From: Jonas Oberhauser Date: Mon, 30 Sep 2024 10:57:08 +0000 (+0200) Subject: tools/memory-model: Define effect of Mb tags on RMWs in tools/... X-Git-Tag: v6.15-rc1~225^2~4 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=29279349a566232057f52392d1a8af91772de7e1;p=thirdparty%2Fkernel%2Flinux.git tools/memory-model: Define effect of Mb tags on RMWs in tools/... 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 Suggested-by: Alan Stern Signed-off-by: Jonas Oberhauser Signed-off-by: Paul E. McKenney Reviewed-by: Boqun Feng Tested-by: Boqun Feng --- diff --git a/tools/memory-model/linux-kernel.cat b/tools/memory-model/linux-kernel.cat index adf3c4f412296..d7e7bf13c831b 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]) |