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tools/memory-model: Define effect of Mb tags on RMWs in tools/...

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Herd7 transforms successful RMW with Mb tags by inserting smp_mb() fences
around them. We emulate this by considering imaginary po-edges before the
RMW read and before the RMW write, and extending the smp_mb() ordering
rule, which currently only applies to real po edges that would be found
around a really inserted smp_mb(), also to cases of the only imagined po
edges.

Reported-by: Viktor Vafeiadis <viktor@mpi-sws.org>
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
This commit is contained in:
Jonas Oberhauser 2024-09-30 12:57:08 +02:00 committed by Paul E. McKenney
parent 93bde3aa88
commit a73d299a22
1 changed files with 10 additions and 0 deletions
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tools/memory-model/linux-kernel.cat
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@ -34,6 +34,16 @@ 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]) |
(*
* full-barrier RMWs (successful cmpxchg(), xchg(), etc.) act as
* though there were enclosed by smp_mb().
* The effect of these virtual smp_mb() is formalized by adding
* Mb tags to the read and write of the operation, and providing
* the same ordering as though there were additional po edges
* between the Mb tag and the read resp. write.
*)
([M] ; po ; [Mb & R]) |
([Mb & W] ; po ; [M]) |
([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) |
([M] ; po? ; [RMW] ; fencerel(After-atomic) ; [M]) |
([M] ; po? ; [LKW] ; fencerel(After-spinlock) ; [M]) |