[PATCH v3 3/6] PCI: hv: serialize the present/eject work items

Dexuan Cui
2018-03-06T18:23:12Z

When we hot-remove the device, we first receive a PCI_EJECT message and
then receive a PCI_BUS_RELATIONS message with bus_rel->device_count == 0.

The first message is offloaded to hv_eject_device_work(), and the second
is offloaded to pci_devices_present_work(). Both the paths can be running
list_del(&hpdev->list_entry), causing general protection fault, because
system_wq can run them concurrently.

The patch eliminates the race condition.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Tested-by: Adrian Suhov <v-adsuho@microsoft.com>
Tested-by: Chris Valean <v-chvale@microsoft.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Jack Morgenstein <jackm@mellanox.com>
Cc: stable@vger.kernel.org
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
---
drivers/pci/host/pci-hyperv.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 04edb24c92ee..aaee41faf55f 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -461,6 +461,8 @@ struct hv_pcibus_device {
struct retarget_msi_interrupt retarget_msi_interrupt_params;

spinlock_t retarget_msi_interrupt_lock;
+
+ struct workqueue_struct *wq;
};

/*
@@ -1770,7 +1772,7 @@ static void hv_pci_devices_present(struct hv_pcibus_device *hbus,
spin_unlock_irqrestore(&hbus->device_list_lock, flags);

get_hvpcibus(hbus);
- schedule_work(&dr_wrk->wrk);
+ queue_work(hbus->wq, &dr_wrk->wrk);
}

/**
@@ -1845,7 +1847,7 @@ static void hv_pci_eject_device(struct hv_pci_dev *hpdev)
get_pcichild(hpdev, hv_pcidev_ref_pnp);
INIT_WORK(&hpdev->wrk, hv_eject_device_work);
get_hvpcibus(hpdev->hbus);
- schedule_work(&hpdev->wrk);
+ queue_work(hpdev->hbus->wq, &hpdev->wrk);
}

/**
@@ -2460,11 +2462,17 @@ static int hv_pci_probe(struct hv_device *hdev,
spin_lock_init(&hbus->retarget_msi_interrupt_lock);
sema_init(&hbus->enum_sem, 1);
init_completion(&hbus->remove_event);
+ hbus->wq = alloc_ordered_workqueue("hv_pci_%x", 0,
+ hbus->sysdata.domain);
+ if (!hbus->wq) {
+ ret = -ENOMEM;
+ goto free_bus;
+ }

ret = vmbus_open(hdev->channel, pci_ring_size, pci_ring_size, NULL, 0,
hv_pci_onchannelcallback, hbus);
if (ret)
- goto free_bus;
+ goto destroy_wq;

hv_set_drvdata(hdev, hbus);

@@ -2533,6 +2541,8 @@ static int hv_pci_probe(struct hv_device *hdev,
hv_free_config_window(hbus);
close:
vmbus_close(hdev->channel);
+destroy_wq:
+ destroy_workqueue(hbus->wq);
free_bus:
free_page((unsigned long)hbus);
return ret;
@@ -2612,6 +2622,7 @@ static int hv_pci_remove(struct hv_device *hdev)
irq_domain_free_fwnode(hbus->sysdata.fwnode);
put_hvpcibus(hbus);
wait_for_completion(&hbus->remove_event);
+ destroy_workqueue(hbus->wq);
free_page((unsigned long)hbus);
return 0;
}
--
2.7.4