Re: [PATCH 06/17] batman-adv: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

[Vlastimil Babka]

On 10/14/24 09:08, Julia Lawall wrote:
> 
> 
> On Mon, 14 Oct 2024, Sven Eckelmann wrote:
> 
>> On Sunday, 13 October 2024 22:16:53 CEST Julia Lawall wrote:
>> > Since SLOB was removed and since
>> > commit 6c6c47b063b5 ("mm, slab: call kvfree_rcu_barrier() from kmem_cache_destroy()"),
>> > it is not necessary to use call_rcu when the callback only performs
>> > kmem_cache_free. Use kfree_rcu() directly.
>> >
>> > The changes were made using Coccinelle.
>> >
>> > Signed-off-by: Julia Lawall <Julia.Lawall@xxxxxxxx>
>> >
>> > ---
>> >  net/batman-adv/translation-table.c |   47 ++-----------------------------------
>> >  1 file changed, 3 insertions(+), 44 deletions(-)
>>
>>
>> This was tried and we noticed that it is not safe [1]. So, I would get
>> confirmation that commit 6c6c47b063b5 ("mm, slab: call kvfree_rcu_barrier()
>> from kmem_cache_destroy()") is fixing the problem which we had at that time.
>> The commit message sounds like it but I just want to be sure.
> 
> Thanks for the feedback. I think that Vlastimil Babka can help with that.

Hi, yeah the batman-adv issue was how we learned about the problem and the
series of commits leading to and including 6c6c47b063b5 was done exactly to
address the kmem_cache_destroy() on module unload issue, and unblock the
conversion to kfree_rcu().

Thanks, Vlastimil

> julia