diff options
| -rw-r--r-- | mm/memcontrol.c | 20 |
1 files changed, 15 insertions, 5 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 15af3da5af02..696c6529e900 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1777,6 +1777,10 @@ static void drain_local_stock(struct work_struct *dummy) struct memcg_stock_pcp *stock; unsigned long flags; + /* + * The only protection from memory hotplug vs. drain_stock races is + * that we always operate on local CPU stock here with IRQ disabled + */ local_irq_save(flags); stock = this_cpu_ptr(&memcg_stock); @@ -1821,27 +1825,33 @@ static void drain_all_stock(struct mem_cgroup *root_memcg) /* If someone's already draining, avoid adding running more workers. */ if (!mutex_trylock(&percpu_charge_mutex)) return; - /* Notify other cpus that system-wide "drain" is running */ - get_online_cpus(); + /* + * Notify other cpus that system-wide "drain" is running + * We do not care about races with the cpu hotplug because cpu down + * as well as workers from this path always operate on the local + * per-cpu data. CPU up doesn't touch memcg_stock at all. + */ curcpu = get_cpu(); for_each_online_cpu(cpu) { struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu); struct mem_cgroup *memcg; memcg = stock->cached; - if (!memcg || !stock->nr_pages) + if (!memcg || !stock->nr_pages || !css_tryget(&memcg->css)) continue; - if (!mem_cgroup_is_descendant(memcg, root_memcg)) + if (!mem_cgroup_is_descendant(memcg, root_memcg)) { + css_put(&memcg->css); continue; + } if (!test_and_set_bit(FLUSHING_CACHED_CHARGE, &stock->flags)) { if (cpu == curcpu) drain_local_stock(&stock->work); else schedule_work_on(cpu, &stock->work); } + css_put(&memcg->css); } put_cpu(); - put_online_cpus(); mutex_unlock(&percpu_charge_mutex); } |