linux-kernel - [PATCH v4 12/20] arch_topology: Set thread sibling cpumask only within the cluster

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Date:   Tue, 21 Jun 2022 20:20:26 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     linux-kernel@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Atish Patra <atishp@...shpatra.org>,
        Atish Patra <atishp@...osinc.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Qing Wang <wangqing@...o.com>,
        Rob Herring <robh+dt@...nel.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Ionela Voinescu <ionela.voinescu@....com>,
        Pierre Gondois <pierre.gondois@....com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, Gavin Shan <gshan@...hat.com>
Subject: [PATCH v4 12/20] arch_topology: Set thread sibling cpumask 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 imay result in getting the thread
siblings wrongs as the core identifiers can be same for 2 different CPUs
belonging to 2 different cluster.

So, in order to get the thread sibling cpumasks correct, we need to
update them only if the cores they belong are in the same cluster within
the socket. Let us skip updation of the thread sibling cpumaks if 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.

Reviewed-by: Gavin Shan <gshan@...hat.com>
Tested-by: Gavin Shan <gshan@...hat.com>
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 drivers/base/arch_topology.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index b63cc52e12ce..7a5ff1ea5f00 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -708,15 +708,17 @@ void update_siblings_masks(unsigned int cpuid)
 		if (cpuid_topo->package_id != cpu_topo->package_id)
 			continue;
 
-		if (cpuid_topo->cluster_id == cpu_topo->cluster_id &&
-		    cpuid_topo->cluster_id != -1) {
+		cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
+		cpumask_set_cpu(cpu, &cpuid_topo->core_sibling);
+
+		if (cpuid_topo->cluster_id != cpu_topo->cluster_id)
+			continue;
+
+		if (cpuid_topo->cluster_id != -1) {
 			cpumask_set_cpu(cpu, &cpuid_topo->cluster_sibling);
 			cpumask_set_cpu(cpuid, &cpu_topo->cluster_sibling);
 		}
 
-		cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
-		cpumask_set_cpu(cpu, &cpuid_topo->core_sibling);
-
 		if (cpuid_topo->core_id != cpu_topo->core_id)
 			continue;
 
-- 
2.36.1