linux-kernel - Re: [RFC PATCH for 4.21 03/16] mm: Replace BUG_ON() by WARN_ON() in vm_unmap

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Message-ID: <20181101144623.61d43102@gandalf.local.home>
Date:   Thu, 1 Nov 2018 14:46:23 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Boqun Feng <boqun.feng@...il.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>,
        Dave Watson <davejwatson@...com>, Paul Turner <pjt@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Russell King <linux@....linux.org.uk>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andi Kleen <andi@...stfloor.org>, Chris Lameter <cl@...ux.com>,
        Ben Maurer <bmaurer@...com>,
        Josh Triplett <josh@...htriplett.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Matthew Wilcox <mawilcox@...rosoft.com>
Subject: Re: [RFC PATCH for 4.21 03/16] mm: Replace BUG_ON() by WARN_ON() in
 vm_unmap_ram()

On Thu, 1 Nov 2018 13:21:12 +0100 (CET)
Thomas Gleixner <tglx@...utronix.de> wrote:

> Mathieu,
> 
> On Thu, 1 Nov 2018, Mathieu Desnoyers wrote:
> 
> > It is encouraged to warn and return rather than use BUG_ON() when
> > the condition can be recovered from in ways that are more graceful than
> > halting the whole system.  
> 
> You're failing to desribe how that graceful recovery works.
> 

I think the graceful recovery is to simply return:

	if (WARN_ON(cond))
		return;

is better than just

	BUG_ON(cond);

As that's what Linus made pretty clear at the Maintainer's Summit.

-- Steve