From: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>
To: paulmck@kernel.org
Cc: stern@rowland.harvard.edu, parri.andrea@gmail.com,
will@kernel.org, peterz@infradead.org, boqun.feng@gmail.com,
npiggin@gmail.com, dhowells@redhat.com, j.alglave@ucl.ac.uk,
luc.maranget@inria.fr, akiyks@gmail.com, dlustig@nvidia.com,
joel@joelfernandes.org, urezki@gmail.com,
quic_neeraju@quicinc.com, frederic@kernel.org,
linux-kernel@vger.kernel.org, lkmm@lists.linux.dev,
hernan.poncedeleon@huaweicloud.com,
Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>,
Viktor Vafeiadis <viktor@mpi-sws.org>
Subject: [PATCH v3 3/5] tools/memory-model: Define effect of Mb tags on RMWs in tools/...
Date: Thu, 19 Sep 2024 15:06:32 +0200 [thread overview]
Message-ID: <20240919130634.298181-4-jonas.oberhauser@huaweicloud.com> (raw)
In-Reply-To: <20240919130634.298181-1-jonas.oberhauser@huaweicloud.com>
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>
---
tools/memory-model/linux-kernel.cat | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/tools/memory-model/linux-kernel.cat b/tools/memory-model/linux-kernel.cat
index adf3c4f41229..d7e7bf13c831 100644
--- a/tools/memory-model/linux-kernel.cat
+++ b/tools/memory-model/linux-kernel.cat
@@ -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]) |
--
2.34.1
next prev parent reply other threads:[~2024-09-19 13:07 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-19 13:06 [PATCH v3 0/5] tools/memory-model: Define more of LKMM in tools/memory-model Jonas Oberhauser
2024-09-19 13:06 ` [PATCH v3 1/5] tools/memory-model: Legitimize current use of tags in LKMM macros Jonas Oberhauser
2024-09-19 13:06 ` [PATCH v3 2/5] tools/memory-model: Define applicable tags on operation in tools/ Jonas Oberhauser
2024-09-19 13:06 ` Jonas Oberhauser [this message]
2024-09-19 13:06 ` [PATCH v3 4/5] tools/memory-model: Switch to softcoded herd7 tags Jonas Oberhauser
2024-09-20 12:23 ` Hernan Ponce de Leon
2024-09-21 2:44 ` Akira Yokosawa
2024-09-21 7:39 ` Jonas Oberhauser
2024-09-21 11:28 ` Akira Yokosawa
2024-09-19 13:06 ` [PATCH v3 5/5] tools/memory-model: Distinguish between syntactic and semantic tags Jonas Oberhauser
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