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PCI: Protect pci_bus->slots with pci_slot_mutex, not pci_bus_sem

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Rajat Jain reported a deadlock when PCIe hot-add and AER recovery happen at
the same time:

thread 1:

  pciehp_enable_slot
    pciehp_configure_device
      pci_bus_add_devices
        pci_bus_add_device
          device_attach
            device_lock(dev)                       # acquire device lock
            ...
            pciehp_probe
              init_slot
                pci_hp_register
                  pci_create_slot
                    down_write(pci_bus_sem)        # deadlock here

thread 2:

  aer_isr_one_error
    aer_process_err_device
      do_recovery
        broadcast_error_message(..., report_error_detected)
          pci_walk_bus(..., cb=report_error_detected, ...)
            down_read(&pci_bus_sem)                # acquire pci_bus_sem
            report_error_detected(dev)             # cb()
              device_lock(dev)                     # deadlock here

Previously, the bus->devices and bus->slots list were protected by
pci_bus_sem.  In pci_create_slot(), we held it for writing so we could
add to the bus->slots list.

Add a new local pci_slot_mutex to protect bus->slots.  Hold pci_bus_sem for
reading while searching the bus->devices list.

[bhelgaas: changelog]
Link: http://lkml.kernel.org/r/CAA93t1qpPqbih+UB0McA_d_+2rVaNkXsinAUxYzK9+JXSS+L-g@mail.gmail.com
Reported-by: Rajat Jain <rajatja@google.com>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
This commit is contained in:
Yijing Wang 2015-07-17 17:16:31 +08:00 committed by Bjorn Helgaas
parent ac10836b68
commit 6754676297
2 changed files with 13 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
drivers/pci/slot.c
View File

@ -14,6 +14,7 @@
struct kset *pci_slots_kset;
EXPORT_SYMBOL_GPL(pci_slots_kset);
static DEFINE_MUTEX(pci_slot_mutex);
static ssize_t pci_slot_attr_show(struct kobject *kobj,
struct attribute *attr, char *buf)
@ -106,9 +107,11 @@ static void pci_slot_release(struct kobject *kobj)
dev_dbg(&slot->bus->dev, "dev %02x, released physical slot %s\n",
slot->number, pci_slot_name(slot));
down_read(&pci_bus_sem);
list_for_each_entry(dev, &slot->bus->devices, bus_list)
if (PCI_SLOT(dev->devfn) == slot->number)
dev->slot = NULL;
up_read(&pci_bus_sem);
list_del(&slot->list);
@ -194,9 +197,8 @@ static int rename_slot(struct pci_slot *slot, const char *name)
static struct pci_slot *get_slot(struct pci_bus *parent, int slot_nr)
{
struct pci_slot *slot;
/*
* We already hold pci_bus_sem so don't worry
*/
/* We already hold pci_slot_mutex */
list_for_each_entry(slot, &parent->slots, list)
if (slot->number == slot_nr) {
kobject_get(&slot->kobj);
@ -253,7 +255,7 @@ struct pci_slot *pci_create_slot(struct pci_bus *parent, int slot_nr,
int err = 0;
char *slot_name = NULL;
down_write(&pci_bus_sem);
mutex_lock(&pci_slot_mutex);
if (slot_nr == -1)
goto placeholder;
@ -301,16 +303,18 @@ placeholder:
INIT_LIST_HEAD(&slot->list);
list_add(&slot->list, &parent->slots);
down_read(&pci_bus_sem);
list_for_each_entry(dev, &parent->devices, bus_list)
if (PCI_SLOT(dev->devfn) == slot_nr)
dev->slot = slot;
up_read(&pci_bus_sem);
dev_dbg(&parent->dev, "dev %02x, created physical slot %s\n",
slot_nr, pci_slot_name(slot));
out:
kfree(slot_name);
up_write(&pci_bus_sem);
mutex_unlock(&pci_slot_mutex);
return slot;
err:
kfree(slot);
@ -332,9 +336,9 @@ void pci_destroy_slot(struct pci_slot *slot)
dev_dbg(&slot->bus->dev, "dev %02x, dec refcount to %d\n",
slot->number, atomic_read(&slot->kobj.kref.refcount) - 1);
down_write(&pci_bus_sem);
mutex_lock(&pci_slot_mutex);
kobject_put(&slot->kobj);
up_write(&pci_bus_sem);
mutex_unlock(&pci_slot_mutex);
}
EXPORT_SYMBOL_GPL(pci_destroy_slot);

3
include/linux/pci.h
View File

@ -446,7 +446,8 @@ struct pci_bus {
struct list_head children; /* list of child buses */
struct list_head devices; /* list of devices on this bus */
struct pci_dev *self; /* bridge device as seen by parent */
struct list_head slots; /* list of slots on this bus */
struct list_head slots; /* list of slots on this bus;
protected by pci_slot_mutex */
struct resource *resource[PCI_BRIDGE_RESOURCE_NUM];
struct list_head resources; /* address space routed to this bus */
struct resource busn_res; /* bus numbers routed to this bus */