linux-kernel - [RFC PATCH v1 15/22] PCI/eeepc: use PCI bus lock to avoid race conditions

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Date:	Wed,  8 Aug 2012 00:10:55 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Don Dutile <ddutile@...hat.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
Cc:	Jiang Liu <jiang.liu@...wei.com>,
	Taku Izumi <izumi.taku@...fujitsu.com>,
	"Rafael J . Wysocki" <rjw@...k.pl>,
	Yijing Wang <wangyijing@...wei.com>,
	Xinwei Hu <huxinwei@...wei.com>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, Jiang Liu <liuj97@...il.com>
Subject: [RFC PATCH v1 15/22] PCI/eeepc: use PCI bus lock to avoid race conditions

This patch uses PCI bus lock mechanism to avoid race conditions when doing
PCI device hotplug through eeepc driver. It also fixes a PCI device reference
count leakage issue because acpi_get_pci_dev() holds a reference to the
device returned.

Signed-off-by: Jiang Liu <liuj97@...il.com>
---
 drivers/platform/x86/eeepc-laptop.c |   20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/platform/x86/eeepc-laptop.c b/drivers/platform/x86/eeepc-laptop.c
index dab91b4..25c4176 100644
--- a/drivers/platform/x86/eeepc-laptop.c
+++ b/drivers/platform/x86/eeepc-laptop.c
@@ -606,16 +606,16 @@ static void eeepc_rfkill_hotplug(struct eeepc_laptop *eeepc, acpi_handle handle)
 			goto out_unlock;
 		}
 
-		bus = port->subordinate;
+		bus = pci_lock_subordinate(port, PCI_BUS_STATE_WORKING);
 
 		if (!bus) {
 			pr_warn("Unable to find PCI bus 1?\n");
-			goto out_unlock;
+			goto out_put_dev;
 		}
 
 		if (pci_bus_read_config_dword(bus, 0, PCI_VENDOR_ID, &l)) {
 			pr_err("Unable to read PCI config space?\n");
-			goto out_unlock;
+			goto out_unlock_bus;
 		}
 
 		absent = (l == 0xffffffff);
@@ -627,7 +627,7 @@ static void eeepc_rfkill_hotplug(struct eeepc_laptop *eeepc, acpi_handle handle)
 				absent ? "absent" : "present");
 			pr_warn("skipped wireless hotplug as probably "
 				"inappropriate for this model\n");
-			goto out_unlock;
+			goto out_unlock_bus;
 		}
 
 		if (!blocked) {
@@ -635,7 +635,7 @@ static void eeepc_rfkill_hotplug(struct eeepc_laptop *eeepc, acpi_handle handle)
 			if (dev) {
 				/* Device already present */
 				pci_dev_put(dev);
-				goto out_unlock;
+				goto out_unlock_bus;
 			}
 			dev = pci_scan_single_device(bus, 0);
 			if (dev) {
@@ -650,6 +650,11 @@ static void eeepc_rfkill_hotplug(struct eeepc_laptop *eeepc, acpi_handle handle)
 				pci_dev_put(dev);
 			}
 		}
+
+out_unlock_bus:
+		pci_bus_unlock(bus);
+out_put_dev:
+		pci_dev_put(port);
 	}
 
 out_unlock:
@@ -757,7 +762,7 @@ static struct hotplug_slot_ops eeepc_hotplug_slot_ops = {
 static int eeepc_setup_pci_hotplug(struct eeepc_laptop *eeepc)
 {
 	int ret = -ENOMEM;
-	struct pci_bus *bus = pci_find_bus(0, 1);
+	struct pci_bus *bus = pci_get_bus(0, 1);
 
 	if (!bus) {
 		pr_err("Unable to find wifi PCI bus\n");
@@ -785,6 +790,8 @@ static int eeepc_setup_pci_hotplug(struct eeepc_laptop *eeepc)
 		goto error_register;
 	}
 
+	pci_bus_put(bus);
+
 	return 0;
 
 error_register:
@@ -793,6 +800,7 @@ error_info:
 	kfree(eeepc->hotplug_slot);
 	eeepc->hotplug_slot = NULL;
 error_slot:
+	pci_bus_put(bus);
 	return ret;
 }
 
-- 
1.7.9.5

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