netdev - Re: [PATCH net] test_rhashtable: Add missing rcu_read

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Date:   Thu, 8 Mar 2018 19:10:47 +0200
From:   Paul Blakey <paulb@...lanox.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     paulb@...lanox.com, Thomas Graf <tgraf@...g.ch>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net] test_rhashtable: Add missing rcu_read_lock()



On 08/03/2018 17:58, Herbert Xu wrote:
> On Thu, Mar 08, 2018 at 01:54:57PM +0200, Paul Blakey wrote:
>> Suppress "suspicious rcu_dereference_protected() usage!" on duplicate
>> insertion test.
>>
>> Fixes: 499ac3b60f65 ('test_rhashtable: add test case for rhl_table with duplicate objects')
>> Signed-off-by: Paul Blakey <paulb@...lanox.com>
> 
> This shouldn't be doing a table walk in the first place.
> 
> You should convert it to using the table walk interface.
> 
> Direct table walks are forbidden because they will break when
> you hit a resize.
> 
> Cheers,
> 


I know but I wanted to show the inner structure for the failure case, 
iirc walk doesn't provide this.

                ---- ht: ----
                bucket[1] -> [[ val 1 (tid=0) ]] -> [[ val 21 (tid=1) ]]
                -------------
[ 3599.715501]
                ---- ht: ----
                bucket[1] -> [[ val 1 (tid=2),  val 1 (tid=0) ]] -> [[ 
val 21 (tid=1) ]]
                -------------
[ 3599.738600]
                ---- ht: ----
                bucket[1] -> [[ val 21 (tid=1) ]] -> [[ val 1 (tid=0) ]]
                -------------
[ 3599.759443]
                ---- ht: ----
                bucket[1] -> [[ val 21 (tid=1) ]] -> [[ val 1 (tid=2), 
val 1 (tid=0) ]]