Re: [Qemu-devel] [PATCH v2] qdev: Keep global allocation counter per bus

[Andreas Färber]

Am 08.01.2014 09:13, schrieb Markus Armbruster:
> Peter Crosthwaite <address@hidden> writes:
> 
>> On Wed, Jan 8, 2014 at 2:59 AM, Paolo Bonzini <address@hidden> wrote:
>>> Il 07/01/2014 16:12, Markus Armbruster ha scritto:
>>>>     aarch64     akita           info qtree crashes
>>>>     aarch64     borzoi          info qtree crashes
>>>>     aarch64     spitz           info qtree crashes
>>>>     aarch64     terrier         info qtree crashes
>>>>     aarch64     tosa            info qtree crashes
>>>>     arm         akita           info qtree crashes
>>>>     arm         borzoi          info qtree crashes
>>>>     arm         spitz           info qtree crashes
>>>>     arm         terrier         info qtree crashes
>>>>     arm         tosa            info qtree crashes
>>>>     cris        axis-dev88      info qtree crashes
>>>
>>> The crash is because of commit 7426aa7 (nand: Don't inherit from Sysbus,
>>> 2013-06-18).   Should probably be reverted.
>>>
>>
>> Prefer not, under no reasonable definition is NAND a sysbus device.
>> Whats the real problem here? What is TYPE_SYS_BUS_DEVICE doing WRT to
>> qtree that TYPE_DEVICE is not?
> 
> Maybe, but our definition of sysbus has never been reasonable :)
> 
> Qdev, as designed by Paul Brook, assumed the parent of a qdev is always
> a qbus and vice versa.  With the exception of the root, which has no
> parent, and is a sysbus, commonly the only one.
> 
> A PCI qdev plugs into a PCI qbus, an USB qdev plugs into an USB qbus,
> and so forth.  Any qdev that doesn't really plug into a bus was made a
> "sysbus device" by fiat.  "Sysbus" is a catchall, no more.  In
> particular, it's not a bus in the hardware sense.
> 
> This "everything plugs into exactly one bus" assumption is of course a
> gross oversimplification, and we've been working on overcoming it for
> quite some time.  It has become possible to define qdevs that aren't
> connected to a qbus.  A TYPE_DEVICE isn't.
> 
> That's progress.  But progress isn't justification for not fixing crash
> bugs in monitor commands.
> 
> Either you fix "info qtree" to cope with your change to the device
> graph, or the change needs to be reverted until somebody fixes it or it
> goes away.

Sharing a backtrace would be a start, rather than just throwing around
the word "crash" to justify reverting patches. :)

Andreas

-- 
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg