| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20130113232753.7225.31932.stgit@bhelgaas.mtv.corp.google.com>
Date: Sun, 13 Jan 2013 16:27:53 -0700
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: Yijing Wang <wangyijing@...wei.com>, linux-pci@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
Daniel J Blueman <daniel@...ra.org>,
Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
Tejun Heo <tj@...nel.org>, Yinghai Lu <yinghai@...nel.org>,
Jiang Liu <liuj97@...il.com>
Subject: [PATCH v7 4/4] 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@...wei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
CC: stable@...r.kernel.org
---
drivers/pci/hotplug/shpchp.h | 2 +-
drivers/pci/hotplug/shpchp_core.c | 26 ++++++++++++++------------
drivers/pci/hotplug/shpchp_ctrl.c | 6 +++---
3 files changed, 18 insertions(+), 16 deletions(-)
diff --git a/drivers/pci/hotplug/shpchp.h b/drivers/pci/hotplug/shpchp.h
index 1b69d95..b849f995 100644
--- a/drivers/pci/hotplug/shpchp.h
+++ b/drivers/pci/hotplug/shpchp.h
@@ -46,7 +46,6 @@
extern bool shpchp_poll_mode;
extern int shpchp_poll_time;
extern bool shpchp_debug;
-extern struct workqueue_struct *shpchp_wq;
#define dbg(format, arg...) \
do { \
@@ -90,6 +89,7 @@ struct slot {
struct list_head slot_list;
struct delayed_work work; /* work for button event */
struct mutex lock;
+ struct workqueue_struct *wq;
u8 hp_slot;
};
diff --git a/drivers/pci/hotplug/shpchp_core.c b/drivers/pci/hotplug/shpchp_core.c
index 3774e0d..3100c52 100644
--- a/drivers/pci/hotplug/shpchp_core.c
+++ b/drivers/pci/hotplug/shpchp_core.c
@@ -39,7 +39,6 @@
bool shpchp_debug;
bool shpchp_poll_mode;
int shpchp_poll_time;
-struct workqueue_struct *shpchp_wq;
#define DRIVER_VERSION "0.4"
#define DRIVER_AUTHOR "Dan Zink <dan.zink@...paq.com>, Greg Kroah-Hartman <greg@...ah.com>, Dely Sy <dely.l.sy@...el.com>"
@@ -128,6 +127,14 @@ static int init_slots(struct controller *ctrl)
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);
@@ -147,7 +154,7 @@ static int init_slots(struct controller *ctrl)
if (retval) {
ctrl_err(ctrl, "pci_hp_register failed with error %d\n",
retval);
- goto error_info;
+ goto error_slotwq;
}
get_power_status(hotplug_slot, &info->power_status);
@@ -159,6 +166,8 @@ static int init_slots(struct controller *ctrl)
}
return 0;
+error_slotwq:
+ destroy_workqueue(slot->wq);
error_info:
kfree(info);
error_hpslot:
@@ -179,7 +188,7 @@ void cleanup_slots(struct controller *ctrl)
slot = list_entry(tmp, struct slot, slot_list);
list_del(&slot->slot_list);
cancel_delayed_work(&slot->work);
- flush_workqueue(shpchp_wq);
+ destroy_workqueue(slot->wq);
pci_hp_deregister(slot->hotplug_slot);
}
}
@@ -362,18 +371,12 @@ static struct pci_driver shpc_driver = {
static int __init shpcd_init(void)
{
- int retval = 0;
-
- shpchp_wq = alloc_workqueue("shpchp", 0, 0);
- if (!shpchp_wq)
- return -ENOMEM;
+ int retval;
retval = pci_register_driver(&shpc_driver);
dbg("%s: pci_register_driver = %d\n", __func__, retval);
info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
- if (retval) {
- destroy_workqueue(shpchp_wq);
- }
+
return retval;
}
@@ -381,7 +384,6 @@ static void __exit shpcd_cleanup(void)
{
dbg("unload_shpchpd()\n");
pci_unregister_driver(&shpc_driver);
- destroy_workqueue(shpchp_wq);
info(DRIVER_DESC " version: " DRIVER_VERSION " unloaded\n");
}
diff --git a/drivers/pci/hotplug/shpchp_ctrl.c b/drivers/pci/hotplug/shpchp_ctrl.c
index fd2cae9..5849927 100644
--- a/drivers/pci/hotplug/shpchp_ctrl.c
+++ b/drivers/pci/hotplug/shpchp_ctrl.c
@@ -51,7 +51,7 @@ static int queue_interrupt_event(struct slot *p_slot, u32 event_type)
info->p_slot = p_slot;
INIT_WORK(&info->work, interrupt_event_handler);
- queue_work(shpchp_wq, &info->work);
+ queue_work(p_slot->wq, &info->work);
return 0;
}
@@ -453,7 +453,7 @@ void shpchp_queue_pushbutton_work(struct work_struct *work)
kfree(info);
goto out;
}
- queue_work(shpchp_wq, &info->work);
+ queue_work(p_slot->wq, &info->work);
out:
mutex_unlock(&p_slot->lock);
}
@@ -501,7 +501,7 @@ static void handle_button_press_event(struct slot *p_slot)
p_slot->hpc_ops->green_led_blink(p_slot);
p_slot->hpc_ops->set_attention_status(p_slot, 0);
- queue_delayed_work(shpchp_wq, &p_slot->work, 5*HZ);
+ queue_delayed_work(p_slot->wq, &p_slot->work, 5*HZ);
break;
case BLINKINGOFF_STATE:
case BLINKINGON_STATE:
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists