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

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Message-ID: <20200216155243.GB4542@madhuparna-HP-Notebook>
Date:   Sun, 16 Feb 2020 21:22:44 +0530
From:   Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>
To:     Sven Eckelmann <sven@...fation.org>
Cc:     Madhuparna Bhowmik <madhuparnabhowmik10@...il.com>,
        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 Sun, Feb 16, 2020 at 04:35:54PM +0100, Sven Eckelmann wrote:
> 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, ...
>
Hi,

Not really, I did it manually by inspecting each occurence.
Thank you,
Madhuparna

> Kind regards,
> 	Sven