linux-kernel - Re: [PATCH] ipmi: fix suspicious RCU usage warning

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Message-ID: <Z9gVMuEMk9yNNL89@mail.minyard.net>
Date: Mon, 17 Mar 2025 07:27:30 -0500
From: Corey Minyard <corey@...yard.net>
To: Breno Leitao <leitao@...ian.org>
Cc: Rik van Riel <riel@...riel.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	openipmi-developer@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH] ipmi: fix suspicious RCU usage warning

On Mon, Mar 17, 2025 at 02:33:31AM -0700, Breno Leitao wrote:
> On Wed, Mar 12, 2025 at 01:19:32PM -0400, Rik van Riel wrote:
> > On recent kernels this warning fires:
> > 
> > drivers/char/ipmi/ipmi_msghandler.c:1238 RCU-list traversed in non-reader section!!
> > 
> > This looks like a fairly simple lockdep trigger, where
> > list_for_each_entry_rcu and list_for_each_entry_srcu are
> > functionally identical, but the lockdep annotation in
> > the former has an extra check.
> > 
> > That extra check is whether the RCU read lock is held,
> > which is not true when the code uses srcu_read_lock.
> > 
> > Get rid of the warning by using the properly annotated
> > list traversal macro.
> 
> Thanks for looking at this one.
> 
> There was a discussion about this issue a few years ago, with
> a different approach that never landed upstream.
> 
> 	https://lore.kernel.org/all/20201119123831.GH3710@minyard.net/#r

I thought this looked familiar.

Breno, I believe you suggested a change to the patch that sounded
reasonable, so I removed the patch, and then nothing happened and I
didn't follow up.

This is kind of a mess :-(.  Let me look at it.

-corey