mm: memcg/slab: synchronize access to kmem_cache dying flag using a spinlock (63b02ef7) · Commits · 戴 / test

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 <guro@fb.com> Acked-by:

Vladimir Davydov <vdavydov.dev@gmail.com> Reviewed-by:

Shakeel Butt <shakeelb@google.com> Cc: Christoph Lameter <cl@linux.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Waiman Long <longman@redhat.com> Cc: David Rientjes <rientjes@google.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Andrei Vagin <avagin@gmail.com> Cc: Qian Cai <cai@lca.pw> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/slab_common.c

+12 −3

Original line number	Diff line number	Diff line
		@@ -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)
		{
		@@ -734,14 +735,22 @@ static void kmemcg_cache_deactivate(struct kmem_cache *s)

		__kmemcg_cache_deactivate(s);

		/*
		* 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.work_fn = __kmemcg_cache_deactivate_after_rcu;
		call_rcu(&s->memcg_params.rcu_head, kmemcg_rcufn);
		unlock:
		spin_unlock_irq(&memcg_kmem_wq_lock);
		}

		void memcg_deactivate_kmem_caches(struct mem_cgroup *memcg)
		@@ -851,9 +860,9 @@ 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);

		/*
		* SLAB and SLUB deactivate the kmem_caches through call_rcu. Make

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