From 763b04c6b26bc12c2df36390210e5377b241a8a8 Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Thu, 11 Jul 2019 20:56:24 -0700 Subject: [PATCH] mm: memcg/slab: synchronize access to kmem_cache dying flag using a spinlock [ Upstream commit 63b02ef7dc4ec239df45c018ac0adbd02ba30a0c ] Currently the memcg_params.dying flag and the corresponding workqueue used for the asynchronous deactivation of kmem_caches is synchronized using the slab_mutex. It makes impossible to check this flag from the irq context, which will be required in order to implement asynchronous release of kmem_caches. So let's switch over to the irq-save flavor of the spinlock-based synchronization. Link: http://lkml.kernel.org/r/20190611231813.3148843-8-guro@fb.com Signed-off-by: Roman Gushchin Acked-by: Vladimir Davydov Reviewed-by: Shakeel Butt Cc: Christoph Lameter Cc: Johannes Weiner Cc: Michal Hocko Cc: Waiman Long Cc: David Rientjes Cc: Joonsoo Kim Cc: Pekka Enberg Cc: Andrei Vagin Cc: Qian Cai Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/slab_common.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/mm/slab_common.c b/mm/slab_common.c index b5776b1301f0..3dbf693527dd 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -130,6 +130,7 @@ int __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t nr, #ifdef CONFIG_MEMCG_KMEM LIST_HEAD(slab_root_caches); +static DEFINE_SPINLOCK(memcg_kmem_wq_lock); void slab_init_memcg_params(struct kmem_cache *s) { @@ -717,14 +718,22 @@ void slab_deactivate_memcg_cache_rcu_sched(struct kmem_cache *s, WARN_ON_ONCE(s->memcg_params.deact_fn)) return; + /* + * memcg_kmem_wq_lock is used to synchronize memcg_params.dying + * flag and make sure that no new kmem_cache deactivation tasks + * are queued (see flush_memcg_workqueue() ). + */ + spin_lock_irq(&memcg_kmem_wq_lock); if (s->memcg_params.root_cache->memcg_params.dying) - return; + goto unlock; /* pin memcg so that @s doesn't get destroyed in the middle */ css_get(&s->memcg_params.memcg->css); s->memcg_params.deact_fn = deact_fn; call_rcu_sched(&s->memcg_params.deact_rcu_head, kmemcg_deactivate_rcufn); +unlock: + spin_unlock_irq(&memcg_kmem_wq_lock); } void memcg_deactivate_kmem_caches(struct mem_cgroup *memcg) @@ -834,9 +843,9 @@ static int shutdown_memcg_caches(struct kmem_cache *s) static void flush_memcg_workqueue(struct kmem_cache *s) { - mutex_lock(&slab_mutex); + spin_lock_irq(&memcg_kmem_wq_lock); s->memcg_params.dying = true; - mutex_unlock(&slab_mutex); + spin_unlock_irq(&memcg_kmem_wq_lock); /* * SLUB deactivates the kmem_caches through call_rcu_sched. Make