[PATCH 6/7] memcg: no stock lock for cpu hot-unplug

[Shakeel Butt <shakeel.butt@linux.dev>]

Previously on the cpu hot-unplug, the kernel would call
drain_obj_stock() with objcg local lock. However local lock was not
needed as the stock which was accessed belongs to a dead cpu but we kept
it there to disable irqs as drain_obj_stock() may call
mod_objcg_mlstate() which required irqs disabled. However there is no
need to disable irqs now for mod_objcg_mlstate(), so we can remove the
local lock altogether from cpu hot-unplug path.

Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/memcontrol.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4f19fe9de5bf..78a41378b8f3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2050,17 +2050,8 @@ void drain_all_stock(struct mem_cgroup *root_memcg)
 
 static int memcg_hotplug_cpu_dead(unsigned int cpu)
 {
-	struct obj_stock_pcp *obj_st;
-	unsigned long flags;
-
-	obj_st = &per_cpu(obj_stock, cpu);
-
-	/* drain_obj_stock requires objstock.lock */
-	local_lock_irqsave(&obj_stock.lock, flags);
-	drain_obj_stock(obj_st);
-	local_unlock_irqrestore(&obj_stock.lock, flags);
-
 	/* no need for the local lock */
+	drain_obj_stock(&per_cpu(obj_stock, cpu));
 	drain_stock_fully(&per_cpu(memcg_stock, cpu));
 
 	return 0;
-- 
2.47.1