linux-kernel - [PATCH 2/4] arch_topology: Set thread and core siblings only within the cluster

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Message-Id: <20220513095559.1034633-3-sudeep.holla@arm.com>
Date:   Fri, 13 May 2022 10:55:57 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Atish Patra <atishp@...shpatra.org>,
        Atish Patra <atishp@...osinc.com>, linux-kernel@...r.kernel.org
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Atish Patra <atish.patra@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Qing Wang <wangqing@...o.com>
Subject: [PATCH 2/4] arch_topology: Set thread and core siblings only within the cluster

Currently the cluster identifier is not set on the DT based platforms.
The reset or default value is -1 for all the CPUs. Once we assign the
cluster identifier values correctly that may result in getting the core
siblings wrongs as the core identifiers can be same for 2 different CPUs
belonging to 2 different cluster.

So, in order to get the core and thread sibling masks correct, we need to
update them only if they belong to same cluster within the socket. Let
us skip updation of the thread and core sibling cpumaks if the socket
and the cluster identifier doesn't match.

This change won't affect even if the cluster identifiers are not set
currently but will avoid any breakage once we set the same correctly.

Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 drivers/base/arch_topology.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index 44f733b365cc..5812428253d8 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -694,11 +694,11 @@ void update_siblings_masks(unsigned int cpuid)
 			cpumask_set_cpu(cpuid, &cpu_topo->llc_sibling);
 		}

-		if (cpuid_topo->package_id != cpu_topo->package_id)
+		if (cpuid_topo->package_id != cpu_topo->package_id ||
+		    cpuid_topo->cluster_id != cpu_topo->cluster_id)
 			continue;

-		if (cpuid_topo->cluster_id == cpu_topo->cluster_id &&
-		    cpuid_topo->cluster_id != -1) {
+		if (cpuid_topo->cluster_id != -1) {
 			cpumask_set_cpu(cpu, &cpuid_topo->cluster_sibling);
 			cpumask_set_cpu(cpuid, &cpu_topo->cluster_sibling);
 		}
-- 
2.36.1