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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>,
	Andrew Morton <akpm@linux-foundation.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Muchun Song <muchun.song@linux.dev>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH] memcg: Remove the lockdep assert from __mod_objcg_mlstate().
Date: Tue, 28 May 2024 14:19:28 +0200	[thread overview]
Message-ID: <20240528121928.i-Gu7Jvg@linutronix.de> (raw)

The assert was introduced in the commit cited below as an insurance that
the semantic is the same after the local_irq_save() has been removed and
the function has been made static.

The original requirement to disable interrupt was due the modification
of per-CPU counters which require interrupts to be disabled because the
counter update operation is not atomic and some of the counters are
updated from interrupt context.

All callers of __mod_objcg_mlstate() acquire a lock
(memcg_stock.stock_lock) which disables interrupts on !PREEMPT_RT and
the lockdep assert is satisfied. On PREEMPT_RT the interrupts are not
disabled and the assert triggers.

The safety of the counter update is already ensured by
VM_WARN_ON_IRQS_ENABLED() which is part of memcg_stats_lock() and does
not require yet another check.

Remove the lockdep assert from __mod_objcg_mlstate().

Fixes: 91882c1617c15 ("memcg: simple cleanup of stats update functions")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 mm/memcontrol.c |    2 --
 1 file changed, 2 deletions(-)

--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3147,8 +3147,6 @@ static inline void __mod_objcg_mlstate(s
 	struct mem_cgroup *memcg;
 	struct lruvec *lruvec;
 
-	lockdep_assert_irqs_disabled();
-
 	rcu_read_lock();
 	memcg = obj_cgroup_memcg(objcg);
 	lruvec = mem_cgroup_lruvec(memcg, pgdat);


             reply	other threads:[~2024-05-28 12:19 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-05-28 12:19 Sebastian Andrzej Siewior [this message]
2024-05-28 12:34 ` [PATCH] memcg: Remove the lockdep assert from __mod_objcg_mlstate() Vlastimil Babka (SUSE)
2024-05-28 13:40   ` Sebastian Andrzej Siewior
2024-05-28 13:44     ` Vlastimil Babka (SUSE)
2024-05-28 14:13       ` [PATCH v2] " Sebastian Andrzej Siewior
2024-05-28 14:19         ` Vlastimil Babka (SUSE)
2024-05-28 14:59         ` Shakeel Butt
2024-05-28 15:07           ` Vlastimil Babka (SUSE)
2024-05-28 16:21             ` Shakeel Butt
2024-05-28 15:08           ` Sebastian Andrzej Siewior
2024-05-28 16:20             ` Shakeel Butt
2024-05-28 16:21         ` Shakeel Butt
2024-05-29  9:16         ` Michal Hocko

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