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=-6.3 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 26274C433DF for ; Fri, 29 May 2020 19:14:27 +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 E743920723 for ; Fri, 29 May 2020 19:14:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="fBzRthNa" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E743920723 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:36020 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jekSY-0002Lv-3m for qemu-devel@archiver.kernel.org; Fri, 29 May 2020 15:14:26 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59402) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jekRq-0001w7-H2 for qemu-devel@nongnu.org; Fri, 29 May 2020 15:13:42 -0400 Received: from mail-il1-x143.google.com ([2607:f8b0:4864:20::143]:44681) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jekRo-0001e0-UJ for qemu-devel@nongnu.org; Fri, 29 May 2020 15:13:42 -0400 Received: by mail-il1-x143.google.com with SMTP id j3so3527350ilk.11 for ; Fri, 29 May 2020 12:13:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=18PMaFGqx3ZQQaSbzUFmorqZGVmmD38umv1uirOCgAE=; b=fBzRthNa2BvKUu6iAfW9BY+ICOzqC8dlooQyAElhYnsJV4V4wbQfAQ+3VGvFuCD5Hd +wt+UmwGcJyLu2xHG0UFT2YneoECKirfMc8dy6gSRhqhX2A+63vge3u7MpdmF+nhR3zQ rV8W7qXHbL6fRzFZpkY2rPgV2PqBRAoDM1K2Bdrna35Qtr0uNNxrc66EWuDnmuwpnFuj I3lG7yzUbcoE5Fs62tju/vGpFxOZ80ihN3gsp1cV82GGadWDKKnlg5ZrYdtpBjk/yHmA GVd63uMBasscPFhN4wuxTAatVOTKRR3Mjzov0c0AJtMg4AOKEA7Onk83yRqtArqlc7V2 MdtQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=18PMaFGqx3ZQQaSbzUFmorqZGVmmD38umv1uirOCgAE=; b=abAbcQmoXJg+FBU4aLdCmICYXrMkHlovVtDRlTRSPs8uOxdTqY3k6raS8ThkXG0RC+ wBhHznmT9RFCQIhNvlyCf2xCHF83IA8CqNSdVNex80+A+P9AvIr6n5ONXfCDqIRLvF00 KcwlaxU9r1ykVicAfVODh96liIxZ/ZXpLks1Nm/zP6hX9gHQxvZiod/hXfx7IOotT00o scizb5BWtfHu2d8xnH4klhtp0GYsgp9XVh5DY5SpQiMi2EZfCIvOGVNs8RR9tKx+QhMh t6q/tYTl8uLMoaZ39Hsss/I/hAMko2Bxw1QYmAVU8CGw6CXhIAb2lcw4XOkKLAoY1BD9 EXEw== X-Gm-Message-State: AOAM530gSkmyxARGplB49cEULUfzJ7vUIRuVZm/HkgBBjixb6SgoNJhS F9QP1LwYlA5JCSIXDNQrgDcXVNzRXXrSssyrPmo= X-Google-Smtp-Source: ABdhPJxvLnpELtDZ/pkjQheofdjvo0ZIC0bcY23F5Q7u45WEIPfRVlQyU5WNXuLlijcfLgvpPs5ZqRyHaDLu/vZJG98= X-Received: by 2002:a92:aa07:: with SMTP id j7mr9148059ili.40.1590779618528; Fri, 29 May 2020 12:13:38 -0700 (PDT) MIME-Version: 1.0 References: <20200529134523.8477-1-armbru@redhat.com> <20200529134523.8477-5-armbru@redhat.com> In-Reply-To: <20200529134523.8477-5-armbru@redhat.com> From: Alistair Francis Date: Fri, 29 May 2020 12:04:35 -0700 Message-ID: Subject: Re: [PATCH v2 04/58] qdev: New qdev_new(), qdev_realize(), etc. To: Markus Armbruster Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2607:f8b0:4864:20::143; envelope-from=alistair23@gmail.com; helo=mail-il1-x143.google.com X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Spam_score_int: -17 X-Spam_score: -1.8 X-Spam_bar: - X-Spam_report: (-1.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN 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: "Michael S . Tsirkin" , Alistair Francis , Mark Cave-Ayland , "qemu-devel@nongnu.org Developers" , Gerd Hoffmann , David Gibson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, May 29, 2020 at 7:03 AM Markus Armbruster wrote: > > We commonly plug devices into their bus right when we create them, > like this: > > dev = qdev_create(bus, type_name); > > Note that @dev is a weak reference. The reference from @bus to @dev > is the only strong one. > > We realize at some later time, either with > > object_property_set_bool(OBJECT(dev), true, "realized", errp); > > or its convenience wrapper > > qdev_init_nofail(dev); > > If @dev still has no QOM parent then, realizing makes the > /machine/unattached/ orphanage its QOM parent. > > Note that the device returned by qdev_create() is plugged into a bus, > but doesn't have a QOM parent, yet. Until it acquires one, > unrealizing the bus will hang in bus_unparent(): > > while ((kid = QTAILQ_FIRST(&bus->children)) != NULL) { > DeviceState *dev = kid->child; > object_unparent(OBJECT(dev)); > } > > object_unparent() does nothing when its argument has no QOM parent, > and the loop spins forever. > > Device state "no QOM parent, but plugged into bus" is dangerous. > > Paolo suggested to delay plugging into the bus until realize. We need > to plug into the parent bus before we call the device's realize > method, in case it uses the parent bus. So the dangerous state still > exists, but only within realization, where we can manage it safely. > > This commit creates infrastructure to do this: > > dev = qdev_new(type_name); > ... > qdev_realize_and_unref(dev, bus, errp) > > Note that @dev becomes a strong reference here. > qdev_realize_and_unref() drops it. There is also plain > qdev_realize(), which doesn't drop it. > > The remainder of this series will convert all users to this new > interface. > > Cc: Michael S. Tsirkin > Cc: Marcel Apfelbaum > Cc: Alistair Francis > Cc: Gerd Hoffmann > Cc: Mark Cave-Ayland > Cc: David Gibson > Signed-off-by: Markus Armbruster > Acked-by: Gerd Hoffmann Reviewed-by: Alistair Francis Alistair > --- > include/hw/qdev-core.h | 11 +++++- > hw/core/bus.c | 14 +++++++ > hw/core/qdev.c | 90 ++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 114 insertions(+), 1 deletion(-) > > diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h > index b870b27966..fba29308f7 100644 > --- a/include/hw/qdev-core.h > +++ b/include/hw/qdev-core.h > @@ -57,7 +57,7 @@ typedef void (*BusUnrealize)(BusState *bus); > * After successful realization, setting static properties will fail. > * > * As an interim step, the #DeviceState:realized property can also be > - * set with qdev_init_nofail(). > + * set with qdev_realize() or qdev_init_nofail(). > * In the future, devices will propagate this state change to their children > * and along busses they expose. > * The point in time will be deferred to machine creation, so that values > @@ -322,7 +322,13 @@ compat_props_add(GPtrArray *arr, > > DeviceState *qdev_create(BusState *bus, const char *name); > DeviceState *qdev_try_create(BusState *bus, const char *name); > +DeviceState *qdev_new(const char *name); > +DeviceState *qdev_try_new(const char *name); > void qdev_init_nofail(DeviceState *dev); > +bool qdev_realize(DeviceState *dev, BusState *bus, Error **errp); > +bool qdev_realize_and_unref(DeviceState *dev, BusState *bus, Error **errp); > +void qdev_unrealize(DeviceState *dev); > + > void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id, > int required_for_version); > HotplugHandler *qdev_get_bus_hotplug_handler(DeviceState *dev); > @@ -411,6 +417,9 @@ typedef int (qdev_walkerfn)(DeviceState *dev, void *opaque); > void qbus_create_inplace(void *bus, size_t size, const char *typename, > DeviceState *parent, const char *name); > BusState *qbus_create(const char *typename, DeviceState *parent, const char *name); > +bool qbus_realize(BusState *bus, Error **errp); > +void qbus_unrealize(BusState *bus); > + > /* Returns > 0 if either devfn or busfn skip walk somewhere in cursion, > * < 0 if either devfn or busfn terminate walk somewhere in cursion, > * 0 otherwise. */ > diff --git a/hw/core/bus.c b/hw/core/bus.c > index 33a4443217..6f6071f5fa 100644 > --- a/hw/core/bus.c > +++ b/hw/core/bus.c > @@ -164,6 +164,20 @@ BusState *qbus_create(const char *typename, DeviceState *parent, const char *nam > return bus; > } > > +bool