[patch 26/45] PCI: Fix fakephp deadlock

Greg KH
2008-02-07T21:03:31Z

[-- Attachment #1: pci-fix-fakephp-deadlock.patch --]
[-- Type: text/plain, Size: 4073 bytes --]

2.6.24-stable review patch. If anyone has any objections, please let us know.

------------------
From: Ian Abbott <abbotti@mev.co.uk>

This patch works around a problem in the fakephp driver when a process
writing "0" to a "power" sysfs file to fake removal of a PCI device ends
up deadlocking itself in the sysfs code.

The patch was recently accepted into Linus' tree after the 2.6.24 release:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=5c796ae7a7ebe56967ed9b9963d7c16d733635ff

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/pci/hotplug/fakephp.c | 39 +++++++++++++++++++++++++++++++++++----
1 file changed, 35 insertions(+), 4 deletions(-)

--- a/drivers/pci/hotplug/fakephp.c
+++ b/drivers/pci/hotplug/fakephp.c
@@ -39,6 +39,7 @@
#include <linux/init.h>
#include <linux/string.h>
#include <linux/slab.h>
+#include <linux/workqueue.h>
#include "../pci.h"

#if !defined(MODULE)
@@ -63,10 +64,16 @@ struct dummy_slot {
struct list_head node;
struct hotplug_slot *slot;
struct pci_dev *dev;
+ struct work_struct remove_work;
+ unsigned long removed;
};

static int debug;
static LIST_HEAD(slot_list);
+static struct workqueue_struct *dummyphp_wq;
+
+static void pci_rescan_worker(struct work_struct *work);
+static DECLARE_WORK(pci_rescan_work, pci_rescan_worker);

static int enable_slot (struct hotplug_slot *slot);
static int disable_slot (struct hotplug_slot *slot);
@@ -109,7 +116,7 @@ static int add_slot(struct pci_dev *dev)
slot->name = &dev->dev.bus_id[0];
dbg("slot->name = %s\n", slot->name);

- dslot = kmalloc(sizeof(struct dummy_slot), GFP_KERNEL);
+ dslot = kzalloc(sizeof(struct dummy_slot), GFP_KERNEL);
if (!dslot)
goto error_info;

@@ -164,6 +171,14 @@ static void remove_slot(struct dummy_slo
err("Problem unregistering a slot %s\n", dslot->slot->name);
}

+/* called from the single-threaded workqueue handler to remove a slot */
+static void remove_slot_worker(struct work_struct *work)
+{
+ struct dummy_slot *dslot =
+ container_of(work, struct dummy_slot, remove_work);
+ remove_slot(dslot);
+}
+
/**
* pci_rescan_slot - Rescan slot
* @temp: Device template. Should be set: bus and devfn.
@@ -267,11 +282,17 @@ static inline void pci_rescan(void) {
pci_rescan_buses(&pci_root_buses);
}

+/* called from the single-threaded workqueue handler to rescan all pci buses */
+static void pci_rescan_worker(struct work_struct *work)
+{
+ pci_rescan();
+}

static int enable_slot(struct hotplug_slot *hotplug_slot)
{
/* mis-use enable_slot for rescanning of the pci bus */
- pci_rescan();
+ cancel_work_sync(&pci_rescan_work);
+ queue_work(dummyphp_wq, &pci_rescan_work);
return -ENODEV;
}

@@ -306,6 +327,10 @@ static int disable_slot(struct hotplug_s
err("Can't remove PCI devices with other PCI devices behind it yet.\n");
return -ENODEV;
}
+ if (test_and_set_bit(0, &dslot->removed)) {
+ dbg("Slot already scheduled for removal\n");
+ return -ENODEV;
+ }
/* search for subfunctions and disable them first */
if (!(dslot->dev->devfn & 7)) {
for (func = 1; func < 8; func++) {
@@ -328,8 +353,9 @@ static int disable_slot(struct hotplug_s
/* remove the device from the pci core */
pci_remove_bus_device(dslot->dev);

- /* blow away this sysfs entry and other parts. */
- remove_slot(dslot);
+ /* queue work item to blow away this sysfs entry and other parts. */
+ INIT_WORK(&dslot->remove_work, remove_slot_worker);
+ queue_work(dummyphp_wq, &dslot->remove_work);

return 0;
}
@@ -340,6 +366,7 @@ static void cleanup_slots (void)
struct list_head *next;
struct dummy_slot *dslot;

+ destroy_workqueue(dummyphp_wq);
list_for_each_safe (tmp, next, &slot_list) {
dslot = list_entry (tmp, struct dummy_slot, node);
remove_slot(dslot);
@@ -351,6 +378,10 @@ static int __init dummyphp_init(void)
{
info(DRIVER_DESC "\n");

+ dummyphp_wq = create_singlethread_workqueue(MY_NAME);
+ if (!dummyphp_wq)
+ return -ENOMEM;
+
return pci_scan_buses();
}

--