From: Roman Gushchin <guro@xxxxxx> Subject: mm: memcg/slab: synchronize access to kmem_cache dying flag using a spinlock 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@xxxxxx Signed-off-by: Roman Gushchin <guro@xxxxxx> Acked-by: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Waiman Long <longman@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: Andrei Vagin <avagin@xxxxxxxxx> Cc: Qian Cai <cai@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/slab_common.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) --- a/mm/slab_common.c~mm-synchronize-access-to-kmem_cache-dying-flag-using-a-spinlock +++ a/mm/slab_common.c @@ -130,6 +130,7 @@ int __kmem_cache_alloc_bulk(struct kmem_ #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(stru __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 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 _
