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Date:      Tue, 15 May 2012 23:08:37 +0300
From:      Andriy Gapon <avg@FreeBSD.org>
To:        Konstantin Belousov <kostikbel@gmail.com>
Cc:        svn-src-stable@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org, svn-src-stable-9@FreeBSD.org
Subject:   Re: svn commit: r235480 - in stable/9/sys: dev/usb geom geom/mountver i386/conf kern sys
Message-ID:  <4FB2B7C5.2080604@FreeBSD.org>
In-Reply-To: <20120515182747.GD2358@deviant.kiev.zoral.com.ua>
References:  <201205151721.q4FHLlgq097452@svn.freebsd.org> <20120515182747.GD2358@deviant.kiev.zoral.com.ua>

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on 15/05/2012 21:27 Konstantin Belousov said the following:
> On Tue, May 15, 2012 at 05:21:47PM +0000, Andriy Gapon wrote:
>> Author: avg Date: Tue May 15 17:21:46 2012 New Revision: 235480 URL:
>> http://svn.freebsd.org/changeset/base/235480
>> 
>> Log: MFC r230643: stop_scheduler -> td_stopsched Modified:
>> stable/9/sys/sys/proc.h 
>> ==============================================================================
>>
>> 
--- stable/9/sys/sys/proc.h	Tue May 15 17:11:00 2012	(r235479)
>> +++ stable/9/sys/sys/proc.h	Tue May 15 17:21:46 2012	(r235480) @@ -235,6
>> +235,7 @@ struct thread { short		td_locks;	/* (k) Count of non-spin
>> locks. */ short		td_rw_rlocks;	/* (k) Count of rwlock read locks. */ 
>> short		td_lk_slocks;	/* (k) Count of lockmgr shared locks. */ +	short
>> td_stopsched;	/* (k) Scheduler stopped. */ struct turnstile *td_blocked;
>> /* (t) Lock thread is blocked on. */ const char	*td_lockname;	/* (t) Name
>> of lock blocked on. */ LIST_HEAD(, turnstile) td_contested;	/* (q)
>> Contested locks. */
>> 
> Did you verified that there is a gap between td_lk_slocks and td_blocked an
> all tier-1 architectures large enough to adopt td_stopsched without 
> changing the layout of struct thread after the new member ?

I haven't verified that. but I presumed that the gap was either 2 bytes on
32-bit architectures or 6 bytes on 64-bit ones.
What is the proper and doable way of verifying this?

> If not, this breaks KBI.

I can just revert the commit to not risk an obscure breakage.
What would you suggest?

Thank you for spotting this.
-- 
Andriy Gapon



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