linux-kernel - [PATCH] driver core / cpu: Check if NUMA node is valid before bringing CPU up

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Date:	Tue, 13 Aug 2013 02:39:30 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Toshi Kani <toshi.kani@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Tang Chen <tangchen@...fujitsu.com>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	rafael.j.wysocki@...el.com, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, Wen Congyang <wency@...fujitsu.com>
Subject: [PATCH] driver core / cpu: Check if NUMA node is valid before bringing CPU up

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

There is a potential race condition between cpu_subsys_online()
and either acpi_processor_remove() or remove_memory() that execute
try_offline_node().  Namely, it is possible that cpu_subsys_online()
will run right after the CPUs NUMA node has been put offline and
cpu_to_node() executed by it will return NUMA_NO_NODE (-1).  In
that case the CPU is gone and it doesn't make sense to call cpu_up()
for it, so make cpu_subsys_online() return -ENODEV then.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Acked-by: Toshi Kani <toshi.kani@...com>
---

Hi Greg,

Can you please kindly queue up this one for 3.12?

I've added the Toshi's ACK as he said it looked good to him. :-)

Thanks,
Rafael

---
 drivers/base/cpu.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Index: linux-pm/drivers/base/cpu.c
===================================================================
--- linux-pm.orig/drivers/base/cpu.c
+++ linux-pm/drivers/base/cpu.c
@@ -43,11 +43,14 @@ static int __ref cpu_subsys_online(struc
 	struct cpu *cpu = container_of(dev, struct cpu, dev);
 	int cpuid = dev->id;
 	int from_nid, to_nid;
-	int ret;
+	int ret = -ENODEV;
 
 	cpu_hotplug_driver_lock();
 
 	from_nid = cpu_to_node(cpuid);
+	if (from_nid == NUMA_NO_NODE)
+		goto out;
+
 	ret = cpu_up(cpuid);
 	/*
 	 * When hot adding memory to memoryless node and enabling a cpu
@@ -57,6 +60,7 @@ static int __ref cpu_subsys_online(struc
 	if (from_nid != to_nid)
 		change_cpu_under_node(cpu, from_nid, to_nid);
 
+ out:
 	cpu_hotplug_driver_unlock();
 	return ret;
 }

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