lkml.org 
[lkml]   [2022]   [Jun]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 1/3] mm/slub: fix the race between validate_slab and slab_free
From


On 6/8/22 8:23 PM, Christoph Lameter wrote:
> On Wed, 8 Jun 2022, Rongwei Wang wrote:
>
>> If available, I think document the issue and warn this incorrect behavior is
>> OK. But it still prints a large amount of confusing messages, and disturbs us?
>
> Correct it would be great if you could fix this in a way that does not
> impact performance.
>
>>> are current operations on the slab being validated.
>> And I am trying to fix it in following way. In a short, these changes only
>> works under the slub debug mode, and not affects the normal mode (I'm not
>> sure). It looks not elegant enough. And if all approve of this way, I can
>> submit the next version.
>
>
>>
>> Anyway, thanks for your time:).
>> -wrw
>>
>> @@ -3304,7 +3300,7 @@ static void __slab_free(struct kmem_cache *s,
> struct
>> slab *slab,
>>
>> {
>> void *prior;
>> - int was_frozen;
>> + int was_frozen, to_take_off = 0;
>> struct slab new;
>
> to_take_off has the role of !n ? Why is that needed?
>
>> - do {
>> - if (unlikely(n)) {
>> + spin_lock_irqsave(&n->list_lock, flags);
>> + ret = free_debug_processing(s, slab, head, tail, cnt, addr);
>
> Ok so the idea is to take the lock only if kmem_cache_debug. That looks
> ok. But it still adds a number of new branches etc to the free loop.
>
> Some performance tests would be useful.
Hi Christoph

Thanks for your time!
Do you have some advice in benchmarks that need me to test? And I find
that hackbench and lkp was used frequently in mm/slub.c commits[1,2].
But I have no idea how to use these two benchmarks test to cover the
above changes. Can you give some examples? Thanks very much!

Sorry for late reply!

[1]https://lore.kernel.org/lkml/20210301080404.GF12822@xsang-OptiPlex-9020/
[2]https://lore.kernel.org/linux-mm/20210128134512.GF3592@techsingularity.net/

\
 
 \ /
  Last update: 2022-06-11 06:05    [W:1.242 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site