Rajat Jain reported a deadlock when a hierarchical hot plug thread and aer recovery thread both run. https://lkml.org/lkml/2015/3/11/861 thread 1: pciehp_enable_slot() pciehp_configure_device() pci_bus_add_devices() device_attach(dev) device_lock(dev) //acquire device mutex successfully ... pciehp_probe(dev) __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() pci_walk_bus() down_read(&pci_bus_sem) //acquire pci_bus_sem successfully report_error_detected(dev) device_lock(dev) // deadlock here Now we use pci_bus_sem to protect pci_slot creation and destroy, it's unnecessary. We could introduce a new local mutex instead of pci_bus_sem to avoid the deadlock. Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx> --- drivers/pci/slot.c | 11 ++++++----- 1 files changed, 6 insertions(+), 5 deletions(-) diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c index 396c200..feb08de 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) @@ -195,7 +196,7 @@ 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 so don't worry */ list_for_each_entry(slot, &parent->slots, list) if (slot->number == slot_nr) { @@ -253,7 +254,7 @@ 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; @@ -310,7 +311,7 @@ placeholder: out: kfree(slot_name); - up_write(&pci_bus_sem); + mutex_unlock(&pci_slot_mutex); return slot; err: kfree(slot); @@ -332,9 +333,9 @@ 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); -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
