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linux/drivers/pci/hotplug/shpchp_core.c
Bjorn Helgaas f652e7d291 PCI: shpchp: Use per-slot workqueues to avoid deadlock 
When we have an SHPC-capable bridge with a second SHPC-capable bridge
below it, pushing the upstream bridge's attention button causes a
deadlock.

The deadlock happens because we use the shpchp_wq workqueue to run
shpchp_pushbutton_thread(), which uses shpchp_disable_slot() to remove
devices below the upstream bridge.  When we remove the downstream bridge,
we call shpc_remove(), the shpchp driver's .remove() method.  That calls
flush_workqueue(shpchp_wq), which deadlocks because the
shpchp_pushbutton_thread() work item is still running.

This patch avoids the deadlock by creating a workqueue for every slot
and removing the single shared workqueue.

Here's the call path that leads to the deadlock:

  shpchp_queue_pushbutton_work
    queue_work(shpchp_wq)		# shpchp_pushbutton_thread
    ...

  shpchp_pushbutton_thread
    shpchp_disable_slot
      remove_board
        shpchp_unconfigure_device
          pci_stop_and_remove_bus_device
            ...
              shpc_remove		# shpchp driver .remove method
                hpc_release_ctlr
                  cleanup_slots
                    flush_workqueue(shpchp_wq)

This change is based on code inspection, since we don't have hardware
with this topology.

Based-on-patch-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org
2013-01-14 10:23:22 -07:00

