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Date: Tue, 09 Sep 2014 07:18:22 -0400
From: Peter Hurley <peter@hurleysoftware.com>
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To: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
 "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: bit fields && data tearing
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Cc: Jakub Jelinek <jakub@redhat.com>,
 "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
 Tony Luck <tony.luck@intel.com>,
 "linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
 Oleg Nesterov <oleg@redhat.com>,
 "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
 David Laight <David.Laight@ACULAB.COM>, Paul Mackerras <paulus@samba.org>,
 linux-alpha@vger.kernel.org, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
 "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
 Miroslav Franc <mfranc@redhat.com>, Richard Henderson <rth@twiddle.net>
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On 09/08/2014 03:17 PM, One Thousand Gnomes wrote:
>>> I think the whole "removing Alpha EV5" support is basically bonkers. Just
>>> use set_bit in the tty layer. Alpha will continue to work as well as it
>>> always has done and you won't design out support for any future processor
>>> that turns out not to do byte aligned stores.
>>>
>>> Alan
>>>
>>
>> Is *that* what we are talking about?  I was added to this conversation
>> in the middle where it had already generalized, so I had no idea.
>>
>> 	-hpa
> 
> Yes there are some flags in the tty layer that are vulnerable to this
> (although they've been vulnerable to it and missing a lock since last
> century with no known ill effects).

That observation cuts both ways; I'm willing to leave it vulnerable with
'no known ill effects' on the Alpha.