From: longli@linuxonhyperv.com
To: "K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Wei Liu <wei.liu@kernel.org>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Rob Herring <robh@kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
linux-hyperv@vger.kernel.org, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: Long Li <longli@microsoft.com>
Subject: [Patch v3 1/2] PCI: hv: Fix a race condition when removing the device
Date: Wed, 12 May 2021 01:06:40 -0700 [thread overview]
Message-ID: <1620806800-30983-1-git-send-email-longli@linuxonhyperv.com> (raw)
From: Long Li <longli@microsoft.com>
On removing the device, any work item (hv_pci_devices_present() or
hv_pci_eject_device()) scheduled on workqueue hbus->wq may still be running
and race with hv_pci_remove().
This can happen because the host may send PCI_EJECT or PCI_BUS_RELATIONS(2)
and decide to rescind the channel immediately after that.
Fix this by flushing/destroying the workqueue of hbus before doing hbus remove.
Signed-off-by: Long Li <longli@microsoft.com>
---
Change in v2: Remove unused bus state hv_pcibus_removed
Change in v3: Change hv_pci_bus_exit() to not use workqueue to remove PCI devices
drivers/pci/controller/pci-hyperv.c | 30 ++++++++++++++++++++++-------
1 file changed, 23 insertions(+), 7 deletions(-)
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 27a17a1e4a7c..c6122a1b0c46 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -444,7 +444,6 @@ enum hv_pcibus_state {
hv_pcibus_probed,
hv_pcibus_installed,
hv_pcibus_removing,
- hv_pcibus_removed,
hv_pcibus_maximum
};
@@ -3247,8 +3246,9 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs)
struct pci_packet teardown_packet;
u8 buffer[sizeof(struct pci_message)];
} pkt;
- struct hv_dr_state *dr;
struct hv_pci_compl comp_pkt;
+ struct hv_pci_dev *hpdev, *tmp;
+ unsigned long flags;
int ret;
/*
@@ -3260,9 +3260,16 @@ static int hv_pci_bus_exit(struct hv_device *hdev, bool keep_devs)
if (!keep_devs) {
/* Delete any children which might still exist. */
- dr = kzalloc(sizeof(*dr), GFP_KERNEL);
- if (dr && hv_pci_start_relations_work(hbus, dr))
- kfree(dr);
+ spin_lock_irqsave(&hbus->device_list_lock, flags);
+ list_for_each_entry_safe(hpdev, tmp, &hbus->children, list_entry) {
+ list_del(&hpdev->list_entry);
+ if (hpdev->pci_slot)
+ pci_destroy_slot(hpdev->pci_slot);
+ /* For the two refs got in new_pcichild_device() */
+ put_pcichild(hpdev);
+ put_pcichild(hpdev);
+ }
+ spin_unlock_irqrestore(&hbus->device_list_lock, flags);
}
ret = hv_send_resources_released(hdev);
@@ -3305,13 +3312,23 @@ static int hv_pci_remove(struct hv_device *hdev)
hbus = hv_get_drvdata(hdev);
if (hbus->state == hv_pcibus_installed) {
+ tasklet_disable(&hdev->channel->callback_event);
+ hbus->state = hv_pcibus_removing;
+ tasklet_enable(&hdev->channel->callback_event);
+ destroy_workqueue(hbus->wq);
+ hbus->wq = NULL;
+ /*
+ * At this point, no work is running or can be scheduled
+ * on hbus-wq. We can't race with hv_pci_devices_present()
+ * or hv_pci_eject_device(), it's safe to proceed.
+ */
+
/* Remove the bus from PCI's point of view. */
pci_lock_rescan_remove();
pci_stop_root_bus(hbus->pci_bus);
hv_pci_remove_slots(hbus);
pci_remove_root_bus(hbus->pci_bus);
pci_unlock_rescan_remove();
- hbus->state = hv_pcibus_removed;
}
ret = hv_pci_bus_exit(hdev, false);
@@ -3326,7 +3343,6 @@ 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);
hv_put_dom_num(hbus->sysdata.domain);
--
2.27.0
next reply other threads:[~2021-05-12 8:06 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 8:06 longli [this message]
2021-05-26 18:55 ` [Patch v3 1/2] PCI: hv: Fix a race condition when removing the device Michael Kelley
2021-06-03 17:36 ` Lorenzo Pieralisi
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