Commit 0ccf1806 authored by Shakeel Butt's avatar Shakeel Butt Committed by Andrew Morton
Browse files

memcg: no stock lock for cpu hot-unplug 

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.

Link: https://lkml.kernel.org/r/20250514184158.3471331-7-shakeel.butt@linux.dev


Signed-off-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent eee8a177

mm/memcontrol.c

+1 −10
Original line number Diff line number Diff line
@@ -2023,17 +2023,8 @@ 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;