linux-kernel - [PATCH 2/2] powerpc/topology: Check if a core is online

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Date: Thu, 13 Jun 2024 00:20:38 +0530
From: "Nysal Jan K.A." <nysal@...ux.ibm.com>
To: Michael Ellerman <mpe@...erman.id.au>,
        Thomas Gleixner <tglx@...utronix.de>
Cc: Tyrel Datwyler <tyreld@...ux.ibm.com>, Michal Suchanek <msuchanek@...e.de>,
        "Nysal Jan K.A" <nysal@...ux.ibm.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] powerpc/topology: Check if a core is online

From: "Nysal Jan K.A" <nysal@...ux.ibm.com>

topology_is_core_online() checks if the core a CPU belongs to
is online. The core is online if at least one of the sibling
CPUs is online. The first CPU of an online core is also online
in the common case, so this should be fairly quick.

Signed-off-by: Nysal Jan K.A <nysal@...ux.ibm.com>
---
 arch/powerpc/include/asm/topology.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h
index f4e6f2dd04b7..16bacfe8c7a2 100644
--- a/arch/powerpc/include/asm/topology.h
+++ b/arch/powerpc/include/asm/topology.h
@@ -145,6 +145,7 @@ static inline int cpu_to_coregroup_id(int cpu)
 
 #ifdef CONFIG_HOTPLUG_SMT
 #include <linux/cpu_smt.h>
+#include <linux/cpumask.h>
 #include <asm/cputhreads.h>
 
 static inline bool topology_is_primary_thread(unsigned int cpu)
@@ -156,6 +157,18 @@ static inline bool topology_smt_thread_allowed(unsigned int cpu)
 {
 	return cpu_thread_in_core(cpu) < cpu_smt_num_threads;
 }
+
+#define topology_is_core_online topology_is_core_online
+static inline bool topology_is_core_online(unsigned int cpu)
+{
+	int i, first_cpu = cpu_first_thread_sibling(cpu);
+
+	for (i = first_cpu; i < first_cpu + threads_per_core; ++i) {
+		if (cpu_online(i))
+			return true;
+	}
+	return false;
+}
 #endif
 
 #endif /* __KERNEL__ */
-- 
2.35.3