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Message-Id: <e2923bb7-19bf-b303-9457-49040acffe92@de.ibm.com>
Date: Mon, 25 Nov 2019 09:00:56 +0100
From: Christian Borntraeger <borntraeger@...ibm.com>
To: Roman Gushchin <guro@...com>
Cc: "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"hannes@...xchg.org" <hannes@...xchg.org>,
Kernel Team <Kernel-team@...com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"longman@...hat.com" <longman@...hat.com>,
"shakeelb@...gle.com" <shakeelb@...gle.com>,
"vdavydov.dev@...il.com" <vdavydov.dev@...il.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Janosch Frank <frankja@...ux.ibm.com>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: WARNING bisected (was Re: [PATCH v7 08/10] mm: rework non-root
kmem_cache lifecycle management)
On 24.11.19 01:39, Roman Gushchin wrote:
> On Fri, Nov 22, 2019 at 05:28:46PM +0100, Christian Borntraeger wrote:
>> On 21.11.19 19:45, Roman Gushchin wrote:
>>> I see. Do you know, which kmem_cache it is? If not, can you, please,
>>> figure it out?
>>
>> The release function for that ref is kmemcg_cache_shutdown.
>>
>
> Hi Christian!
>
> Can you, please, test if the following patch resolves the problem?
Yes, it does.
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 8afa188f6e20..628e5f0ee19e 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -888,6 +888,8 @@ static int shutdown_memcg_caches(struct kmem_cache *s)
>
> static void flush_memcg_workqueue(struct kmem_cache *s)
> {
> + bool wait_for_children;
> +
> spin_lock_irq(&memcg_kmem_wq_lock);
> s->memcg_params.dying = true;
> spin_unlock_irq(&memcg_kmem_wq_lock);
> @@ -904,6 +906,13 @@ static void flush_memcg_workqueue(struct kmem_cache *s)
> * previous workitems on workqueue are processed.
> */
> flush_workqueue(memcg_kmem_cache_wq);
> +
> + mutex_lock(&slab_mutex);
> + wait_for_children = !list_empty(&s->memcg_params.children);
> + mutex_unlock(&slab_mutex);
Not sure if (for reading) we really need the mutex.
> +
> + if (wait_for_children)
> + rcu_barrier();
> }
> #else
> static inline int shutdown_memcg_caches(struct kmem_cache *s)
>
> --
>
> Thanks!
>
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