linux-kernel - [tip: sched/core] sched/topology: Propagate SMT flags when removing degenerate domain

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Date:   Wed, 10 May 2023 13:49:09 -0000
From:   "tip-bot2 for Tim C Chen" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/topology: Propagate SMT flags when removing
 degenerate domain

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     bf2dc42d6beb890c995b8b09f881ef1b37259107
Gitweb:        https://git.kernel.org/tip/bf2dc42d6beb890c995b8b09f881ef1b37259107
Author:        Tim C Chen <tim.c.chen@...ux.intel.com>
AuthorDate:    Thu, 04 May 2023 09:09:51 -07:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 08 May 2023 10:58:39 +02:00

sched/topology: Propagate SMT flags when removing degenerate domain

When a degenerate cluster domain for core with SMT CPUs is removed,
the SD_SHARE_CPUCAPACITY flag in the local child sched group was not
propagated to the new parent.  We need this flag to properly determine
whether the local sched group is SMT.  Set the flag in the local
child sched group of the new parent sched domain.

Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Link: https://lkml.kernel.org/r/73cf0959eafa53c02e7ef6bf805d751d9190e55d.1683156492.git.tim.c.chen@linux.intel.com
---
 kernel/sched/topology.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 6682535..ca44722 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -719,8 +719,13 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
 
 		if (sd_parent_degenerate(tmp, parent)) {
 			tmp->parent = parent->parent;
-			if (parent->parent)
+
+			if (parent->parent) {
 				parent->parent->child = tmp;
+				if (tmp->flags & SD_SHARE_CPUCAPACITY)
+					parent->parent->groups->flags |= SD_SHARE_CPUCAPACITY;
+			}
+
 			/*
 			 * Transfer SD_PREFER_SIBLING down in case of a
 			 * degenerate parent; the spans match for this