linux-kernel - Re: [PATCH] net: batman-adv: Use built-in RCU list checking

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Message-ID: <1634394.jP7ydfi60B@sven-edge>
Date:   Sun, 16 Feb 2020 16:35:54 +0100
From:   Sven Eckelmann <sven@...fation.org>
To:     Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
Cc:     mareklindner@...mailbox.ch, sw@...onwunderlich.de, a@...table.cc,
        davem@...emloft.net, b.a.t.m.a.n@...ts.open-mesh.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        joel@...lfernandes.org, frextrite@...il.com,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] net: batman-adv: Use built-in RCU list checking

On Sunday, 16 February 2020 16:33:24 CET Madhuparna Bhowmik wrote:
[...]
> > Can you tell us how you've identified these four hlist_for_each_entry_rcu?
>
> The other hlist_for_each_entry_rcu() are used under the protection of
> rcu_read_lock(). We only need to pass the cond when
> hlist_for_each_entry_rcu() is used under a
> different lock (not under rcu_red_lock()) because according to the current scheme a lockdep splat
> is generated when hlist_for_each_entry_rcu() is used outside of
> rcu_read_lock() or the lockdep condition (the cond argument) evaluates
> to false. So, we need to pass this cond when it is used under the
> protection of spinlock or mutex etc. and not required if rcu_read_lock()
> is used.

I understand this part. I was asking how you've identified them. Did you use 
any tool for that? coccinelle, sparse, ...

Kind regards,
	Sven

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