPevHmvkcBuEmhTVqmgu0XZW7+ehi12h kOBG0WhgeB5AJspWzLTjoBwbbVH88Fk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-121-mtHk5eY3O-2_dbJ5ZdlsaQ-1; Wed, 04 Dec 2019 10:00:40 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D568618557FF; Wed, 4 Dec 2019 15:00:36 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-116-134.ams2.redhat.com [10.36.116.134]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4E41E19C68; Wed, 4 Dec 2019 15:00:01 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id C11E51138606; Wed, 4 Dec 2019 15:59:59 +0100 (CET) From: Markus Armbruster To: Vladimir Sementsov-Ogievskiy Subject: Re: [RFC v5 024/126] error: auto propagated local_err References: <20191011160552.22907-1-vsementsov@virtuozzo.com> <20191011160552.22907-25-vsementsov@virtuozzo.com> Date: Wed, 04 Dec 2019 15:59:59 +0100 In-Reply-To: <20191011160552.22907-25-vsementsov@virtuozzo.com> (Vladimir Sementsov-Ogievskiy's message of "Fri, 11 Oct 2019 19:04:10 +0300") Message-ID: <87muc8p24w.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: mtHk5eY3O-2_dbJ5ZdlsaQ-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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: Ronnie Sahlberg , Jeff Cody , Jan Kiszka , Alberto Garcia , Hailiang Zhang , qemu-block@nongnu.org, Aleksandar Rikalo , Halil Pasic , =?utf-8?Q?Herv=C3=A9?= Poussineau , Anthony Perard , Samuel Thibault , Laszlo Ersek , Jason Wang , Laurent Vivier , Eduardo Habkost , Xie Changlong , Peter Lieven , "Dr. David Alan Gilbert" , Beniamino Galvani , Eric Auger , Alex Williamson , Stefan Hajnoczi , John Snow , Richard Henderson , Kevin Wolf , Andrew Jeffery , Chris Wulff , Subbaraya Sundeep , Michael Walle , qemu-ppc@nongnu.org, Bastian Koppelmann , Igor Mammedov , Fam Zheng , Peter Maydell , sheepdog@lists.wpkg.org, Matthew Rosato , David Hildenbrand , Palmer Dabbelt , Eric Farman , Max Filippov , "Denis V. Lunev" , Hannes Reinecke , Stefano Stabellini , "Gonglei \(Arei\)" , Liu Yuan , Artyom Tarasenko , Thomas Huth , Amit Shah , Stefan Weil , Greg Kurz , Yuval Shaia , qemu-s390x@nongnu.org, qemu-arm@nongnu.org, Peter Chubb , =?utf-8?Q?C=C3=A9dric?= Le Goater , Stafford Horne , qemu-riscv@nongnu.org, Cornelia Huck , Aleksandar Markovic , Aurelien Jarno , Paul Burton , Sagar Karandikar , Paul Durrant , Anthony Green , Gerd Hoffmann , "Edgar E. Iglesias" , Guan Xuetao , Ari Sundholm , Juan Quintela , Michael Roth , Christian Borntraeger , Joel Stanley , Jason Dillaman , Antony Pavlov , xen-devel@lists.xenproject.org, integration@gluster.org, Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , "Richard W.M. Jones" , Andrew Baumann , Max Reitz , "Michael S. Tsirkin" , Mark Cave-Ayland , qemu-devel@nongnu.org, Vincenzo Maffione , Marek Vasut , armbru@redhat.com, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Alistair Francis , Pavel Dovgalyuk , Giuseppe Lettieri , Luigi Rizzo , David Gibson , Tony Krowiak , "Daniel P. =?utf-8?Q?Berrang=C3=A9?=" , Xiao Guangrong , Pierre Morel , Wen Congyang , Jean-Christophe Dubois , Paolo Bonzini , Stefan Berger Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Archived-At: List-Archive: Vladimir Sementsov-Ogievskiy writes: > Here is introduced ERRP_AUTO_PROPAGATE macro, to be used at start of > functions with errp OUT parameter. > > It has three goals: > > 1. Fix issue with error_fatal & error_prepend/error_append_hint: user > can't see this additional information, because exit() happens in > error_setg earlier than information is added. [Reported by Greg Kurz] > > 2. Fix issue with error_abort & error_propagate: when we wrap > error_abort by local_err+error_propagate, resulting coredump will > refer to error_propagate and not to the place where error happened. I get what you mean, but I have plenty of context. > (the macro itself doesn't fix the issue, but it allows to [3.] drop all > local_err+error_propagate pattern, which will definitely fix the issue) The parenthesis is not part of the goal. > [Reported by Kevin Wolf] > > 3. Drop local_err+error_propagate pattern, which is used to workaround > void functions with errp parameter, when caller wants to know resulting > status. (Note: actually these functions could be merely updated to > return int error code). > > To achieve these goals, we need to add invocation of the macro at start > of functions, which needs error_prepend/error_append_hint (1.); add > invocation of the macro at start of functions which do > local_err+error_propagate scenario the check errors, drop local errors > from them and just use *errp instead (2., 3.). The paragraph talks about two cases: 1. and 2.