linux-kernel - Re: [PATCH v2 03/14] notifiers: Assert that RCU is watching in notify

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Date:	Mon, 22 Jun 2015 10:03:30 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Kees Cook <keescook@...omium.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Brian Gerst <brgerst@...il.com>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	X86 ML <x86@...nel.org>, Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH v2 03/14] notifiers: Assert that RCU is watching in notify_die

On Mon, Jun 22, 2015 at 9:33 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Mon, Jun 22, 2015 at 09:26:13AM -0700, Andy Lutomirski wrote:
>> notify_die is misnamed and has little to do with death. It's really
>> just notifying about an exception, and we might end up oopsing,
>> sending a signal, or neither.
>
> But if we oops and wedge solid afterwards, it might happen that only the
> first splat comes out on the console, no? And that will be the lockdep
> splat which would be useless for debugging the actual problem...
>

The rcu_lockdep_assert should be merely a warning, not a full OOPS.  I
think that, if rcu_lockdep_assert hangs, then we should fix that
rather than avoiding debugging checks.

--Andy
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