On Tuesday, November 26, 2013 06:26:54 PM Yinghai Lu wrote:
> On Tue, Nov 26, 2013 at 5:24 PM, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
> >
> > So assume pci_destroy_dev() is called twice in parallel for the same dev
> > by two different threads. Thread 1 does the atomic_inc_and_test() and
> > finds that it is OK to do the device_del() and put_device() which causes
> > the device object to be freed. Then thread 2 does the atomic_inc_and_test()
> > on the already freed device object and crashes the kernel.
> >
> thread2 should still hold one extra reference.
> that is in
> device_schedule_callback
> ==> sysfs_schedule_callback
> ==> kobject_get(kobj)
>
> pci_destroy_dev for thread2 is called at this point.
>
> and that reference will be released from
> sysfs_schedule_callback
> ==> kobject_put()...
Well, that would be the case if thread 2 was started by device_schedule_callback(),
but again, for example, it may be trim_stale_devices() started by acpiphp_check_bridge()
that doesn't hold extra references to the pci_dev. [Well, that piece of code
is racy anyway, because it walks bus->devices without locking. Which is my
fault too, because I overlooked that. Shame, shame.]
Perhaps we can do something like the (untested) patch below (in addition to the
$subject patch). Do you see any immediate problems with it?
Also I wonder if it is safe to do pci_stop_and_remove_device() in acpiphp_glue.c
without putting it under pci_remove_rescan_mutex?
Rafael
---
drivers/pci/hotplug/acpiphp_glue.c | 47 +++++++++++++++++++++++++------------
1 file changed, 33 insertions(+), 14 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
@@ -687,10 +687,11 @@ static unsigned int get_slot_status(stru
}
/**
- * trim_stale_devices - remove PCI devices that are not responding.
+ * find_stale_devices - Select PCI devices that are not responding for removal.
* @dev: PCI device to start walking the hierarchy from.
+ * @trim_list: List of devices to remove.
*/
-static void trim_stale_devices(struct pci_dev *dev)
+static void find_stale_devices(struct pci_dev *dev, struct list_head *trim_list)
{
acpi_handle handle = ACPI_HANDLE(&dev->dev);
struct pci_bus *bus = dev->subordinate;
@@ -710,21 +711,46 @@ static void trim_stale_devices(struct pc
alive = pci_bus_read_dev_vendor_id(dev->bus, dev->devfn, &v, 0);
}
if (!alive) {
- pci_stop_and_remove_bus_device(dev);
- if (handle)
- acpiphp_bus_trim(handle);
+ pci_dev_get(dev);
+ list_move(&dev->bus_list, trim_list);
} else if (bus) {
struct pci_dev *child, *tmp;
/* The device is a bridge. so check the bus below it. */
pm_runtime_get_sync(&dev->dev);
list_for_each_entry_safe(child, tmp, &bus->devices, bus_list)
- trim_stale_devices(child);
+ find_stale_devices(child, trim_list);
pm_runtime_put(&dev->dev);
}
}
+void acpiphp_trim_stale_devices(struct acpiphp_slot *slot)
+{
+ struct pci_bus *bus = slot->bus;
+ struct pci_dev *dev, *tmp;
+ LIST_HEAD(trim_list);
+
+ down_write(&pci_bus_sem);
+
+ list_for_each_entry_safe(dev, tmp, &bus->devices, bus_list)
+ if (PCI_SLOT(dev->devfn) == slot->device)
+ find_stale_devices(dev, &trim_list);
+
+ up_write(&pci_bus_sem);
+
+ while (!list_empty(&trim_list)) {
+ acpi_handle handle;
+
+ dev = list_first_entry(&trim_list, struct pci_dev, bus_list);
+ handle = ACPI_HANDLE(&dev->dev);
+ pci_stop_and_remove_bus_device(dev);
+ pci_dev_put(dev);
+ if (handle)
+ acpiphp_bus_trim(handle);
+ }
+}
+
/**
* acpiphp_check_bridge - re-enumerate devices
* @bridge: where to begin re-enumeration
@@ -737,18 +763,11 @@ static void acpiphp_check_bridge(struct
struct acpiphp_slot *slot;
list_for_each_entry(slot, &bridge->slots, node) {
- struct pci_bus *bus = slot->bus;
- struct pci_dev *dev, *tmp;
-
mutex_lock(&slot->crit_sect);
/* wake up all functions */
if (get_slot_status(slot) == ACPI_STA_ALL) {
/* remove stale devices if any */
- list_for_each_entry_safe(dev, tmp, &bus->devices,
- bus_list)
- if (PCI_SLOT(dev->devfn) == slot->device)
- trim_stale_devices(dev);
-
+ acpiphp_trim_stale_devices(slot);
/* configure all functions */
enable_slot(slot);
} else {
--
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