From: Paolo Bonzini <pbonzini@redhat.com>
To: Markus Armbruster <armbru@redhat.com>
Cc: berrange@redhat.com, qemu-devel@nongnu.org, ehabkost@redhat.com
Subject: Re: [PATCH 51/55] qdev: Make qdev_realize() support bus-less devices
Date: Wed, 20 May 2020 18:24:01 +0200 [thread overview]
Message-ID: <1b43c6cb-ac47-1fcb-72b4-e96ae00141b1@redhat.com> (raw)
In-Reply-To: <87lflmps2w.fsf@dusky.pond.sub.org>
On 20/05/20 17:02, Markus Armbruster wrote:
>>>
>>> qdev_realize_and_unref() remains restricted, because its reference
>>> counting would become rather confusing for bus-less devices.
>> I think it would be fine, you would just rely on the reference held by
>> the QOM parent (via the child property).
> I took one look at the contract I wrote for it, and balked :)
>
> qdev_realize()'s contract before this patch:
>
> /*
> * Realize @dev.
> * @dev must not be plugged into a bus.
> * Plug @dev into @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)
>
> Simple enough.
>
> This patch merely adds "If @bus, " before "plug". Still simple enough.
>
> qdev_realize_and_unref()'s contract:
>
> /*
> * Realize @dev and drop a reference.
> * This is like qdev_realize(), except it steals a reference rather
> * than take one to plug @dev into @bus. On failure, it drops that
> * reference instead. @bus must not be null. 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)
>
> If @bus is null, who gets to hold the stolen reference?
>
> You seem to suggest the QOM parent. What if @dev already has a parent?
The caller would still hold the stolen reference, and it would be
dropped. You cannot have a device that goes away at the end of
qdev_realize_and_unref, as long as dev has a QOM parent that clings onto
dev. Since dev will have /machine/unattached as the parent if it didn't
already have one before, the function is safe even without a bus.
Or alternatively, ignore all the stolen references stuff, and merely see
qdev_realize_and_unref as a shortcut for qdev_realize+object_unref,
because it's a common idiom.
Paolo
next prev parent reply other threads:[~2020-05-20 16:25 UTC|newest]
Thread overview: 125+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-19 14:54 [PATCH 00/55] qdev: Rework how we plug into the parent bus Markus Armbruster
2020-05-19 14:54 ` [PATCH 01/55] qdev: Rename qbus_realize() to qbus_init() Markus Armbruster
2020-05-19 14:54 ` [PATCH 02/55] qdev: Drop redundant bus realization Markus Armbruster
2020-05-20 12:00 ` Philippe Mathieu-Daudé
2020-05-20 14:25 ` Markus Armbruster
2020-05-19 14:54 ` [PATCH 03/55] qdev: New qdev_new(), qdev_realize(), etc Markus Armbruster
2020-05-19 21:02 ` Alistair Francis
2020-05-20 4:26 ` Markus Armbruster
2020-05-20 4:51 ` Alistair Francis
2020-05-20 7:29 ` Markus Armbruster
2020-05-20 6:22 ` Paolo Bonzini
2020-05-20 8:11 ` Markus Armbruster
2020-05-20 8:17 ` Paolo Bonzini
2020-05-20 14:42 ` Markus Armbruster
2020-05-20 16:28 ` Paolo Bonzini
2020-05-25 6:30 ` Markus Armbruster
2020-05-25 6:40 ` Paolo Bonzini
2020-05-29 12:22 ` Markus Armbruster
2020-05-20 8:49 ` Gerd Hoffmann
2020-05-19 14:55 ` [PATCH 04/55] qdev: Put qdev_new() to use with Coccinelle Markus Armbruster
2020-05-19 14:55 ` [PATCH 05/55] qdev: Convert to qbus_realize(), qbus_unrealize() Markus Armbruster
2020-05-19 14:55 ` [PATCH 06/55] qdev: Convert to qdev_unrealize() with Coccinelle Markus Armbruster
2020-05-19 14:55 ` [PATCH 07/55] qdev: Convert to qdev_unrealize() manually Markus Armbruster
2020-05-20 6:25 ` Paolo Bonzini
2020-05-20 8:12 ` Markus Armbruster
