linux-kernel - Re: rcu: Add might_sleep() check to synchronize

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Message-ID: <alpine.DEB.2.21.1803232232410.1481@nanos.tec.linutronix.de>
Date:   Fri, 23 Mar 2018 22:33:29 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Steven Rostedt <rostedt@...dmis.org>
cc:     LKML <linux-kernel@...r.kernel.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: rcu: Add might_sleep() check to synchronize_rcu()

On Fri, 23 Mar 2018, Steven Rostedt wrote:

> On Fri, 23 Mar 2018 22:12:24 +0100 (CET)
> Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> > synchronize_rcu() lacks a might_sleep() check which would have caught that
> > issue way earlier because it would trigger with the minimal debug options
> > enabled.
> > 
> > Add a might_sleep() check to catch such cases.
> 
> I'm not against the patch, but really? I would think that
> synchronize_rcu() would pretty much always schedule, and scheduling
> from atomic would have triggered with minimal debug options enabled.

Dunno. The reported splat is here:

       https://pastebin.com/raw/puvh0cXE