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

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Message-ID: <20150623110844.GG24268@pd.tnic>
Date:	Tue, 23 Jun 2015 13:08:44 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	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 Tue, Jun 23, 2015 at 10:56:24AM +0200, Ingo Molnar wrote:
> So I think the theory is that crashes do happen, and that any RCU warning only 
> matters to (usually) small race windows.
> 
> So by the time a difficult crash truly happens, exactly in that race window, we'd 
> have fixed the RCU warning long ago.
> 
> I.e. the placement of the RCU warning isn't really relevant in the long run, as it 
> should not trigger.
> 
> In the short run it's probably more important to have it first, because if we have 
> that RCU race then we don't know whether we can trust anything that happens after 
> executing the (flawed) notifier chain.
> 
> Does that logic make sense to you?

Yap, it does actually. Nice :)

Thanks!

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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