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

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

[Alan Stern]

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@rowland.harvard.edu>

---


 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)
 
 (**********************************)

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

[Paul E. McKenney]

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@rowland.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)
>  
>  (**********************************)
>