linux-kernel - [RFC PATCH 08/10] memcg: assert in_task for couple of local

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Message-ID: <20250314061511.1308152-9-shakeel.butt@linux.dev>
Date: Thu, 13 Mar 2025 23:15:09 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Muchun Song <muchun.song@...ux.dev>,
	Vlastimil Babka <vbabka@...e.cz>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-mm@...ck.org,
	cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Meta kernel team <kernel-team@...a.com>
Subject: [RFC PATCH 08/10] memcg: assert in_task for couple of local_lock holders

The drain_local_stock() and memcg_hotplug_cpu_dead() only run in task
context, so there is no need to localtry_trylock_irqsave() the local
stock_lock in those functions. The plan is to convert all stock_lock
users which can be called in multiple context to use
localtry_trylock_irqsave() and subsequently switch to non-irq disabling
interface. So, for functions which are never called in non-task context,
this patch adds the asserts.

Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
---
 mm/memcontrol.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index dfe9c2eb7816..c803d2f5e322 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1857,6 +1857,8 @@ static void drain_local_stock(struct work_struct *dummy)
 	struct memcg_stock_pcp *stock;
 	unsigned long flags;
 
+	lockdep_assert_once(in_task());
+
 	/*
 	 * The only protection from cpu hotplug (memcg_hotplug_cpu_dead) vs.
 	 * drain_stock races is that we always operate on local CPU stock
@@ -1953,6 +1955,8 @@ static int memcg_hotplug_cpu_dead(unsigned int cpu)
 	struct memcg_stock_pcp *stock;
 	unsigned long flags;
 
+	lockdep_assert_once(in_task());
+
 	stock = &per_cpu(memcg_stock, cpu);
 
 	/* drain_obj_stock requires stock_lock */
-- 
2.47.1