PCI: Add global pci_lock_rescan_remove()

There are multiple PCI device addition and removal code paths that may be
run concurrently with the generic PCI bus rescan and device removal that
can be triggered via sysfs.  If that happens, it may lead to multiple
different, potentially dangerous race conditions.

The most straightforward way to address those problems is to run
the code in question under the same lock that is used by the
generic rescan/remove code in pci-sysfs.c.  To prepare for those
changes, move the definition of the global PCI remove/rescan lock
to probe.c and provide global wrappers, pci_lock_rescan_remove()
and pci_unlock_rescan_remove(), allowing drivers to manipulate
that lock.  Also provide pci_stop_and_remove_bus_device_locked()
for the callers of pci_stop_and_remove_bus_device() who only need
to hold the rescan/remove lock around it.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index c86c8638d3c4..04796c056d12 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2024,6 +2024,24 @@ EXPORT_SYMBOL(pci_scan_slot);
 EXPORT_SYMBOL(pci_scan_bridge);
 EXPORT_SYMBOL_GPL(pci_scan_child_bus);
 
+/*
+ * pci_rescan_bus(), pci_rescan_bus_bridge_resize() and PCI device removal
+ * routines should always be executed under this mutex.
+ */
+static DEFINE_MUTEX(pci_rescan_remove_lock);
+
+void pci_lock_rescan_remove(void)
+{
+	mutex_lock(&pci_rescan_remove_lock);
+}
+EXPORT_SYMBOL_GPL(pci_lock_rescan_remove);
+
+void pci_unlock_rescan_remove(void)
+{
+	mutex_unlock(&pci_rescan_remove_lock);
+}
+EXPORT_SYMBOL_GPL(pci_unlock_rescan_remove);
+
 static int __init pci_sort_bf_cmp(const struct device *d_a, const struct device *d_b)
 {
 	const struct pci_dev *a = to_pci_dev(d_a);