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authorYijing Wang <wangyijing@huawei.com>2015-07-17 17:16:31 +0800
committerBjorn Helgaas <bhelgaas@google.com>2015-07-30 15:49:10 -0500
commit67546762978f523749eac157903e0b01c18e083a (patch)
tree646a5a8749dae0c3192d9db23dc4eb1f63f90f75 /drivers/pci/slot.c
parentac10836b681289f7e430e52b106a209bbdcaa75e (diff)
PCI: Protect pci_bus->slots with pci_slot_mutex, not pci_bus_sem
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>
Diffstat (limited to 'drivers/pci/slot.c')
-rw-r--r--drivers/pci/slot.c18
1 files changed, 11 insertions, 7 deletions
diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
index 396c200b9ddb..4bd3fce93fa4 100644
--- a/drivers/pci/slot.c
+++ b/drivers/pci/slot.c
@@ -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);