linux-kernel - Re: [PATCH 1/3] tools: memory-model: Prepare for data-race detection

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Message-Id: <20190424082231.GF3923@linux.ibm.com>
Date:   Wed, 24 Apr 2019 01:22:31 -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>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH 1/3] tools: memory-model: Prepare for data-race detection

On Mon, Apr 22, 2019 at 12:17:45PM -0400, Alan Stern wrote:
> This patch makes some slight alterations to linux-kernel.cat in
> preparation for adding support for data-race detection to the
> Linux-Kernel Memory Model.
> 
> 	The definitions of relations involved in Acquire, Release, and
> 	unlock-lock ordering are moved up earlier in the source file.
> 
> 	The rmb relation is factored through the new R4rmb class: the
> 	class of reads to which rmb will apply.
> 
> 	The definition of the fence relation is moved earlier, and it
> 	is split up into read- and write-fences (rmb and wmb) and all
> 	the others.
> 
> This should not make any functional changes.
> 
> Signed-off-by: Alan Stern <stern@...land.harvard.edu>

Thank you, Alan, I have queued all three onto -rcu for review and testing.
FYI, I rebased my smp_mb__{before,after}_atomic() patch on top of yours
to avoid the conflict.

Which demonstrates non-commutativity of patches.  Your patches conflict
with mine, but mine does not conflict with yours.  ;-)

							Thanx, Paul

> ---
> 
> 
>  tools/memory-model/linux-kernel.cat |   16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> 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
> @@ -26,8 +26,14 @@ include "lock.cat"
>  (* Basic relations *)
>  (*******************)
>  
> +(* Release Acquire *)
> +let acq-po = [Acquire] ; po ; [M]
> +let po-rel = [M] ; po ; [Release]
> +let po-unlock-rf-lock-po = po ; [UL] ; rf ; [LKR] ; po
> +
>  (* Fences *)
> -let rmb = [R \ Noreturn] ; fencerel(Rmb) ; [R \ Noreturn]
> +let R4rmb = R \ Noreturn	(* Reads for which rmb works *)
> +let rmb = [R4rmb] ; fencerel(Rmb) ; [R4rmb]
>  let wmb = [W] ; fencerel(Wmb) ; [W]
>  let mb = ([M] ; fencerel(Mb) ; [M]) |
>  	([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) |
> @@ -36,13 +42,10 @@ let mb = ([M] ; fencerel(Mb) ; [M]) |
>  	([M] ; po ; [UL] ; (co | po) ; [LKW] ;
>  		fencerel(After-unlock-lock) ; [M])
>  let gp = po ; [Sync-rcu | Sync-srcu] ; po?
> -
>  let strong-fence = mb | gp
>  
> -(* Release Acquire *)
> -let acq-po = [Acquire] ; po ; [M]
> -let po-rel = [M] ; po ; [Release]
> -let po-unlock-rf-lock-po = po ; [UL] ; rf ; [LKR] ; po
> +let nonrw-fence = strong-fence | po-rel | acq-po
> +let fence = nonrw-fence | wmb | rmb
>  
>  (**********************************)
>  (* Fundamental coherence ordering *)
> @@ -65,7 +68,6 @@ let rwdep = (dep | ctrl) ; [W]
>  let overwrite = co | fr
>  let to-w = rwdep | (overwrite & int)
>  let to-r = addr | (dep ; rfi)
> -let fence = strong-fence | wmb | po-rel | rmb | acq-po
>  let ppo = to-r | to-w | fence | (po-unlock-rf-lock-po & int)
>  
>  (* Propagation: Ordering from release operations and strong fences. *)
> 
>