On Thu, Nov 30, 2017 at 02:15:31PM -0800, akpm@xxxxxxxxxxxxxxxxxxxx wrote:
> @@ -1858,9 +1824,44 @@ static void drain_all_stock(struct mem_c
> static int memcg_hotplug_cpu_dead(unsigned int cpu)
> {
> struct memcg_stock_pcp *stock;
> + struct mem_cgroup *memcg;
>
> stock = &per_cpu(memcg_stock, cpu);
> drain_stock(stock);
> +
> + for_each_mem_cgroup(memcg) {
> + int i;
> +
> + for (i = 0; i < MEMCG_NR_STAT; i++) {
> + int nid;
> + long x;
> +
> + x = __this_cpu_xchg(memcg->stat_cpu->count[i], 0);
> + if (x)
> + atomic_long_add(x, &memcg->stat[i]);
> +
> + if (i >= NR_VM_NODE_STAT_ITEMS)
> + continue;
> +
> + for_each_node(nid) {
> + struct mem_cgroup_per_node *pn;
> +
> + pn = mem_cgroup_nodeinfo(memcg, nid);
> + x = __this_cpu_xchg(pn->lruvec_stat_cpu->count[i], 0);
> + if (x)
> + atomic_long_add(x, &pn->lruvec_stat[i]);
> + }
> + }
> +
> + for (i = 0; i < MEMCG_NR_EVENTS; i++) {
> + long x;
> +
> + x = __this_cpu_xchg(memcg->stat_cpu->events[i], 0);
> + if (x)
> + atomic_long_add(x, &memcg->events[i]);
> + }
> + }
> +
> return 0;
> }
The memcg cpu_dead callback can be called early during startup
(CONFIG_DEBUG_HOTPLUG_CPU0) with preemption enabled, which triggers a
warning in its __this_cpu_xchg() calls. But CPU locality is always
guaranteed, which is the only thing we really care about here.
Using the preemption-safe this_cpu_xchg() addresses this problem.
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
Andrew, can you please merge this fixlet into the original patch?
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 40d1ef65fbd2..e616c1b0e458 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1836,7 +1836,7 @@ static int memcg_hotplug_cpu_dead(unsigned int cpu)
int nid;
long x;
- x = __this_cpu_xchg(memcg->stat_cpu->count[i], 0);
+ x = this_cpu_xchg(memcg->stat_cpu->count[i], 0);
if (x)
atomic_long_add(x, &memcg->stat[i]);
@@ -1847,7 +1847,7 @@ static int memcg_hotplug_cpu_dead(unsigned int cpu)
struct mem_cgroup_per_node *pn;
pn = mem_cgroup_nodeinfo(memcg, nid);
- x = __this_cpu_xchg(pn->lruvec_stat_cpu->count[i], 0);
+ x = this_cpu_xchg(pn->lruvec_stat_cpu->count[i], 0);
if (x)
atomic_long_add(x, &pn->lruvec_stat[i]);
}
@@ -1856,7 +1856,7 @@ static int memcg_hotplug_cpu_dead(unsigned int cpu)
for (i = 0; i < MEMCG_NR_EVENTS; i++) {
long x;
- x = __this_cpu_xchg(memcg->stat_cpu->events[i], 0);
+ x = this_cpu_xchg(memcg->stat_cpu->events[i], 0);
if (x)
atomic_long_add(x, &memcg->events[i]);
}
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