* [PATCH v3] mm/slab.c: add node spinlock protect in __cache_free_alien
@ 2020-07-30 10:19 qiang.zhang
2020-07-30 23:45 ` David Rientjes
0 siblings, 1 reply; 4+ messages in thread
From: qiang.zhang @ 2020-07-30 10:19 UTC (permalink / raw)
To: cl, penberg, rientjes, iamjoonsoo.kim, akpm; +Cc: linux-mm, linux-kernel
From: Zhang Qiang <qiang.zhang@windriver.com>
for example:
node0
cpu0 cpu1
slab_dead_cpu
>mutex_lock(&slab_mutex)
>cpuup_canceled slab_dead_cpu
>mask = cpumask_of_node(node) >mutex_lock(&slab_mutex)
>n = get_node(cachep0, node0)
>spin_lock_irq(n&->list_lock)
>if (!cpumask_empty(mask)) == true
>spin_unlock_irq(&n->list_lock)
>goto free_slab
....
>mutex_unlock(&slab_mutex)
.... >cpuup_canceled
>mask = cpumask_of_node(node)
kmem_cache_free(cachep0 ) >n = get_node(cachep0, node0)
>__cache_free_alien(cachep0 ) >spin_lock_irq(n&->list_lock)
>n = get_node(cachep0, node0) >if (!cpumask_empty(mask)) == false
>if (n->alien && n->alien[page_node]) >alien = n->alien
>alien = n->alien[page_node] >n->alien = NULL
>.... >spin_unlock_irq(&n->list_lock)
>....
Due to multiple cpu offline, The same cache in a node may be operated in
parallel,the "n->alien" should be protect.
Fixes: 6731d4f12315 ("slab: Convert to hotplug state machine")
Signed-off-by: Zhang Qiang <qiang.zhang@windriver.com>
---
v1->v2->v3:
change submission information and fixes tags.
mm/slab.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/mm/slab.c b/mm/slab.c
index a89633603b2d..290523c90b4e 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -759,8 +759,10 @@ static int __cache_free_alien(struct kmem_cache *cachep, void *objp,
n = get_node(cachep, node);
STATS_INC_NODEFREES(cachep);
+ spin_lock(&n->list_lock);
if (n->alien && n->alien[page_node]) {
alien = n->alien[page_node];
+ spin_unlock(&n->list_lock);
ac = &alien->ac;
spin_lock(&alien->lock);
if (unlikely(ac->avail == ac->limit)) {
@@ -769,14 +771,15 @@ static int __cache_free_alien(struct kmem_cache *cachep, void *objp,
}
ac->entry[ac->avail++] = objp;
spin_unlock(&alien->lock);
- slabs_destroy(cachep, &list);
} else {
+ spin_unlock(&n->list_lock);
n = get_node(cachep, page_node);
spin_lock(&n->list_lock);
free_block(cachep, &objp, 1, page_node, &list);
spin_unlock(&n->list_lock);
- slabs_destroy(cachep, &list);
}
+
+ slabs_destroy(cachep, &list);
return 1;
}
--
2.26.2
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v3] mm/slab.c: add node spinlock protect in __cache_free_alien
2020-07-30 10:19 [PATCH v3] mm/slab.c: add node spinlock protect in __cache_free_alien qiang.zhang
@ 2020-07-30 23:45 ` David Rientjes
2020-07-31 1:27 ` 回复: " Zhang, Qiang
0 siblings, 1 reply; 4+ messages in thread
From: David Rientjes @ 2020-07-30 23:45 UTC (permalink / raw)
To: qiang.zhang; +Cc: cl, penberg, iamjoonsoo.kim, akpm, linux-mm, linux-kernel
On Thu, 30 Jul 2020, qiang.zhang@windriver.com wrote:
> From: Zhang Qiang <qiang.zhang@windriver.com>
>
> for example:
> node0
> cpu0 cpu1
> slab_dead_cpu
> >mutex_lock(&slab_mutex)
> >cpuup_canceled slab_dead_cpu
> >mask = cpumask_of_node(node) >mutex_lock(&slab_mutex)
> >n = get_node(cachep0, node0)
> >spin_lock_irq(n&->list_lock)
> >if (!cpumask_empty(mask)) == true
> >spin_unlock_irq(&n->list_lock)
> >goto free_slab
> ....
> >mutex_unlock(&slab_mutex)
>
> .... >cpuup_canceled
> >mask = cpumask_of_node(node)
> kmem_cache_free(cachep0 ) >n = get_node(cachep0, node0)
> >__cache_free_alien(cachep0 ) >spin_lock_irq(n&->list_lock)
> >n = get_node(cachep0, node0) >if (!cpumask_empty(mask)) == false
> >if (n->alien && n->alien[page_node]) >alien = n->alien
> >alien = n->alien[page_node] >n->alien = NULL
> >.... >spin_unlock_irq(&n->list_lock)
> >....
>
As mentioned in the review of v1 of this patch, we likely want to do a fix
for cpuup_canceled() instead.
