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tools/memory-model: Change definition of rcu-fence

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The rcu-fence relation in the Linux Kernel Memory Model is not well
named.  It doesn't act like any other fence relation, in that it does
not relate events before a fence to events after that fence.  All it
does is relate certain RCU events to one another (those that are
ordered by the RCU Guarantee); this induces an actual
strong-fence-like relation linking events preceding the first RCU
event to those following the second.

This patch renames rcu-fence, now called rcu-order.  It adds a new
definition of rcu-fence, something which should have been present all
along because it is used in the rb relation.  And it modifies the
fence and strong-fence relations by making them incorporate the new
rcu-fence.

As a result of this change, there is no longer any need to define
full-fence in the section for detecting data races.  It can simply be
replaced by the updated strong-fence relation.

This change should have no effect on the operation of the memory model.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
This commit is contained in:
Alan Stern 2019-06-20 11:55:46 -04:00 committed by Paul E. McKenney
parent f9de417121
commit 15aa25cbf0
1 changed files with 13 additions and 10 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

23
tools/memory-model/linux-kernel.cat
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@ -122,24 +122,28 @@ let rcu-link = po? ; hb* ; pb* ; prop ; po
(*
* Any sequence containing at least as many grace periods as RCU read-side
* critical sections (joined by rcu-link) acts as a generalized strong fence.
* critical sections (joined by rcu-link) induces order like a generalized
* inter-CPU strong fence.
* Likewise for SRCU grace periods and read-side critical sections, provided
* the synchronize_srcu() and srcu_read_[un]lock() calls refer to the same
* struct srcu_struct location.
*)
let rec rcu-fence = rcu-gp | srcu-gp |
let rec rcu-order = rcu-gp | srcu-gp |
(rcu-gp ; rcu-link ; rcu-rscsi) |
((srcu-gp ; rcu-link ; srcu-rscsi) & loc) |
(rcu-rscsi ; rcu-link ; rcu-gp) |
((srcu-rscsi ; rcu-link ; srcu-gp) & loc) |
(rcu-gp ; rcu-link ; rcu-fence ; rcu-link ; rcu-rscsi) |
((srcu-gp ; rcu-link ; rcu-fence ; rcu-link ; srcu-rscsi) & loc) |
(rcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; rcu-gp) |
((srcu-rscsi ; rcu-link ; rcu-fence ; rcu-link ; srcu-gp) & loc) |
(rcu-fence ; rcu-link ; rcu-fence)
(rcu-gp ; rcu-link ; rcu-order ; rcu-link ; rcu-rscsi) |
((srcu-gp ; rcu-link ; rcu-order ; rcu-link ; srcu-rscsi) & loc) |
(rcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; rcu-gp) |
((srcu-rscsi ; rcu-link ; rcu-order ; rcu-link ; srcu-gp) & loc) |
(rcu-order ; rcu-link ; rcu-order)
let rcu-fence = po ; rcu-order ; po?
let fence = fence | rcu-fence
let strong-fence = strong-fence | rcu-fence
(* rb orders instructions just as pb does *)
let rb = prop ; po ; rcu-fence ; po? ; hb* ; pb* ; [Marked]
let rb = prop ; rcu-fence ; hb* ; pb* ; [Marked]
irreflexive rb as rcu
@ -163,9 +167,8 @@ flag ~empty mixed-accesses as mixed-accesses
(* Executes-before and visibility *)
let xbstar = (hb | pb | rb)*
let full-fence = strong-fence | (po ; rcu-fence ; po?)
let vis = cumul-fence* ; rfe? ; [Marked] ;
((full-fence ; [Marked] ; xbstar) | (xbstar & int))
((strong-fence ; [Marked] ; xbstar) | (xbstar & int))
(* Boundaries for lifetimes of plain accesses *)
let w-pre-bounded = [Marked] ; (addr | fence)?