linux-kernel - [PATCH v2 2/13] ACPI / hotplug / PCI: Move PCI rescan-remove locking to hotplug

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Date:	Sun, 02 Feb 2014 01:22:06 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>, Aaron Lu <aaron.lu@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: [PATCH v2 2/13] ACPI / hotplug / PCI: Move PCI rescan-remove locking to hotplug_event()

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

Commit 9217a984671e (ACPI / hotplug / PCI: Use global PCI rescan-remove
locking) modified ACPIPHP to protect its PCI device removal and addition
code paths from races against sysfs-driven rescan and remove operations
with the help of PCI rescan-remove locking.  However, it overlooked the
fact that hotplug_event_work() is not the only caller of hotplug_event()
which may also be called by dock_hotplug_event() and that code path
is missing the PCI rescan-remove locking.  This means that, although
the PCI rescan-remove lock is held as appropriate during the handling
of events originating from handle_hotplug_event(), the ACPIPHP's
operations resulting from dock events may still suffer the race
conditions that commit 9217a984671e was supposed to eliminate.

To address that problem, move the PCI rescan-remove locking from
hotplug_event_work() to hotplug_event() so that it is used regardless
of the way that function is invoked.

Revamps: 9217a984671e (ACPI / hotplug / PCI: Use global PCI rescan-remove locking)
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/pci/hotplug/acpiphp_glue.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-pm/drivers/pci/hotplug/acpiphp_glue.c
===================================================================
--- linux-pm.orig/drivers/pci/hotplug/acpiphp_glue.c
+++ linux-pm/drivers/pci/hotplug/acpiphp_glue.c
@@ -852,6 +852,7 @@ static void hotplug_event(acpi_handle ha

 	mutex_unlock(&acpiphp_context_lock);

+	pci_lock_rescan_remove();
 	acpi_get_name(handle, ACPI_FULL_PATHNAME, &buffer);

 	switch (type) {
@@ -905,6 +906,7 @@ static void hotplug_event(acpi_handle ha
 		break;
 	}

+	pci_unlock_rescan_remove();
 	if (bridge)
 		put_bridge(bridge);
 }
@@ -915,11 +917,9 @@ static void hotplug_event_work(void *dat
 	acpi_handle handle = context->handle;

 	acpi_scan_lock_acquire();
-	pci_lock_rescan_remove();

 	hotplug_event(handle, type, context);

-	pci_unlock_rescan_remove();
 	acpi_scan_lock_release();
 	acpi_evaluate_hotplug_ost(handle, type, ACPI_OST_SC_SUCCESS, NULL);
 	put_bridge(context->func.parent);

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