linux-kernel - [RFC PATCH v2, part3 05/11] PCI: enhance PCI core logic to support PCI bus lock

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Date:	Thu, 16 May 2013 23:50:53 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>
Cc:	Jiang Liu <jiang.liu@...wei.com>,
	"Rafael J . Wysocki" <rjw@...k.pl>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Gu Zheng <guz.fnst@...fujitsu.com>,
	Toshi Kani <toshi.kani@...com>,
	Myron Stowe <myron.stowe@...hat.com>,
	Yijing Wang <wangyijing@...wei.com>,
	Jiang Liu <liuj97@...il.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH v2, part3 05/11] PCI: enhance PCI core logic to support PCI bus lock

Every new PCI bus will be created with the PCI_BUS_STATE_LOCK bit set,
so a typical PCI device hot-add flow is:
	pci_bus_lock(parent, PCI_BUS_STATE_STARTED, true);
	pci_scan_slot(parent, PCI_DEVFN(0, 0));
	pci_bus_add_devices(parent);
	pci_bus_unlock(parent, true);	// recursively unlock all PCI
					// buses, including new PCI buses

This patch also changes behaviors of interfaces to create PCI root buses:
	pci_create_root_bus(): return with new PCI root bus locked
	pci_scan_bus_parented(): return with new PCI root bus locked
	pci_scan_root_bus(): return with new PCI root bus unlocked
	pci_scan_bus(): return with new PCI root bus unlocked

pci_scan_bus_parented() has already been marked as __deprecated and
all in-tree callers have been converted to use other interfaces.
So following-on patches will enhance callers of pci_create_root_bus()
to unlock returned root buses.

Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
Cc: Yinghai Lu <yinghai@...nel.org>
Cc: linux-pci@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
---
 drivers/pci/hotplug-pci.c |  4 ++++
 drivers/pci/probe.c       | 18 ++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/drivers/pci/hotplug-pci.c b/drivers/pci/hotplug-pci.c
index 18533ed..8faa3c2 100644
--- a/drivers/pci/hotplug-pci.c
+++ b/drivers/pci/hotplug-pci.c
@@ -10,6 +10,10 @@ int __ref pci_hp_add_bridge(struct pci_dev *dev)
 	int pass, busnr, start = parent->busn_res.start;
 	int end = parent->busn_res.end;
 
+	BUG_ON(!pci_bus_is_locked(parent));
+	if (pci_bus_get_state(parent) > PCI_BUS_STATE_STARTED)
+		return 0;
+
 	for (busnr = start; busnr <= end; busnr++) {
 		if (!pci_bus_exists(pci_domain_nr(parent), busnr))
 			break;
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 9fcf3a3..0ddf5b8 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -745,6 +745,10 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
 	u8 primary, secondary, subordinate;
 	int broken = 0;
 
+	BUG_ON(!pci_bus_is_locked(bus));
+	if (pci_bus_get_state(bus) > PCI_BUS_STATE_STARTED)
+		return max;
+
 	pci_read_config_dword(dev, PCI_PRIMARY_BUS, &buses);
 	primary = buses & 0xFF;
 	secondary = (buses >> 8) & 0xFF;
@@ -799,6 +803,8 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
 			pci_bus_insert_busn_res(child, secondary, subordinate);
 			child->bridge_ctl = bctl;
 			pci_bus_get(child);
+		} else {
+			BUG_ON(!pci_bus_is_locked(child));
 		}
 
 		cmax = pci_scan_child_bus(child);
@@ -837,6 +843,8 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
 				goto out;
 			pci_bus_insert_busn_res(child, max, 0xff);
 			pci_bus_get(child);
+		} else {
+			BUG_ON(!pci_bus_is_locked(child));
 		}
 		buses = (buses & 0xff000000)
 		      | ((unsigned int)(child->primary)     <<  0)
@@ -1322,6 +1330,7 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
 {
 	int ret;
 
+	BUG_ON(!pci_bus_is_locked(bus));
 	device_initialize(&dev->dev);
 	dev->dev.release = pci_release_dev;
 
@@ -1369,6 +1378,10 @@ struct pci_dev *__ref pci_scan_single_device(struct pci_bus *bus, int devfn)
 {
 	struct pci_dev *dev;
 
+	BUG_ON(!pci_bus_is_locked(bus));
+	if (pci_bus_get_state(bus) > PCI_BUS_STATE_STARTED)
+		return NULL;
+
 	dev = pci_get_slot(bus, devfn);
 	if (dev) {
 		pci_dev_put(dev);
@@ -1624,6 +1637,8 @@ unsigned int pci_scan_child_bus(struct pci_bus *bus)
 	unsigned int devfn, pass, max = bus->busn_res.start;
 	struct pci_dev *dev;
 
+	BUG_ON(!pci_bus_is_locked(bus));
+	BUG_ON(pci_bus_get_state(bus) > PCI_BUS_STATE_STARTED);
 	dev_dbg(&bus->dev, "scanning bus\n");
 
 	/* Go find them, Rover! */
@@ -1872,6 +1887,8 @@ struct pci_bus *pci_scan_root_bus(struct device *parent, int bus,
 		pci_bus_update_busn_res_end(b, max);
 
 	pci_bus_add_devices(b);
+	pci_bus_unlock(b, true);
+
 	return b;
 }
 EXPORT_SYMBOL(pci_scan_root_bus);
@@ -1908,6 +1925,7 @@ struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops,
 	if (b) {
 		pci_scan_child_bus(b);
 		pci_bus_add_devices(b);
+		pci_bus_unlock(b, true);
 	} else {
 		pci_free_resource_list(&resources);
 	}
-- 
1.8.1.2

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