linux-kernel - [ACPIHP PATCH part4 3/9] ACPIHP/processor: protect accesses to device->driver

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Date:	Sun,  4 Nov 2012 23:23:56 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	"Rafael J . Wysocki" <rjw@...k.pl>,
	Yinghai Lu <yinghai@...nel.org>,
	Tony Luck <tony.luck@...el.com>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	Taku Izumi <izumi.taku@...fujitsu.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Jiang Liu <jiang.liu@...wei.com>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Huang Ying <ying.huang@...el.com>,
	Bob Moore <robert.moore@...el.com>,
	Len Brown <lenb@...nel.org>,
	"Srivatsa S . Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Yijing Wang <wangyijing@...wei.com>,
	Hanjun Guo <guohanjun@...wei.com>,
	Jiang Liu <liuj97@...il.com>, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-mm@...ck.org
Subject: [ACPIHP PATCH part4 3/9] ACPIHP/processor: protect accesses to device->driver_data

CPU hotplug notification handler acpi_cpu_soft_notify() and driver
unbind method acpi_processor_remove() may be concurrently called.
acpi_cpu_soft_notify() will access device->driver_data, but that
data structure may be destroyed by acpi_processor_remove().

On the other hand, acpi_cpu_soft_notify() is always called under
protection of get_online_cpus(), so use get_online_cpus() to serialize
all accesses and modifications to device->driver_data.

Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
---
 drivers/acpi/processor_driver.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index 28add34..7d6d794 100644
--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -616,6 +616,8 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
 		return 0;
 	BUG_ON((pr->id >= nr_cpu_ids) || (pr->id < 0));
 
+	/* block CPU online/offline operations */
+	get_online_cpus();
 	result = acpi_processor_link(device, pr);
 	if (result)
 		goto err_unlock;
@@ -624,6 +626,7 @@ static int __cpuinit acpi_processor_add(struct acpi_device *device)
 		if (result)
 			goto err_unlink;
 	}
+	put_online_cpus();
 
 	return 0;
 
@@ -654,8 +657,10 @@ static int acpi_processor_remove(struct acpi_device *device, int type)
 			return -EINVAL;
 	}
 
+	get_online_cpus();
 	acpi_processor_stop(device, pr);
 	acpi_processor_unlink(device, pr);
+	put_online_cpus();
 
 free:
 	device->driver_data = NULL;
-- 
1.7.9.5

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