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Date:   Thu, 11 Jul 2019 19:52:39 -0400
From:   Joel Fernandes <joel@joelfernandes.org>
To:     linux-kernel@vger.kernel.org
Cc:     Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Bjorn Helgaas <bhelgaas@google.com>,
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        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
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        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Rasmus Villemoes <rasmus.villemoes@prevas.dk>,
        rcu@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>,
        Tejun Heo <tj@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, will@kernel.org,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>
Subject: Re: [PATCH v1 0/6] Harden list_for_each_entry_rcu() and family
Message-ID: <20190711235239.GA221389@google.com>
References: <20190711234401.220336-1-joel@joelfernandes.org>
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On Thu, Jul 11, 2019 at 07:43:55PM -0400, Joel Fernandes (Google) wrote:
> Hi,
> This series aims to provide lockdep checking to RCU list macros.
> 
> RCU has a number of primitives for "consumption" of an RCU protected pointer.
> Most of the time, these consumers make sure that such accesses are under a RCU
> reader-section (such as rcu_dereference{,sched,bh} or under a lock, such as
> with rcu_dereference_protected()).
> 
> However, there are other ways to consume RCU pointers, such as by
> list_for_each_entry_rcu or hlist_for_each_enry_rcu. Unlike the rcu_dereference
> family, these consumers do no lockdep checking at all. And with the growing
> number of RCU list uses (1000+), it is possible for bugs to creep in and go
> unnoticed which lockdep checks can catch.

I forgot to add in my cover letter, I have kept this option default-disabled
under a new config: CONFIG_PROVE_RCU_LIST. This is so that until all users
are converted to pass the optional argument, we should keep the check
disabled. There are about a 1000 or so users and it is not possible to pass
in the optional lockdep expression in a single series since it is done on a
case-by-case basis. I did convert a few users in this series itself.

Also, I plans to update the RCU documentation as well which I will do, but do
review this series and thank you!