Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 7 Sep 2022 11:56:01 +0200
From:   Frederic Weisbecker <frederic@kernel.org>
To:     Joel Fernandes <joel@joelfernandes.org>
Cc:     rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
        rushikesh.s.kadam@intel.com, urezki@gmail.com,
        neeraj.iitr10@gmail.com, paulmck@kernel.org, rostedt@goodmis.org,
        vineeth@bitbyteword.org, boqun.feng@gmail.com
Subject: Re: [PATCH v5 06/18] rcu: Introduce call_rcu_lazy() API
 implementation
Message-ID: <20220907095601.GA194889@lothringen>
References: <20220901221720.1105021-7-joel@joelfernandes.org>
 <20220902152132.GA115525@lothringen>
 <Yxa5Ch574cRZxRdo@google.com>
 <20220906151757.GA183806@lothringen>
 <cde6586e-ae61-5e85-3c9a-1ce7dd2464ed@joelfernandes.org>
 <64f5770c-df37-8975-200d-7908de23fa73@joelfernandes.org>
 <da45d265-52f9-6314-7fcd-ea71e2bf4cec@joelfernandes.org>
 <4f6061f0-0de7-2916-dc6e-9f5af9b944c0@joelfernandes.org>
 <20220906191110.GA187950@lothringen>
 <8812ea75-ef14-0d5d-19d8-bda70394b41a@joelfernandes.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <8812ea75-ef14-0d5d-19d8-bda70394b41a@joelfernandes.org>
Precedence: bulk

On Tue, Sep 06, 2022 at 10:56:01PM -0400, Joel Fernandes wrote:
> On the issue of regressions with non-lazy things being treated as lazy, I was
> thinking of adding a bounded-time-check to:
> 
> [PATCH v5 08/18] rcu: Add per-CB tracing for queuing, flush and invocation.
> 
> Where, if a non-lazy CB takes an abnormally long time to execute (say it was
> subject to a race-condition), it would splat. This can be done because I am
> tracking the queue-time in the rcu_head in that patch.
> 
> On another note, boot time regressions show up pretty quickly (at least on
> ChromeOS) when non-lazy things become lazy and so far with the latest code it
> has fortunately been pretty well behaved.

Makes sense. We definetly need some sort of detection for delayed non-lazy
callbacks.

Thanks!

> 
> Thanks,
> 
>  - Joel