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From:   Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
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Cc:     Salil Mehta <salil.mehta@huawei.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        jianyong.wu@arm.com, justin.he@arm.com,
        James Morse <james.morse@arm.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>
Subject: [PATCH 08/21] drivers: base: Implement weak arch_unregister_cpu()
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Sender: Russell King <rmk@armlinux.org.uk>
Date:   Tue, 21 Nov 2023 13:44:31 +0000
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From: James Morse <james.morse@arm.com>

Add arch_unregister_cpu() to allow the ACPI machinery to call
unregister_cpu(). This is enough for arm64, riscv and loongarch, but
needs to be overridden by x86 and ia64 who need to do more work.

CC: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
An open question remains from the RFC v2 posting: should we provide a
__weak stub for !HOTPLUG_CPU as well, since in later patches ACPI may
reference this if the compiler doesn't optimise as we expect?

Changes since v1:
 * Added CONFIG_HOTPLUG_CPU ifdeffery around unregister_cpu
Changes since RFC v2:
 * Move earlier in the series
---
 drivers/base/cpu.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 579064fda97b..58bb86091b34 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -531,7 +531,14 @@ int __weak arch_register_cpu(int cpu)
 {
 	return register_cpu(&per_cpu(cpu_devices, cpu), cpu);
 }
-#endif
+
+#ifdef CONFIG_HOTPLUG_CPU
+void __weak arch_unregister_cpu(int num)
+{
+	unregister_cpu(&per_cpu(cpu_devices, num));
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+#endif /* CONFIG_GENERIC_CPU_DEVICES */
 
 static void __init cpu_dev_register_generic(void)
 {
-- 
2.30.2