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/*
* Standard Hot Plug Controller Driver
*
* Copyright (C) 1995,2001 Compaq Computer Corporation
* Copyright (C) 2001 Greg Kroah-Hartman (greg@kroah.com)
* Copyright (C) 2001 IBM Corp.
* Copyright (C) 2003-2004 Intel Corporation
*
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
* NON INFRINGEMENT. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* Send feedback to <greg@kroah.com>, <kristen.c.accardi@intel.com>
*
*/
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/pci.h>
#include "shpchp.h"
/* Global variables */
bool shpchp_debug;
bool shpchp_poll_mode;
int shpchp_poll_time;
#define DRIVER_VERSION "0.4"
#define DRIVER_AUTHOR "Dan Zink <dan.zink@compaq.com>, Greg Kroah-Hartman <greg@kroah.com>, Dely Sy <dely.l.sy@intel.com>"
#define DRIVER_DESC "Standard Hot Plug PCI Controller Driver"
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");
module_param(shpchp_debug, bool, 0644);
module_param(shpchp_poll_mode, bool, 0644);
module_param(shpchp_poll_time, int, 0644);
MODULE_PARM_DESC(shpchp_debug, "Debugging mode enabled or not");
MODULE_PARM_DESC(shpchp_poll_mode, "Using polling mechanism for hot-plug events or not");
MODULE_PARM_DESC(shpchp_poll_time, "Polling mechanism frequency, in seconds");
#define SHPC_MODULE_NAME "shpchp"
static int set_attention_status (struct hotplug_slot *slot, u8 value);
static int enable_slot (struct hotplug_slot *slot);
static int disable_slot (struct hotplug_slot *slot);
static int get_power_status (struct hotplug_slot *slot, u8 *value);
static int get_attention_status (struct hotplug_slot *slot, u8 *value);
static int get_latch_status (struct hotplug_slot *slot, u8 *value);
static int get_adapter_status (struct hotplug_slot *slot, u8 *value);
static struct hotplug_slot_ops shpchp_hotplug_slot_ops = {
.set_attention_status = set_attention_status,
.enable_slot = enable_slot,
.disable_slot = disable_slot,
.get_power_status = get_power_status,
.get_attention_status = get_attention_status,
.get_latch_status = get_latch_status,
.get_adapter_status = get_adapter_status,
};
/**
* release_slot - free up the memory used by a slot
* @hotplug_slot: slot to free
*/
static void release_slot(struct hotplug_slot *hotplug_slot)
{
struct slot *slot = hotplug_slot->private;
ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
__func__, slot_name(slot));
kfree(slot->hotplug_slot->info);
kfree(slot->hotplug_slot);
kfree(slot);
}
static int init_slots(struct controller *ctrl)
{
struct slot *slot;
struct hotplug_slot *hotplug_slot;
struct hotplug_slot_info *info;
char name[SLOT_NAME_SIZE];
int retval;
int i;
for (i = 0; i < ctrl->num_slots; i++) {
slot = kzalloc(sizeof(*slot), GFP_KERNEL);
if (!slot) {
retval = -ENOMEM;
goto error;
}
hotplug_slot = kzalloc(sizeof(*hotplug_slot), GFP_KERNEL);
if (!hotplug_slot) {
retval = -ENOMEM;
goto error_slot;
}
slot->hotplug_slot = hotplug_slot;
info = kzalloc(sizeof(*info), GFP_KERNEL);
if (!info) {
retval = -ENOMEM;
goto error_hpslot;
}
hotplug_slot->info = info;
slot->hp_slot = i;
slot->ctrl = ctrl;
slot->bus = ctrl->pci_dev->subordinate->number;
slot->device = ctrl->slot_device_offset + i;
slot->hpc_ops = ctrl->hpc_ops;
slot->number = ctrl->first_slot + (ctrl->slot_num_inc * i);
snprintf(name, sizeof(name), "shpchp-%d", slot->number);
slot->wq = alloc_workqueue(name, 0, 0);
if (!slot->wq) {
retval = -ENOMEM;
goto error_info;
}
mutex_init(&slot->lock);
INIT_DELAYED_WORK(&slot->work, shpchp_queue_pushbutton_work);
/* register this slot with the hotplug pci core */
hotplug_slot->private = slot;
hotplug_slot->release = &release_slot;
snprintf(name, SLOT_NAME_SIZE, "%d", slot->number);
hotplug_slot->ops = &shpchp_hotplug_slot_ops;
ctrl_dbg(ctrl, "Registering domain:bus:dev=%04x:%02x:%02x "
"hp_slot=%x sun=%x slot_device_offset=%x\n",
pci_domain_nr(ctrl->pci_dev->subordinate),
slot->bus, slot->device, slot->hp_slot, slot->number,
ctrl->slot_device_offset);
retval = pci_hp_register(slot->hotplug_slot,
ctrl->pci_dev->subordinate, slot->device, name);
if (retval) {
ctrl_err(ctrl, "pci_hp_register failed with error %d\n",
retval);
goto error_slotwq;
}
get_power_status(hotplug_slot, &info->power_status);
get_attention_status(hotplug_slot, &info->attention_status);
get_latch_status(hotplug_slot, &info->latch_status);
get_adapter_status(hotplug_slot, &info->adapter_status);
list_add(&slot->slot_list, &ctrl->slot_list);
}
return 0;
error_slotwq:
destroy_workqueue(slot->wq);
error_info:
kfree(info);
error_hpslot:
kfree(hotplug_slot);
error_slot:
kfree(slot);
error:
return retval;
}
void cleanup_slots(struct controller *ctrl)
{
struct list_head *tmp;
