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Date: Thu, 6 Jun 2024 12:00:22 -0700
From: "Paul E. McKenney" <paulmck@kernel.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrea Parri <parri.andrea@gmail.com>, will@kernel.org,
	peterz@infradead.org, boqun.feng@gmail.com, npiggin@gmail.com,
	dhowells@redhat.com, j.alglave@ucl.ac.uk, luc.maranget@inria.fr,
	akiyks@gmail.com, dlustig@nvidia.com, joel@joelfernandes.org,
	linux-kernel@vger.kernel.org, hernan.poncedeleon@huaweicloud.com,
	jonas.oberhauser@huaweicloud.com
Subject: Re: New locking test for the paulmckrcu/litmus github archive
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On Thu, Jun 06, 2024 at 02:52:02PM -0400, Alan Stern wrote:
> On Thu, Jun 06, 2024 at 10:57:42AM -0700, Paul E. McKenney wrote:
> > On Thu, Jun 06, 2024 at 01:21:28PM -0400, Alan Stern wrote:
> > > Okay.  Don't we already have a litmus test in the archive that really 
> > > does create a deadlock?  Something like: Lock Lock Unlock Unlock, all 
> > > using the same lock variable?
> > 
> > We do have these guys:
> > 
> > auto/C-RR-GR+RR-R+RR-R.litmus
> > auto/C-RR-GR+RR-R.litmus
> > auto/C-RW-GR+RW-R+RW-R.litmus
> > auto/C-RW-GR+RW-R.litmus
> > auto/C-WR-GR+WR-R+WR-R.litmus
> > auto/C-WR-GR+WR-R.litmus
> > auto/C-WW-GR+WW-R+WW-R.litmus
> > auto/C-WW-GR+WW-R.litmus
> > 	A synchronize_rcu() in an RCU read-side critical section.
> > 
> > I added a manual/locked/self-deadlock.litmus, which is shown at the
> > end of this email.  Omitting the nested self-deadlocking acquisition
> > and release gives one state with blank line.  ;-)
> 
> Hah, because there is no "exists" clause and no variables other than the 
> spinlock itself.

;-) ;-) ;-)

> > Or should I add a spin_is_locked() in order to get a non-empty
> > state line?
> 
> It's fine the way it is.

Very good, pushed.

							Thanx, Paul