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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 F1ACEC433B4 for ; Wed, 12 May 2021 15:48:56 +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 62A2F619B6 for ; Wed, 12 May 2021 15:48:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 62A2F619B6 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]:59560 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lgr6V-0000cb-Ba for qemu-devel@archiver.kernel.org; Wed, 12 May 2021 11:48:55 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52568) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lgr2y-0006ew-B7 for qemu-devel@nongnu.org; Wed, 12 May 2021 11:45:16 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:50545) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lgr2o-0000Oy-DC for qemu-devel@nongnu.org; Wed, 12 May 2021 11:45:11 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620834305; 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: in-reply-to:in-reply-to:references:references; bh=6fryYKZjBUvcsY+wdKjK32hFu/Xz/bMDYgYD+szHsEI=; b=Xq8ZhZ0VfXQBqo+ACU/JOqSjAglt1nzzWoOr2ScPOmaZP2VTyOmEcBeherJGIRq+Jw7a/I 5OXvFbENE1N4Lo3b/y0YY0WfobYneQnGAeQkMT1UAwEJZrYhxrx/WzSWEwdupL1zH0WoGm wg1rQnlYtmZzqT0Ny9LqV7y+lVFshR0= 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-14-skhcaHp7NTSQDbKoJSl8Bg-1; Wed, 12 May 2021 11:45:03 -0400 X-MC-Unique: skhcaHp7NTSQDbKoJSl8Bg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B7B5E1009465; Wed, 12 May 2021 15:45:01 +0000 (UTC) Received: from localhost (ovpn-115-51.ams2.redhat.com [10.36.115.51]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3630C5D6AC; Wed, 12 May 2021 15:45:01 +0000 (UTC) Date: Wed, 12 May 2021 16:44:59 +0100 From: Stefan Hajnoczi To: Emanuele Giuseppe Esposito Subject: Re: [PATCH 5/6] co-shared-resource: protect with a mutex Message-ID: References: <20210510085941.22769-1-eesposit@redhat.com> <20210510085941.22769-6-eesposit@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210510085941.22769-6-eesposit@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="nJNVInJjSJRN/GUy" Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.7, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: Kevin Wolf , Vladimir Sementsov-Ogievskiy , qemu-block@nongnu.org, qemu-devel@nongnu.org, Max Reitz , Paolo Bonzini , John Snow Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --nJNVInJjSJRN/GUy Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, May 10, 2021 at 10:59:40AM +0200, Emanuele Giuseppe Esposito wrote: > co-shared-resource is currently not thread-safe, as also reported > in co-shared-resource.h. Add a QemuMutex because co_try_get_from_shres > can also be invoked from non-coroutine context. >=20 > Signed-off-by: Emanuele Giuseppe Esposito > --- > util/qemu-co-shared-resource.c | 26 ++++++++++++++++++++++---- > 1 file changed, 22 insertions(+), 4 deletions(-) Hmm...this thread-safety change is more fine-grained than I was expecting. If we follow this strategy basically any data structure used by coroutines needs its own fine-grained lock (like Java's Object base class which has its own lock). I'm not sure I like it since callers may still need coarser grained locks to protect their own state or synchronize access to multiple items of data. Also, some callers may not need thread-safety. Can the caller to be responsible for locking instead (e.g. using CoMutex)? > diff --git a/util/qemu-co-shared-resource.c b/util/qemu-co-shared-resourc= e.c > index 1c83cd9d29..c455d02a1e 100644 > --- a/util/qemu-co-shared-resource.c > +++ b/util/qemu-co-shared-resource.c > @@ -32,6 +32,7 @@ struct SharedResource { > uint64_t available; > =20 > CoQueue queue; > + QemuMutex lock; Please add a comment indicating what this lock protects. Thread safety should also be documented in the header file so API users know what to expect. --nJNVInJjSJRN/GUy Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmCb9/sACgkQnKSrs4Gr c8gGcQf/XvW6glaozb9KFXyMRFwDfO4IOgfJMBsmAZh7vW1rNl+Up0fbEOQ7CjRA arzSvhwyuBrNjZimZoo8mnqiydh0po5vWDPeRcbjBPZqI1Vf3luNiYfhVlSzPXxd YuF6jyJh/ODTYWHqw/xwMGJub240esP4cURRsaZP28w/qskTJH8wYwb2Re65XbKs Cb5a3yJztSqwmUqwZ+jiEk7EM8OAAI9yyTBUkUi0NlWBoaq+XUxDvF+3Fy8Us1jU c1dbvnrmpKcgs7EKw/W3wO/vFH9dQNCvrxUjeO8UDesHN7wYTuHtZiRZKy9a0szt 1l0eT88xPP8TNDZEX1qbS1ciQUYvIg== =2z6+ -----END PGP SIGNATURE----- --nJNVInJjSJRN/GUy--