^ permalink raw reply [flat|nested] 4+ messages in thread
* 回复: [PATCH v3] mm/slab.c: add node spinlock protect in __cache_free_alien
2020-07-30 23:45 ` David Rientjes
@ 2020-07-31 1:27 ` Zhang, Qiang
2020-07-31 8:10 ` Zhang, Qiang
0 siblings, 1 reply; 4+ messages in thread
From: Zhang, Qiang @ 2020-07-31 1:27 UTC (permalink / raw)
To: David Rientjes; +Cc: cl, penberg, iamjoonsoo.kim, akpm, linux-mm, linux-kernel
________________________________________
发件人: David Rientjes <rientjes@google.com>
发送时间: 2020年7月31日 7:45
收件人: Zhang, Qiang
抄送: cl@linux.com; penberg@kernel.org; iamjoonsoo.kim@lge.com; akpm@linux-foundation.org; linux-mm@kvack.org; linux-kernel@vger.kernel.org
主题: Re: [PATCH v3] mm/slab.c: add node spinlock protect in __cache_free_alien
On Thu, 30 Jul 2020, qiang.zhang@windriver.com wrote:
> From: Zhang Qiang <qiang.zhang@windriver.com>
>
> for example:
> node0
> cpu0 cpu1
> slab_dead_cpu
> >mutex_lock(&slab_mutex)
> >cpuup_canceled slab_dead_cpu
> >mask = cpumask_of_node(node) >mutex_lock(&slab_mutex)
> >n = get_node(cachep0, node0)
> >spin_lock_irq(n&->list_lock)
> >if (!cpumask_empty(mask)) == true
> >spin_unlock_irq(&n->list_lock)
> >goto free_slab
> ....
> >mutex_unlock(&slab_mutex)
>
> .... >cpuup_canceled
> >mask = cpumask_of_node(node)
> kmem_cache_free(cachep0 ) >n = get_node(cachep0, node0)
> >__cache_free_alien(cachep0 ) >spin_lock_irq(n&->list_lock)
> >n = get_node(cachep0, node0) >if (!cpumask_empty(mask)) == false
> >if (n->alien && n->alien[page_node]) >alien = n->alien
> >alien = n->alien[page_node] >n->alien = NULL
> >.... >spin_unlock_irq(&n->list_lock)
> >....
>
>As mentioned in the review of v1 of this patch, we likely want to do a fix
>for cpuup_canceled() instead.
I see, you mean do fix in "cpuup_canceled" func?
^ permalink raw reply [flat|nested] 4+ messages in thread
* 回复: [PATCH v3] mm/slab.c: add node spinlock protect in __cache_free_alien
2020-07-31 1:27 ` 回复: " Zhang, Qiang
@ 2020-07-31 8:10 ` Zhang, Qiang
0 siblings, 0 replies; 4+ messages in thread
From: Zhang, Qiang @ 2020-07-31 8:10 UTC (permalink / raw)
To: David Rientjes; +Cc: cl, penberg, iamjoonsoo.kim, akpm, linux-mm, linux-kernel
________________________________________
发件人: Zhang, Qiang <Qiang.Zhang@windriver.com>
发送时间: 2020年7月31日 9:27
收件人: David Rientjes
抄送: cl@linux.com; penberg@kernel.org; iamjoonsoo.kim@lge.com; akpm@linux-foundation.org; linux-mm@kvack.org; linux-kernel@vger.kernel.org
主题: 回复: [PATCH v3] mm/slab.c: add node spinlock protect in __cache_free_alien
________________________________________
发件人: David Rientjes <rientjes@google.com>
发送时间: 2020年7月31日 7:45
收件人: Zhang, Qiang
抄送: cl@linux.com; penberg@kernel.org; iamjoonsoo.kim@lge.com; akpm@linux-foundation.org; linux-mm@kvack.org; linux-kernel@vger.kernel.org
主题: Re: [PATCH v3] mm/slab.c: add node spinlock protect in __cache_free_alien
On Thu, 30 Jul 2020, qiang.zhang@windriver.com wrote:
> From: Zhang Qiang <qiang.zhang@windriver.com>
>
> for example:
> node0
> cpu0 cpu1
> slab_dead_cpu
> >mutex_lock(&slab_mutex)
> >cpuup_canceled slab_dead_cpu
> >mask = cpumask_of_node(node) >mutex_lock(&slab_mutex)
> >n = get_node(cachep0, node0)
> >spin_lock_irq(n&->list_lock)
> >if (!cpumask_empty(mask)) == true
> >spin_unlock_irq(&n->list_lock)
> >goto free_slab
> ....
> >mutex_unlock(&slab_mutex)
>
> .... >cpuup_canceled
> >mask = cpumask_of_node(node)
> kmem_cache_free(cachep0 ) >n = get_node(cachep0, node0)
> >__cache_free_alien(cachep0 ) >spin_lock_irq(n&->list_lock)
> >n = get_node(cachep0, node0) >if (!cpumask_empty(mask)) == false
> >if (n->alien && n->alien[page_node]) >alien = n->alien
> >alien = n->alien[page_node] >n->alien = NULL
> >.... >spin_unlock_irq(&n->list_lock)
> >....
>
>As mentioned in the review of v1 of this patch, we likely want to do a fix
>for cpuup_canceled() instead.
>I see, you mean do fix in "cpuup_canceled" func?
I'm very sorry, due to cpu_down receive gobal "cpu_hotplug_lock" write lock protect. multiple cpu offline is serial，the scenario I described above does not exist.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2020-07-30 10:19 [PATCH v3] mm/slab.c: add node spinlock protect in __cache_free_alien qiang.zhang
2020-07-30 23:45 ` David Rientjes
2020-07-31 1:27 ` 回复: " Zhang, Qiang
2020-07-31 8:10 ` Zhang, Qiang
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