linux-kernel - Re: [PATCH] driver core: fix possible missing of device probe

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Message-ID: <CACVXFVPZYiNvBf1ongckAcsikG4FxrRrJ9C4Uye5+6qxP4jwBQ@mail.gmail.com>
Date:	Fri, 28 Sep 2012 22:22:06 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	anish singh <anish198519851985@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] driver core: fix possible missing of device probe

On Fri, Sep 28, 2012 at 10:13 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Fri, Sep 28, 2012 at 10:07:22PM +0800, Ming Lei wrote:
>> On Fri, Sep 28, 2012 at 9:55 PM, Russell King - ARM Linux
>> <linux@....linux.org.uk> wrote:
>> >> I do not mention threads case in one CPU because the context in
>> >> which device_add runs will always see the driver added into
>> >
>> > There you go again.  Look at my _much_ better description of the problem
>> > and you'll notice that device_add has nothing to do with this.
>>
>> OK, I explain it again:
>>
>> CPU0                                          CPU1
>>
>> driver_register
>>       ...
>>       bus_add_driver
>>               driver_attach
>>                                               device_add(devb)
>>
>>               klist_add_tail(klist_drivers)
>>
>> When device_add(devb) is run just after completion of driver_attach
>> and before klist_add_tail(klist_drivers), the 'devb' can't be probed
>> in device_add because the driver hasn't been added into bus,
>> and it wasn't be probed in driver_attach because driver_attach didn't
>> see the device in the bus.
>>
>> So the 'devb' will be missed to be probed in the bus, won't it?
>
> Wait a moment.  You're describing a *totally* *different* problem to
> the problem I reported.  I say - for the third time - that in the

I don't see there is any difference between them. In my above description,
it will become same if the 'device_add' is changed to 'bus_probe_device'.

I have mentioned it in my commit log already.

> problem I reported, device_add() has NOTHING TO DO WITH IT.
>
> In your previous mail, you complained that my description did not
> cover another case.  I throw that back at you and say to you that
> _your_ description does _not_ cover my case, but refers to a
> _different_ problem which happens to be fixed by the _same_ fix.

As said above, if 'device_add()' is replaced with 'bus_probe_device()',
that becomes your problem, right?

>
> To attach my "reported-by" to a problem description which is not
> the problem that I reported is bad practice, and actually creates
> a lie.  If you wish to keep your problem description, then you must
> remove my Reported-by, because the problem you refer to in your
> description is not _my_ problem.

I mentioned 'bus_probe_device'  case in my commit log.
If you still think that is not your problem, I can remove the reported-by.


Thanks,
--
Ming Lei
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