linux-kernel - Re: [PATCH v4 29/35] mm: slub: Move flush_cpu_slab() invocations __free

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Date:   Wed, 11 Aug 2021 10:55:34 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Qian Cai <quic_qiancai@...cinc.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Mike Galbraith <efault@....de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH v4 29/35] mm: slub: Move flush_cpu_slab() invocations
 __free_slab() invocations out of IRQ context

On 8/10/21 4:33 PM, Vlastimil Babka wrote:
> On 8/9/21 3:41 PM, Qian Cai wrote:
> 
>>>  static void flush_all(struct kmem_cache *s)
>>>  {
>>> -	on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1);
>>> +	struct slub_flush_work *sfw;
>>> +	unsigned int cpu;
>>> +
>>> +	mutex_lock(&flush_lock);
>> 
>> Vlastimil, taking the lock here could trigger a warning during memory offline/online due to the locking order:
>> 
>> slab_mutex -> flush_lock
> 
> Here's the full fixup, also incorporating Mike's fix. Thanks.
> 

One more fixup, sorry for the churn.
----8<----
>From 7cfe3fb1bcd6e589199b10bef480ed097ba9de14 Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@...e.cz>
Date: Wed, 11 Aug 2021 10:51:14 +0200
Subject: [PATCH] mm, slub: fix memory and cpu hotplug related lock ordering
 issues - fix

Make __kmem_cache_do_shrink static to silence "no previous prototype" warning.

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slub.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index 152487f84025..c9531e03addd 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4393,7 +4393,7 @@ EXPORT_SYMBOL(kfree);
  * being allocated from last increasing the chance that the last objects
  * are freed in them.
  */
-int __kmem_cache_do_shrink(struct kmem_cache *s)
+static int __kmem_cache_do_shrink(struct kmem_cache *s)
 {
 	int node;
 	int i;
-- 
2.32.0