linux-kernel - Re: [PATCH v5 06/18] rcu: Introduce call_rcu

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Date:   Wed, 7 Sep 2022 11:56:01 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        rushikesh.s.kadam@...el.com, urezki@...il.com,
        neeraj.iitr10@...il.com, paulmck@...nel.org, rostedt@...dmis.org,
        vineeth@...byteword.org, boqun.feng@...il.com
Subject: Re: [PATCH v5 06/18] rcu: Introduce call_rcu_lazy() API
 implementation

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