2020-05-19 14:55 ` [PATCH 08/55] qdev: Convert uses of qdev_create() with Coccinelle Markus Armbruster
2020-05-20 6:30 ` Paolo Bonzini
2020-05-20 8:16 ` Markus Armbruster
2020-05-19 14:55 ` [PATCH 09/55] qdev: Convert uses of qdev_create() manually Markus Armbruster
2020-05-19 14:55 ` [PATCH 10/55] qdev: Convert uses of qdev_set_parent_bus() with Coccinelle Markus Armbruster
2020-05-19 14:55 ` [PATCH 11/55] qdev: Convert uses of qdev_set_parent_bus() manually Markus Armbruster
2020-05-19 14:55 ` [PATCH 12/55] pci: New pci_new(), pci_realize_and_unref() etc Markus Armbruster
2020-05-19 14:55 ` [PATCH 13/55] hw/ppc: Eliminate two superfluous QOM casts Markus Armbruster
2020-05-26 11:56 ` Philippe Mathieu-Daudé
2020-05-19 14:55 ` [PATCH 14/55] pci: Convert uses of pci_create() etc. with Coccinelle Markus Armbruster
2020-05-19 14:55 ` [PATCH 15/55] pci: Convert uses of pci_create() etc. manually Markus Armbruster
2020-05-19 14:55 ` [PATCH 16/55] pci: pci_create(), pci_create_multifunction() are now unused, drop Markus Armbruster
2020-05-19 14:55 ` [PATCH 17/55] isa: New isa_new(), isa_realize_and_unref() etc Markus Armbruster
2020-05-19 14:55 ` [PATCH 18/55] isa: Convert uses of isa_create() with Coccinelle Markus Armbruster
2020-05-19 14:55 ` [PATCH 19/55] isa: Convert uses of isa_create(), isa_try_create() manually Markus Armbruster
2020-05-19 14:55 ` [PATCH 20/55] isa: isa_create(), isa_try_create() are now unused, drop Markus Armbruster
2020-05-19 14:55 ` [PATCH 21/55] ssi: ssi_auto_connect_slaves() never does anything, drop Markus Armbruster
2020-05-19 21:08 ` Alistair Francis
2020-05-19 14:55 ` [PATCH 22/55] ssi: Convert uses of ssi_create_slave_no_init() with Coccinelle Markus Armbruster
2020-05-19 21:07 ` Alistair Francis
2020-05-19 14:55 ` [PATCH 23/55] ssi: Convert last use of ssi_create_slave_no_init() manually Markus Armbruster
2020-05-19 20:58 ` Alistair Francis
2020-05-19 14:55 ` [PATCH 24/55] ssi: ssi_create_slave_no_init() is now unused, drop Markus Armbruster
2020-05-19 21:11 ` Alistair Francis
2020-05-19 14:55 ` [PATCH 25/55] usb: New usb_new(), usb_realize_and_unref() Markus Armbruster
2020-05-20 8:44 ` Gerd Hoffmann
2020-05-19 14:55 ` [PATCH 26/55] usb: Convert uses of usb_create() Markus Armbruster
2020-05-20 8:45 ` Gerd Hoffmann
2020-05-19 14:55 ` [PATCH 27/55] usb: usb_create() is now unused, drop Markus Armbruster
2020-05-20 8:46 ` Gerd Hoffmann
2020-05-19 14:55 ` [PATCH 28/55] usb: Eliminate usb_try_create_simple() Markus Armbruster
2020-05-20 8:46 ` Gerd Hoffmann
2020-05-19 14:55 ` [PATCH 29/55] qdev: qdev_create(), qdev_try_create() are now unused, drop Markus Armbruster
2020-05-19 14:55 ` [PATCH 30/55] auxbus: New aux_realize_bus(), pairing with aux_init_bus() Markus Armbruster
2020-05-26 11:54 ` Philippe Mathieu-Daudé
2020-05-27 4:39 ` Markus Armbruster
2020-05-19 14:55 ` [PATCH 31/55] auxbus: Convert a use of qdev_set_parent_bus() Markus Armbruster
2020-05-19 14:55 ` [PATCH 32/55] auxbus: Eliminate aux_create_slave() Markus Armbruster
2020-05-20 11:52 ` Philippe Mathieu-Daudé
2020-05-19 14:55 ` [PATCH 33/55] qom: Tidy up a few object_initialize_child() calls Markus Armbruster
2020-05-19 21:14 ` Alistair Francis
2020-05-26 11:51 ` Philippe Mathieu-Daudé
2020-05-19 14:55 ` [PATCH 34/55] qom: Less verbose object_initialize_child() Markus Armbruster
2020-05-19 21:16 ` Alistair Francis
2020-05-19 14:55 ` [PATCH 35/55] macio: Convert use of qdev_set_parent_bus() Markus Armbruster
