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Date: Thu, 3 Mar 2016 13:27:16 +0200
From: Konstantin Belousov <kostikbel@gmail.com>
To: Hans Petter Selasky <hps@selasky.org>
Cc: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
Subject: Re: svn commit: r296320 - in head/sys: kern sys
Message-ID: <20160303112716.GO67250@kib.kiev.ua>
References: <201603021846.u22IkHWM010861@repo.freebsd.org>
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On Thu, Mar 03, 2016 at 11:59:36AM +0100, Hans Petter Selasky wrote:
> I believe all of these callout quirks can be avoided by using a spinlock 
> to proctect the thread callout like done in projects/hps_head. Has 
> anyone tried to reproduce the issue with projects/hps_head, before 
> making this patch?
I did not looked at your branch, but I do not like this coupling between
callbacks and thread locks.  Even more, this probably cannot make work
since thread lock is not some fixed lock at all, and introducing one
more spinlock for the coupling is excessive.

> 
> BTW: The FreeBSD kernel version should have been bumped because 
> _callout_stop_safe() is a public callout API, used by all external 
> kernel modules, which now will have undefined behaviour until recompiled.
The change was done in a way which is compatible with the pre-commit
callout_stop_safe(9)  users.  I even consider it mergeable into the
stable/10 without requiring any shims.