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Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c20
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);
}