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Date: Tue, 19 Aug 2008 11:16:50 -0700
From: Julian Elischer <julian@elischer.org>
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To: Ed Maste <emaste@freebsd.org>
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Cc: freebsd-hackers@freebsd.org
Subject: Re: Acquiring a mtx after an sx lock
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Ed Maste wrote:
> On Mon, Aug 18, 2008 at 11:38:40AM -0700, Julian Elischer wrote:
> 
>>> Ed Maste wrote:
>>>> Ahh, it seems ups' commit of rmlocks changed the "You have: sx_lock,
>>>> You want: Slp_mtx" case from no to ok (in r173444).
>> Ignore me.. I was reading the table backwards.. of course if you have 
>> an sx you can still take out a mutex, but not visa versa.
> 
> Yep, and ups' r173444 change didn't affect this at all, it just
> corrected the table.
> 
> If I don't hear otherwise I'll merge the changes to the table to 7
> sometime soon:
> 
>   You have:  You want: Spin_mtx Slp_mtx sx_lock rw_lock sleep
> - SPIN mutex           ok       no      no      no      no-3
> + SPIN mutex           ok-1     no      no      no      no-3
>   Sleep mutex          ok       ok-1    no      ok      no-3
> - sx_lock              ok       no      ok-2    no      ok-4
> + sx_lock              ok       ok      ok-2    ok      ok-4
>   rw_lock              ok       ok      no      ok-2    no-3
> 
> Have SPIN / want SPIN adds the "Recursion is defined per lock" footnote.
> 
> Have sx / want Slp & have sx / want rw change from no to ok.

I agree

> 
> - Ed
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