+3. Makes me think we want two paragraphs, each illustrated with an example. What about you provide the examples, and then I try to polish the prose? > Signed-off-by: Vladimir Sementsov-Ogievskiy > Reviewed-by: Eric Blake > --- > > CC: Gerd Hoffmann > CC: "Gonglei (Arei)" > CC: Eduardo Habkost > CC: Igor Mammedov > CC: Laurent Vivier > CC: Amit Shah > CC: Kevin Wolf > CC: Max Reitz > CC: John Snow > CC: Ari Sundholm > CC: Pavel Dovgalyuk > CC: Paolo Bonzini > CC: Stefan Hajnoczi > CC: Fam Zheng > CC: Stefan Weil > CC: Ronnie Sahlberg > CC: Peter Lieven > CC: Eric Blake > CC: "Denis V. Lunev" > CC: Markus Armbruster > CC: Alberto Garcia > CC: Jason Dillaman > CC: Wen Congyang > CC: Xie Changlong > CC: Liu Yuan > CC: "Richard W.M. Jones" > CC: Jeff Cody > CC: "Marc-Andr=C3=A9 Lureau" > CC: "Daniel P. Berrang=C3=A9" > CC: Richard Henderson > CC: Greg Kurz > CC: "Michael S. Tsirkin" > CC: Marcel Apfelbaum > CC: Beniamino Galvani > CC: Peter Maydell > CC: "C=C3=A9dric Le Goater" > CC: Andrew Jeffery > CC: Joel Stanley > CC: Andrew Baumann > CC: "Philippe Mathieu-Daud=C3=A9" > CC: Antony Pavlov > CC: Jean-Christophe Dubois > CC: Peter Chubb > CC: Subbaraya Sundeep > CC: Eric Auger > CC: Alistair Francis > CC: "Edgar E. Iglesias" > CC: Stefano Stabellini > CC: Anthony Perard > CC: Paul Durrant > CC: Paul Burton > CC: Aleksandar Rikalo > CC: Chris Wulff > CC: Marek Vasut > CC: David Gibson > CC: Cornelia Huck > CC: Halil Pasic > CC: Christian Borntraeger > CC: "Herv=C3=A9 Poussineau" > CC: Xiao Guangrong > CC: Aurelien Jarno > CC: Aleksandar Markovic > CC: Mark Cave-Ayland > CC: Jason Wang > CC: Laszlo Ersek > CC: Yuval Shaia > CC: Palmer Dabbelt > CC: Sagar Karandikar > CC: Bastian Koppelmann > CC: David Hildenbrand > CC: Thomas Huth > CC: Eric Farman > CC: Matthew Rosato > CC: Hannes Reinecke > CC: Michael Walle > CC: Artyom Tarasenko > CC: Stefan Berger > CC: Samuel Thibault > CC: Alex Williamson > CC: Tony Krowiak > CC: Pierre Morel > CC: Michael Roth > CC: Hailiang Zhang > CC: Juan Quintela > CC: "Dr. David Alan Gilbert" > CC: Luigi Rizzo > CC: Giuseppe Lettieri > CC: Vincenzo Maffione > CC: Jan Kiszka > CC: Anthony Green > CC: Stafford Horne > CC: Guan Xuetao > CC: Max Filippov > CC: qemu-block@nongnu.org > CC: integration@gluster.org > CC: sheepdog@lists.wpkg.org > CC: qemu-arm@nongnu.org > CC: xen-devel@lists.xenproject.org > CC: qemu-ppc@nongnu.org > CC: qemu-s390x@nongnu.org > CC: qemu-riscv@nongnu.org > > include/qapi/error.h | 38 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 38 insertions(+) > > diff --git a/include/qapi/error.h b/include/qapi/error.h > index d6898d833b..47238d9065 100644 > --- a/include/qapi/error.h > +++ b/include/qapi/error.h > @@ -345,6 +345,44 @@ void error_set_internal(Error **errp, > ErrorClass err_class, const char *fmt, ...) > GCC_FMT_ATTR(6, 7); > =20 > +typedef struct ErrorPropagator { > + Error *local_err; > + Error **errp; > +} ErrorPropagator; > + > +static inline void error_propagator_cleanup(ErrorPropagator *prop) > +{ > + error_propagate(prop->errp, prop->local_err); > +} > + > +G_DEFINE_AUTO_CLEANUP_CLEAR_FUNC(ErrorPropagator, error_propagator_clean= up); > + > +/* > + * ERRP_AUTO_PROPAGATE > + * > + * This macro is created to be the first line of a function with Error *= *errp > + * OUT parameter. It's needed only in cases where we want to use error_p= repend, > + * error_append_hint or dereference *errp. It's still safe (but useless)= in > + * other cases. > + * > + * If errp is NULL or points to error_fatal, it is rewritten to point to= a > + * local Error object, which will be automatically propagated to the ori= ginal > + * errp on function exit (see error_propagator_cleanup). > + * > + * After invocation of this macro it is always safe to dereference errp > + * (as it's not NULL anymore) and to add information (by error_prepend o= r > + * error_append_hint) > + * (as, if it was error_fatal, we swapped it with a local_error to be > + * propagated on cleanup). > + * > + * Note: we don't wrap the error_abort case, as we want resulting coredu= mp > + * to point to the place where the error happened, not to error_propagat= e. > + */ > +#define ERRP_AUTO_PROPAGATE() \ > + g_auto(ErrorPropagator) _auto_errp_prop =3D {.errp =3D errp}; \ > + errp =3D ((errp =3D=3D NULL || *errp =3D=3D error_fatal) = \ > + ? &_auto_errp_prop.local_err : errp) > + > /* > * Special error destination to abort on error. > * See error_setg() and error_propagate() for details. Missing: update of the big comment starting with "Error reporting system loosely patterned after Glib's GError."