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Date: Thu, 2 Oct 2025 07:49:03 +0200
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Kuniyuki Iwashima <kuniyu@google.com>
Cc: Tejun Heo <tj@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>,
	Michal =?utf-8?Q?Koutn=C3=BD?= <mkoutny@suse.com>,
	Clark Williams <clrkwllms@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Tiffany Yang <ynaffit@google.com>,
	Kuniyuki Iwashima <kuni1840@gmail.com>, cgroups@vger.kernel.org,
	linux-rt-devel@lists.linux.dev,
	syzbot+27a2519eb4dad86d0156@syzkaller.appspotmail.com
Subject: Re: [PATCH] cgroup: Disable preemption for cgrp->freezer.freeze_seq
 when CONFIG_PREEMPT_RT=y.
Message-ID: <20251002054903.kzlPcvnz@linutronix.de>
References: <20251002052215.1433055-1-kuniyu@google.com>
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In-Reply-To: <20251002052215.1433055-1-kuniyu@google.com>

On 2025-10-02 05:22:07 [+0000], Kuniyuki Iwashima wrote:
> syzbot reported the splat below. [0]
> 
> Commit afa3701c0e45 ("cgroup: cgroup.stat.local time accounting")
> introduced cgrp->freezer.freeze_seq.
> 
> The writer side is under spin_lock_irq(), but the section is still
> preemptible with CONFIG_PREEMPT_RT=y.
> 
> Let's wrap the section with preempt_{disable,enable}_nested().

Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Sebastian