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: Tue, 26 May 2020 09:54:31 +0200 [thread overview]
Message-ID: <11771963-13dc-704b-d412-9853c81d7555@redhat.com> (raw)
In-Reply-To: <87y2pf9t19.fsf@dusky.pond.sub.org>
On 26/05/20 07:14, Markus Armbruster wrote:
>>> The contract must specify exactly what happens to the reference count,
>>> case by case.
>>
>> For both qdev_realize and qdev_realize_and_unref, on return the caller
>> need not care about keeping alive the device in the long-term.
>>
>> For qdev_realize_and_unref, the caller must _also_ have a "private"
>> reference to the object, which will be dropped on return.
>>
>> For qdev_realize, the caller _can_ have a private reference that it has
>> to later drop at a convenient time, but it could also ensure that the
>> device has a long-term reference via object->parent instead.
>
> I need a contract. The difficulty of writing a clear contract, caused
> by a case that doesn't actually occur, is what made me limit null bus to
> qdev_realize(). I admittedly didn't try hard. Next try:
>
> /*
> * 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.
> */
Works for me!
>> Perhaps this tells us that the /machine/unattached automation actually
>> shouldn't be moved to qdev_realize, but rather to
>> qdev_realize_and_unref, and qdev_realize could assert that there is a
>> parent already at the time of the call. However it is probably too
>> early to make a decision on that.
>
> The common pairings are qdev_new() with qdev_realize_and_unref(), and
> object_initialize_child() with qdev_realize(). Your idea obviously
> works for these. Whether there are other uses where it might not work,
> I can't say offhand.
Yes, let's look at it after this is committed. But I think it is at
least sensible, in the long term, for the *_new variants or their
callers to all take care of adding the child, and then
qdev_realize_and_unref() can go away.
Paolo
Paolo
next prev parent reply other threads:[~2020-05-26 7:55 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
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 [this message]
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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