linux-kernel - Re: [linux-next:master] [tracing] dfe0d675df: WARNING:suspicious_RCU

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Message-ID: <20250828103433.1498f8a7@gandalf.local.home>
Date: Thu, 28 Aug 2025 10:34:33 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Menglong Dong <menglong8.dong@...il.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, oe-lkp@...ts.linux.dev, kernel
 test robot <oliver.sang@...el.com>, lkp@...el.com, Menglong Dong
 <dongml2@...natelecom.cn>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [linux-next:master] [tracing] dfe0d675df:
 WARNING:suspicious_RCU_usage

On Thu, 28 Aug 2025 17:09:35 +0800
Menglong Dong <menglong8.dong@...il.com> wrote:

> > [  354.955971][ T4652]  dump_stack_lvl+0x7c/0x90
> > [  354.955978][ T4652]  lockdep_rcu_suspicious+0x14f/0x1c0
> > [  354.955987][ T4652]  __rhashtable_lookup+0x1e0/0x260  
> 
> rcu_read_lock() is not needed in fprobe_entry, but
> rcu_dereference_check() is used in rhltable_lookup(), which
> causes this warning.

Why is rcu_read_lock() not needed in fprobe_entry()?

-- Steve

> 
> Adding rcu_read_lock() here is able to suppress this warning.
> Maybe we need only rcu_lock_acquire(&rcu_lock_map) here,
> but it's not a common usage. What do you think, Masami?