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Date:      Thu, 21 May 2009 15:29:57 +0200
From:      Attilio Rao <attilio@freebsd.org>
To:        Kostik Belousov <kostikbel@gmail.com>
Cc:        svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org
Subject:   Re: svn commit: r192535 - head/sys/kern
Message-ID:  <3bbf2fe10905210629p46c7a204v6863aaba77354462@mail.gmail.com>
In-Reply-To: <20090521132641.GJ1927@deviant.kiev.zoral.com.ua>
References:  <200905211322.n4LDM73t067924@svn.freebsd.org> <20090521132641.GJ1927@deviant.kiev.zoral.com.ua>

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2009/5/21 Kostik Belousov <kostikbel@gmail.com>:
> On Thu, May 21, 2009 at 01:22:07PM +0000, Attilio Rao wrote:
>> Author: attilio
>> Date: Thu May 21 13:22:07 2009
>> New Revision: 192535
>> URL: http://svn.freebsd.org/changeset/base/192535
>>
>> Log:
>>   Move the M_WAITOK flag in notify() into an M_NOWAIT one in order to match
>>   the behaviour alredy present with the further malloc() call in
>>   devctl_notify().
>>   This fixes a bug in the CAM layer where the camisr handler finished to
>>   call camperiphfree() (and subsequently destroy_dev() resulting in a new
>>   dev notify) while the xpt lock is held.
> This is wrong. You cannot call destroy_dev() while holding any mutex.
> Taking this into account, it makes no sense to use M_NOWAIT in notify().

As long as devctl_notify() also calls M_NOWAIT and if not available
skips "silently" it just does the same thing, I think this approach is
more consistent.

It remains, though, the fact to fix CAM when calling destroy_dev().
Maybe we should add a witness_warn() there?

Thanks,
Attilio


-- 
Peace can only be achieved by understanding - A. Einstein



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