From: Yijing Wang Date: Fri, 17 Jul 2015 09:16:31 +0000 (+0800) Subject: PCI: Protect pci_bus->slots with pci_slot_mutex, not pci_bus_sem X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=67546762978f523749eac157903e0b01c18e083a;p=linux-beck.git 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 Tested-by: Guenter Roeck Signed-off-by: Yijing Wang Signed-off-by: Bjorn Helgaas --- 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); diff --git a/include/linux/pci.h b/include/linux/pci.h index 8a0321a8fb59..aaee493174e2 100644 --- a/include/linux/pci.h +++ b/include/linux/pci.h @@ -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 */