2020-05-19 14:55 ` [PATCH 36/55] macio: Eliminate macio_init_child_obj() Markus Armbruster
2020-05-19 14:55 ` [PATCH 37/55] sysbus: Drop useless OBJECT() in sysbus_init_child_obj() calls Markus Armbruster
2020-05-20 12:02 ` Philippe Mathieu-Daudé
2020-05-19 14:55 ` [PATCH 38/55] microbit: Tidy up sysbus_init_child_obj() @child argument Markus Armbruster
2020-05-20 12:06 ` Philippe Mathieu-Daudé
2020-05-20 14:49 ` Markus Armbruster
2020-05-20 14:54 ` Philippe Mathieu-Daudé
2020-05-19 14:55 ` [PATCH 39/55] sysbus: Tidy up sysbus_init_child_obj()'s @childsize arg, part 1 Markus Armbruster
2020-05-19 14:55 ` [PATCH 40/55] hw/arm/armsse: Pass correct child size to sysbus_init_child_obj() Markus Armbruster
2020-05-20 11:51 ` Philippe Mathieu-Daudé
2020-05-20 14:54 ` Markus Armbruster
2020-05-19 14:55 ` [PATCH 41/55] sysbus: Tidy up sysbus_init_child_obj()'s @childsize arg, part 2 Markus Armbruster
2020-05-19 14:55 ` [PATCH 42/55] sysbus: New sysbus_realize(), sysbus_realize_and_unref() Markus Armbruster
2020-05-19 14:55 ` [PATCH 43/55] sysbus: Convert to sysbus_realize() etc. with Coccinelle Markus Armbruster
2020-05-19 21:18 ` Alistair Francis
2020-05-19 14:55 ` [PATCH 44/55] qdev: Drop qdev_realize() support for null bus Markus Armbruster
2020-05-19 14:55 ` [PATCH 45/55] sysbus: Convert qdev_set_parent_bus() use with Coccinelle, part 1 Markus Armbruster
2020-05-19 21:25 ` Alistair Francis
2020-05-19 14:55 ` [PATCH 46/55] sysbus: Convert qdev_set_parent_bus() use with Coccinelle, part 2 Markus Armbruster
2020-05-19 21:26 ` Alistair Francis
2020-05-19 14:55 ` [PATCH 47/55] sysbus: Convert qdev_set_parent_bus() use with Coccinelle, part 3 Markus Armbruster
2020-05-19 14:55 ` [PATCH 48/55] sysbus: Convert qdev_set_parent_bus() use with Coccinelle, part 4 Markus Armbruster
2020-05-19 14:55 ` [PATCH 49/55] sysbus: sysbus_init_child_obj() is now unused, drop Markus Armbruster
2020-05-19 14:55 ` [PATCH 50/55] s390x/event-facility: Simplify creation of SCLP event devices Markus Armbruster
2020-05-20 8:09 ` David Hildenbrand
2020-05-21 8:44 ` David Hildenbrand
2020-05-25 7:01 ` Markus Armbruster
2020-05-25 8:26 ` Paolo Bonzini
2020-05-26 6:27 ` Markus Armbruster
2020-05-26 7:51 ` Paolo Bonzini
2020-05-26 8:59 ` Markus Armbruster
2020-05-29 13:45 ` Markus Armbruster
2020-05-26 9:45 ` Cornelia Huck
2020-05-26 11:23 ` Paolo Bonzini
2020-05-26 11:38 ` Cornelia Huck
2020-05-26 9:59 ` David Hildenbrand
2020-05-19 14:55 ` [PATCH 51/55] qdev: Make qdev_realize() support bus-less devices Markus Armbruster
2020-05-20 6:43 ` Paolo Bonzini
2020-05-20 15:02 ` Markus Armbruster
2020-05-20 16:24 ` Paolo Bonzini [this message]
2020-05-25 6:38 ` Markus Armbruster
2020-05-25 10:11 ` Paolo Bonzini
2020-05-26 5:14 ` Markus Armbruster
2020-05-26 7:54 ` Paolo Bonzini
2020-05-19 14:55 ` [PATCH 52/55] qdev: Use qdev_realize() in qdev_device_add() Markus Armbruster
2020-05-19 14:55 ` [PATCH 53/55] qdev: Convert bus-less devices to qdev_realize() with Coccinelle Markus Armbruster
2020-05-19 21:28 ` Alistair Francis
2020-05-19 14:55 ` [PATCH 54/55] qdev: qdev_init_nofail() is now unused, drop Markus Armbruster
2020-05-19 14:55 ` [PATCH 55/55] MAINTAINERS: Make section QOM cover hw/core/*bus.c as well Markus Armbruster
2020-05-20 6:46 ` [PATCH 00/55] qdev: Rework how we plug into the parent bus Paolo Bonzini
2020-06-08 10:56 ` Markus Armbruster
2020-06-08 10:59 ` Paolo Bonzini
2020-06-09 6:41 ` Markus Armbruster
2020-06-09 6:55 ` Paolo Bonzini
2020-06-09 9:34 ` Markus Armbruster
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