qbus_realize(BusState *bus, Error **errp) > +{ > + Error *err = NULL; > + > + object_property_set_bool(OBJECT(bus), true, "realized", &err); > + error_propagate(errp, err); > + return !err; > +} > + > +void qbus_unrealize(BusState *bus) > +{ > + object_property_set_bool(OBJECT(bus), false, "realized", &error_abort); > +} > + > static bool bus_get_realized(Object *obj, Error **errp) > { > BusState *bus = BUS(obj); > diff --git a/hw/core/qdev.c b/hw/core/qdev.c > index a68ba674db..f2c5cee278 100644 > --- a/hw/core/qdev.c > +++ b/hw/core/qdev.c > @@ -176,6 +176,32 @@ DeviceState *qdev_try_create(BusState *bus, const char *type) > return dev; > } > > +/* > + * Create a device on the heap. > + * A type @name must exist. > + * This only initializes the device state structure and allows > + * properties to be set. The device still needs to be realized. See > + * qdev-core.h. > + */ > +DeviceState *qdev_new(const char *name) > +{ > + return DEVICE(object_new(name)); > +} > + > +/* > + * Try to create a device on the heap. > + * This is like qdev_new(), except it returns %NULL when type @name > + * does not exist. > + */ > +DeviceState *qdev_try_new(const char *name) > +{ > + if (!object_class_by_name(name)) { > + return NULL; > + } > + > + return DEVICE(object_new(name)); > +} > + > static QTAILQ_HEAD(, DeviceListener) device_listeners > = QTAILQ_HEAD_INITIALIZER(device_listeners); > > @@ -427,6 +453,66 @@ void qdev_init_nofail(DeviceState *dev) > object_unref(OBJECT(dev)); > } > > +/* > + * Realize @dev. > + * @dev must not be plugged into a bus. > + * Plug @dev into @bus if non-null, else into the main system bus. > + * This takes a reference to @dev. > + * If @dev has no QOM parent, make one up, taking another reference. > + * On success, return true. > + * On failure, store an error through @errp and return false. > + */ > +bool qdev_realize(DeviceState *dev, BusState *bus, Error **errp) > +{ > + Error *err = NULL; > + > + assert(!dev->realized && !dev->parent_bus); > + > + if (!bus) { > + /* > + * Assert that the device really is a SysBusDevice before we > + * put it onto the sysbus. Non-sysbus devices which aren't > + * being put onto a bus should be realized with > + * object_property_set_bool(OBJECT(dev), true, "realized", > + * errp); > + */ > + g_assert(object_dynamic_cast(OBJECT(dev), TYPE_SYS_BUS_DEVICE)); > + bus = sysbus_get_default(); > + } > + > + qdev_set_parent_bus(dev, bus); > + > + object_property_set_bool(OBJECT(dev), true, "realized", &err); > + if (err) { > + error_propagate(errp, err); > + } > + return !err; > +} > + > +/* > + * Realize @dev and drop a reference. > + * This is like qdev_realize(), except the caller must hold a > + * (private) reference, which is dropped on return regardless of > + * success or failure. Intended use: > + * dev = qdev_new(); > + * [...] > + * qdev_realize_and_unref(dev, bus, errp); > + * Now @dev can go away without further ado. > + */ > +bool qdev_realize_and_unref(DeviceState *dev, BusState *bus, Error **errp) > +{ > + bool ret; > + > + ret = qdev_realize(dev, bus, errp); > + object_unref(OBJECT(dev)); > + return ret; > +} > + > +void qdev_unrealize(DeviceState *dev) > +{ > + object_property_set_bool(OBJECT(dev), false, "realized", &error_abort); > +} > + > static int qdev_assert_realized_properly(Object *obj, void *opaque) > { > DeviceState *dev = DEVICE(object_dynamic_cast(obj, TYPE_DEVICE)); > @@ -1002,6 +1088,10 @@ post_realize_fail: > fail: > error_propagate(errp, local_err); > if (unattached_parent) { > + /* > + * Beware, this doesn't just revert > + * object_property_add_child(), it also runs bus_remove()! > + */ > object_unparent(OBJECT(dev)); > unattached_count--; > } > -- > 2.21.3 > >