PCI: pciehp: Use per-slot workqueues to avoid deadlock
When we have a hotplug-capable PCIe port with a second hotplug-capable
PCIe port below it, removing the device below the upstream port causes
a deadlock.
The deadlock happens because we use the pciehp_wq workqueue to run
pciehp_power_thread(), which uses pciehp_disable_slot() to remove devices
below the upstream port. When we remove the downstream PCIe port, we call
pciehp_remove(), the pciehp driver's .remove() method. That calls
flush_workqueue(pciehp_wq), which deadlocks because the
pciehp_power_thread() work item is still running.
This patch avoids the deadlock by creating a workqueue for every PCIe port
and removing the single shared workqueue.
Here's the call path that leads to the deadlock:
pciehp_queue_pushbutton_work
queue_work(pciehp_wq) # queue pciehp_power_thread
...
pciehp_power_thread
pciehp_disable_slot
remove_board
pciehp_unconfigure_device
pci_stop_and_remove_bus_device
...
pciehp_remove # pciehp driver .remove method
pciehp_release_ctrl
pcie_cleanup_slot
flush_workqueue(pciehp_wq)
This is fairly urgent because it can be caused by simply unplugging a
Thunderbolt adapter, as reported by Daniel below.
[bhelgaas: changelog]
Reference: http://lkml.kernel.org/r/CAMVG2ssiRgcTD1bej2tkUUfsWmpL5eNtPcNif9va2-Gzb2u8nQ@mail.gmail.com
Reported-and-tested-by: Daniel J Blueman <daniel@quora.org>
Reviewed-by: Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.orgdiff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
index 27f4429..38f0186 100644
--- a/drivers/pci/hotplug/pciehp_ctrl.c
+++ b/drivers/pci/hotplug/pciehp_ctrl.c
@@ -49,7 +49,7 @@
info->p_slot = p_slot;
INIT_WORK(&info->work, interrupt_event_handler);
- queue_work(pciehp_wq, &info->work);
+ queue_work(p_slot->wq, &info->work);
return 0;
}
@@ -344,7 +344,7 @@
kfree(info);
goto out;
}
- queue_work(pciehp_wq, &info->work);
+ queue_work(p_slot->wq, &info->work);
out:
mutex_unlock(&p_slot->lock);
}
@@ -377,7 +377,7 @@
if (ATTN_LED(ctrl))
pciehp_set_attention_status(p_slot, 0);
- queue_delayed_work(pciehp_wq, &p_slot->work, 5*HZ);
+ queue_delayed_work(p_slot->wq, &p_slot->work, 5*HZ);
break;
case BLINKINGOFF_STATE:
case BLINKINGON_STATE:
@@ -439,7 +439,7 @@
else
p_slot->state = POWERON_STATE;
- queue_work(pciehp_wq, &info->work);
+ queue_work(p_slot->wq, &info->work);
}
static void interrupt_event_handler(struct work_struct *work)