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Date:      Tue, 19 Aug 2008 11:26:07 -0400
From:      Ed Maste <emaste@freebsd.org>
To:        Julian Elischer <julian@elischer.org>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: Acquiring a mtx after an sx lock
Message-ID:  <20080819152607.GA44331@sandvine.com>
In-Reply-To: <48A9C1B0.5010805@elischer.org>
References:  <bc2d970808180814ue926d43s7966b36ffa3c9699@mail.gmail.com> <200808181754.18812.max@love2party.net> <bc2d970808180902h1ded9bcbp494d276ede0eeed@mail.gmail.com> <20080818162411.GA77460@sandvine.com> <48A9BFED.604@elischer.org> <48A9C1B0.5010805@elischer.org>

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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.

- Ed



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