linux-kernel - Re: [PATCH 1/3] tools: memory-model: Expand definition of barrier

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Message-ID: <20190620163746.GS26519@linux.ibm.com>
Date:   Thu, 20 Jun 2019 09:37:46 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     LKMM Maintainers -- Akira Yokosawa <akiyks@...il.com>,
        Andrea Parri <andrea.parri@...rulasolutions.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Daniel Lustig <dlustig@...dia.com>,
        David Howells <dhowells@...hat.com>,
        Jade Alglave <j.alglave@....ac.uk>,
        Luc Maranget <luc.maranget@...ia.fr>,
        Nicholas Piggin <npiggin@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will.deacon@....com>,
        Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] tools: memory-model: Expand definition of barrier

On Thu, Jun 20, 2019 at 11:55:36AM -0400, Alan Stern wrote:
> Commit 66be4e66a7f4 ("rcu: locking and unlocking need to always be at
> least barriers") added compiler barriers back into rcu_read_lock() and
> rcu_read_unlock().  Furthermore, srcu_read_lock() and
> srcu_read_unlock() have always contained compiler barriers.
> 
> The Linux Kernel Memory Model ought to know about these barriers.
> This patch adds them into the memory model.
> 
> Signed-off-by: Alan Stern <stern@...land.harvard.edu>

And yes, much easier to understand this way, thank you!

I have queued them and they both diff equal to your previous patch and
give the expected results on the litmus-tests and github tests having
Result tags.

							Thanx, Paul

> ---
> 
> 
>  tools/memory-model/linux-kernel.cat |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> Index: usb-devel/tools/memory-model/linux-kernel.cat
> ===================================================================
> --- usb-devel.orig/tools/memory-model/linux-kernel.cat
> +++ usb-devel/tools/memory-model/linux-kernel.cat
> @@ -47,7 +47,8 @@ let strong-fence = mb | gp
>  let nonrw-fence = strong-fence | po-rel | acq-po
>  let fence = nonrw-fence | wmb | rmb
>  let barrier = fencerel(Barrier | Rmb | Wmb | Mb | Sync-rcu | Sync-srcu |
> -		Before-atomic | After-atomic | Acquire | Release) |
> +		Before-atomic | After-atomic | Acquire | Release |
> +		Rcu-lock | Rcu-unlock | Srcu-lock | Srcu-unlock) |
>  	(po ; [Release]) | ([Acquire] ; po)
>  
>  (**********************************)
>