struct list_head *next;
struct slot *slot;
list_for_each_safe(tmp, next, &ctrl->slot_list) {
slot = list_entry(tmp, struct slot, slot_list);
list_del(&slot->slot_list);
cancel_delayed_work(&slot->work);
destroy_workqueue(slot->wq);
pci_hp_deregister(slot->hotplug_slot);
}
}
/*
* set_attention_status - Turns the Amber LED for a slot on, off or blink
*/
static int set_attention_status (struct hotplug_slot *hotplug_slot, u8 status)
{
struct slot *slot = get_slot(hotplug_slot);
ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
__func__, slot_name(slot));
hotplug_slot->info->attention_status = status;
slot->hpc_ops->set_attention_status(slot, status);
return 0;
}
static int enable_slot (struct hotplug_slot *hotplug_slot)
{
struct slot *slot = get_slot(hotplug_slot);
ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
__func__, slot_name(slot));
return shpchp_sysfs_enable_slot(slot);
}
static int disable_slot (struct hotplug_slot *hotplug_slot)
{
struct slot *slot = get_slot(hotplug_slot);
ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
__func__, slot_name(slot));
return shpchp_sysfs_disable_slot(slot);
}
static int get_power_status (struct hotplug_slot *hotplug_slot, u8 *value)
{
struct slot *slot = get_slot(hotplug_slot);
int retval;
ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
__func__, slot_name(slot));
retval = slot->hpc_ops->get_power_status(slot, value);
if (retval < 0)
*value = hotplug_slot->info->power_status;
return 0;
}
static int get_attention_status (struct hotplug_slot *hotplug_slot, u8 *value)
{
struct slot *slot = get_slot(hotplug_slot);
int retval;
ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
__func__, slot_name(slot));
retval = slot->hpc_ops->get_attention_status(slot, value);
if (retval < 0)
*value = hotplug_slot->info->attention_status;
return 0;
}
static int get_latch_status (struct hotplug_slot *hotplug_slot, u8 *value)
{
struct slot *slot = get_slot(hotplug_slot);
int retval;
ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
__func__, slot_name(slot));
retval = slot->hpc_ops->get_latch_status(slot, value);
if (retval < 0)
*value = hotplug_slot->info->latch_status;
return 0;
}
static int get_adapter_status (struct hotplug_slot *hotplug_slot, u8 *value)
{
struct slot *slot = get_slot(hotplug_slot);
int retval;
ctrl_dbg(slot->ctrl, "%s: physical_slot = %s\n",
__func__, slot_name(slot));
retval = slot->hpc_ops->get_adapter_status(slot, value);
if (retval < 0)
*value = hotplug_slot->info->adapter_status;
return 0;
}
static int is_shpc_capable(struct pci_dev *dev)
{
if (dev->vendor == PCI_VENDOR_ID_AMD &&
dev->device == PCI_DEVICE_ID_AMD_GOLAM_7450)
return 1;
if (!pci_find_capability(dev, PCI_CAP_ID_SHPC))
return 0;
if (get_hp_hw_control_from_firmware(dev))
return 0;
return 1;
}
static int shpc_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
{
int rc;
struct controller *ctrl;
if (!is_shpc_capable(pdev))
return -ENODEV;
ctrl = kzalloc(sizeof(*ctrl), GFP_KERNEL);
if (!ctrl) {
dev_err(&pdev->dev, "%s: Out of memory\n", __func__);
goto err_out_none;
}
INIT_LIST_HEAD(&ctrl->slot_list);
rc = shpc_init(ctrl, pdev);
if (rc) {
ctrl_dbg(ctrl, "Controller initialization failed\n");
goto err_out_free_ctrl;
}
pci_set_drvdata(pdev, ctrl);
/* Setup the slot information structures */
rc = init_slots(ctrl);
if (rc) {
ctrl_err(ctrl, "Slot initialization failed\n");
goto err_out_release_ctlr;
}
rc = shpchp_create_ctrl_files(ctrl);
if (rc)
goto err_cleanup_slots;
return 0;
err_cleanup_slots:
cleanup_slots(ctrl);
err_out_release_ctlr:
ctrl->hpc_ops->release_ctlr(ctrl);
err_out_free_ctrl:
kfree(ctrl);
err_out_none:
return -ENODEV;
}
static void shpc_remove(struct pci_dev *dev)
{
struct controller *ctrl = pci_get_drvdata(dev);
shpchp_remove_ctrl_files(ctrl);
ctrl->hpc_ops->release_ctlr(ctrl);
kfree(ctrl);
}
static struct pci_device_id shpcd_pci_tbl[] = {
{PCI_DEVICE_CLASS(((PCI_CLASS_BRIDGE_PCI << 8) | 0x00), ~0)},
{ /* end: all zeroes */ }
};
MODULE_DEVICE_TABLE(pci, shpcd_pci_tbl);
static struct pci_driver shpc_driver = {
.name = SHPC_MODULE_NAME,
.id_table = shpcd_pci_tbl,
.probe = shpc_probe,
.remove = shpc_remove,
};
static int __init shpcd_init(void)
{
int retval;
retval = pci_register_driver(&shpc_driver);
dbg("%s: pci_register_driver = %d\n", __func__, retval);
info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
return retval;
}
static void __exit shpcd_cleanup(void)
{
dbg("unload_shpchpd()\n");
pci_unregister_driver(&shpc_driver);
info(DRIVER_DESC " version: " DRIVER_VERSION " unloaded\n");
}
module_init(shpcd_init);
module_exit(shpcd_cleanup);
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