linux-kernel - Re: [PATCH v2 2/2] of: __of_detach_node()

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Date:   Tue, 18 Dec 2018 12:33:18 -0800
From:   Frank Rowand <frowand.list@...il.com>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Michael Ellerman <mpe@...erman.id.au>, mwb@...ux.vnet.ibm.com,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Tyrel Datwyler <tyreld@...ux.vnet.ibm.com>,
        tlfalcon@...ux.vnet.ibm.com, minkim@...ibm.com,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] of: __of_detach_node() - remove node from phandle
 cache

On 12/18/18 12:09 PM, Frank Rowand wrote:
> On 12/18/18 12:01 PM, Rob Herring wrote:
>> On Tue, Dec 18, 2018 at 12:57 PM Frank Rowand <frowand.list@...il.com> wrote:
>>>
>>> On 12/17/18 2:52 AM, Michael Ellerman wrote:
>>>> Hi Frank,
>>>>
>>>> frowand.list@...il.com writes:
>>>>> From: Frank Rowand <frank.rowand@...y.com>
>>>>>
>>>>> Non-overlay dynamic devicetree node removal may leave the node in
>>>>> the phandle cache.  Subsequent calls to of_find_node_by_phandle()
>>>>> will incorrectly find the stale entry.  Remove the node from the
>>>>> cache.
>>>>>
>>>>> Add paranoia checks in of_find_node_by_phandle() as a second level
>>>>> of defense (do not return cached node if detached, do not add node
>>>>> to cache if detached).
>>>>>
>>>>> Reported-by: Michael Bringmann <mwb@...ux.vnet.ibm.com>
>>>>> Signed-off-by: Frank Rowand <frank.rowand@...y.com>
>>>>> ---
>>>>
>>>> Similarly here can we add:
>>>>
>>>> Fixes: 0b3ce78e90fc ("of: cache phandle nodes to reduce cost of of_find_node_by_phandle()")
>>>
>>> Yes, thanks.
>>>
>>>
>>>> Cc: stable@...r.kernel.org # v4.17+
>>>
>>> Nope, 0b3ce78e90fc does not belong in stable (it is a feature, not a bug
>>> fix).  So the bug will not be in stable.
>>
>> 0b3ce78e90fc landed in v4.17, so Michael's line above is correct.
>> Annotating it with 4.17 only saves Greg from trying and then emailing
>> us to backport this patch as it wouldn't apply.
> 
> Thanks for the correction.  I was both under-thinking and over-thinking,
> ending up with an incorrect answer.
> 
> Can you add the Cc: to version 3 patch comments (both 1/2 and 2/2) or do
> you want me to re-spin?

Now that my thinking has been straightened out, a little bit more checking
for the other pre-requisite patches show:

  v4.18: commit b9952b5218ad ("of: overlay: update phandle cache on overlay apply and remove")
  v4.19: commit e54192b48da7 ("of: fix phandle cache creation for DTs with no phandles")

These can be addressed by changing the "Cc:" to ... # v4.19+
because stable v4.17.* and v4.18.* are end of life.

Or the pre-requisites can be listed:

   # v4.17: b9952b5218ad of: overlay: update phandle cache
   # v4.17: e54192b48da7 of: fix phandle cache creation
   # v4.17

   # v4.18: e54192b48da7 of: fix phandle cache creation
   # v4.18

   # v4.19+

Do you have a preference?

-Frank
> 
> -Frank
> 
>>
>> Rob
>>
> 
>