linux-kernel - [Patch v1] ACPI, x86: fix bug in associating hot-added CPUs with corresponding NUMA node

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Date:	Mon, 20 Jan 2014 10:31:54 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Toshi Kani <toshi.kani@...com>,
	Yinghai Lu <yinghai@...nel.org>,
	Yijing Wang <wangyijing@...wei.com>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Cc:	Jiang Liu <jiang.liu@...ux.intel.com>, linux-acpi@...r.kernel.org,
	linux-hotplug@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: [Patch v1] ACPI, x86: fix bug in associating hot-added CPUs with corresponding NUMA node

Current ACPI cpu hotplug driver fails to associate hot-added CPUs with
corresponding NUMA node when doing socket online. The code path to
associate CPU with NUMA node is as below:
acpi_processor_add()
    ->acpi_processor_get_info()
	->acpi_processor_hotadd_init()
	    ->acpi_map_lsapic()
		->_acpi_map_lsapic()
		    ->acpi_map_cpu2node()
cpu_subsys_online()
    ->try_online_node()
	->node_set_online()

When doing socket online, a new NUMA node is introduced in addition to
hot-added CPU and memory device. And the new NUMA node is marked as
online when onlining hot-added CPUs through sysfs interface
/sys/devices/system/cpu/cpuxx/online.

On the other hand, acpi_map_cpu2node() will only build the CPU to node
map if corresponding NUMA node is already online, so it always fails
to associate hot-added CPUs with corresponding NUMA node because the
NUMA node is still in offline state.

For the fix, we could safely remove the "node_online(node)" check in
function acpi_map_cpu2node() because it's only called for hot-added CPUs
by acpi_processor_hotadd_init().

Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
---
 arch/x86/kernel/acpi/boot.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 6c0b43b..7625de9 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -614,10 +614,10 @@ static void acpi_map_cpu2node(acpi_handle handle, int cpu, int physid)
 	int nid;
 
 	nid = acpi_get_node(handle);
-	if (nid == -1 || !node_online(nid))
-		return;
-	set_apicid_to_node(physid, nid);
-	numa_set_node(cpu, nid);
+	if (nid != -1) {
+		set_apicid_to_node(physid, nid);
+		numa_set_node(cpu, nid);
+	}
 #endif
 }
 
-- 
1.7.10.4

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