[SLOF] [PATCH slof] fdt: Avoid recursion when traversing tree

[Alexey Kardashevskiy]

On 17/07/2020 17:42, Greg Kurz wrote:
> On Fri, 17 Jul 2020 10:34:40 +1000
> Alexey Kardashevskiy <aik at ozlabs.ru> wrote:
> 
>>
>>
>> On 17/07/2020 01:54, Greg Kurz wrote:
>>> Hi Alexey,
>>>
>>> It seems it did again ! I haven't received this in my inbox, despite you've
>>> put me on Cc... :-\
>>>
>>> On Thu, 16 Jul 2020 14:55:42 +1000
>>> Alexey Kardashevskiy <aik at ozlabs.ru> wrote:
>>>
>>>> A loop over peers does not need recursion which becomes a problem with
>>>> hundreds devices.
>>>>
>>>
>>> You're likely right but, per curiosity, do you have some numbers to
>>> share ?
>>
>>
>> This was discovered with just "-smp 2048,cores=512,threads=4" and the
>> results were either "cas not implemented" or some other weird XIVE
>> messages (I did not see any but Anton did).
>>
> 
> Oh, I was thinking to something like "it took 30 minutes to boot", but

Well, this too but it is just some waiting :)

> you seem to be talking about dysfunction of SLOF, which would be caused
> by stack exhaustion if I understand Segher's anwser correctly, right ?


Right. I am a bit surprised SLOF did not barf with "stack overflow" though.


> 
>>
>>
>>>
>>>> Cc: Greg Kurz <groug at kaod.org>
>>>> Fixes: efa56b851fab ("fdt: Delete nodes of devices removed between boot and CAS")
>>>> Suggested-by: Jordan Niethe <jniethe5 at gmail.com>
>>>> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
>>>> ---
>>>>  board-qemu/slof/fdt.fs | 27 +++++++++++++++------------
>>>>  1 file changed, 15 insertions(+), 12 deletions(-)
>>>>
>>>> diff --git a/board-qemu/slof/fdt.fs b/board-qemu/slof/fdt.fs
>>>> index 7da4ff066702..03b1d4034d0a 100644
>>>> --- a/board-qemu/slof/fdt.fs
>>>> +++ b/board-qemu/slof/fdt.fs
>>>> @@ -636,20 +636,23 @@ r> drop
>>>>      THEN
>>>>  ;
>>>>  
>>>> -: (fdt-cas-search-obsolete-nodes) ( start node -- )
>>>> -    dup IF
>>>> -	dup child 2 pick swap recurse
>>>> -	dup peer 2 pick swap recurse
>>>> -
>>>> -	dup fdt-cas-node-obsolete? IF
>>>> -	    fdt-debug IF dup ." Deleting obsolete node: " dup .node ." = " . cr THEN
>>>> -	    dup delete-node
>>>> -	THEN
>>>> +: (fdt-cas-search-obsolete-nodes) ( node -- )
>>>> +    dup child
>>>> +    BEGIN
>>>> +	dup
>>>> +    WHILE
>>>> +	dup recurse
>>>> +	peer
>>>> +    REPEAT
>>>> +    drop
>>>> +    dup fdt-cas-node-obsolete? IF
>>>> +        fdt-debug IF dup ." Deleting obsolete node: " dup .node ." = " . cr THEN
>>>> +        dup delete-node
>>>>      THEN
>>>> -    2drop
>>>> +    drop
>>>>  ;
>>>>  
>>>> -: fdt-cas-delete-obsolete-nodes ( start -- )
>>>> +: fdt-cas-delete-obsolete-nodes ( -- )
>>>>      s" /" find-device get-node (fdt-cas-search-obsolete-nodes)
>>>>      fdt-cas-delete-obsolete-aliases
>>>>  ;
>>>> @@ -657,7 +660,7 @@ r> drop
>>>>  : fdt-fix-cas-node ( start -- )
>>>>      fdt-generation# 1+ to fdt-generation#
>>>>      0 to fdt-cas-pass dup (fdt-fix-cas-node) drop \ Add phandles
>>>> -    dup fdt-cas-delete-obsolete-nodes             \ Delete removed devices
>>>> +    fdt-cas-delete-obsolete-nodes             \ Delete removed devices
>>>
>>> Maybe keep the comment aligned with the other ones ?
>>
>> May be :)
>>
>>>
>>> Reviewed-by: Greg Kurz <groug at kaod.org>
>>
>>
>> Thanks!
>>
>>>
>>>>      1 to fdt-cas-pass dup (fdt-fix-cas-node) drop \ Patch+add other properties
>>>>      2 to fdt-cas-pass dup (fdt-fix-cas-node) drop \ Delete phandles from pass 0
>>>>      drop
>>>
>>
> 

-- 
Alexey