linux-kernel - Re: [PATCH v2] memcg: simple cleanup of stats update functions

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Date: Mon, 27 May 2024 17:22:00 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Shakeel Butt <shakeel.butt@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Muchun Song <muchun.song@...ux.dev>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2] memcg: simple cleanup of stats update functions

On 2024-04-20 16:25:05 [-0700], Shakeel Butt wrote:
> mod_memcg_lruvec_state() is never called from outside of memcontrol.c
> and with always irq disabled. So, replace it with the irq disabled
> version and add an assert that irq is disabled in the caller.

unless PREEMPT_RT is enabled. In that case IRQs are not disabled as part
of local_lock_irqsave(&memcg_stock.stock_lock, …) leading to:

| ------------[ cut here ]------------
| WARNING: CPU: 0 PID: 1 at mm/memcontrol.c:3150 __mod_objcg_mlstate+0xc2/0x110
| CPU: 0 PID: 1 Comm: systemd Not tainted 6.10.0-rc1-rt0+ #17
| Call Trace:
|  <TASK>
|  mod_objcg_state+0x2b3/0x320
|  __memcg_slab_post_alloc_hook+0x13c/0x340
|  kmem_cache_alloc_lru_noprof+0x2bd/0x2e0
|  alloc_inode+0x59/0xc0
|  iget_locked+0xf0/0x290

suggestions?

Sebastian