linux-kernel - Re: [PATCH v3 4/4] mm/vmap: move BUG_ON() check to the unlink

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Message-ID: <20190527140240.6lzhunbc4py573yl@pc636>
Date:   Mon, 27 May 2019 16:02:40 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     "Uladzislau Rezki (Sony)" <urezki@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        Roman Gushchin <guro@...com>, Hillf Danton <hdanton@...a.com>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH v3 4/4] mm/vmap: move BUG_ON() check to the unlink_va()

> > Move the BUG_ON()/RB_EMPTY_NODE() check under unlink_va()
> > function, it means if an empty node gets freed it is a BUG
> > thus is considered as faulty behaviour.
> 
> Can we switch it to a WARN_ON(). We are trying to remove all BUG_ON()s.
> If a user wants to crash on warning, there's a sysctl for that. But
> crashing the system can make it hard to debug. Especially if it is hit
> by someone without a serial console, and the machine just hangs in X.
> That is very annoying.
> 
> With a WARN_ON, you at least get a chance to see the crash dump.
Yes we can. Even though it is considered as faulty behavior it is not
a good reason to trigger a BUG. I will fix that.

Thank you!

--
Vlad Rezki