netdev - [PATCH 6/6] PCI: hv: Use async probing to reduce boot time

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Date:   Mon, 27 Mar 2023 21:51:22 -0700
From:   Dexuan Cui <decui@...rosoft.com>
To:     bhelgaas@...gle.com, davem@...emloft.net, decui@...rosoft.com,
        edumazet@...gle.com, haiyangz@...rosoft.com, jakeo@...rosoft.com,
        kuba@...nel.org, kw@...ux.com, kys@...rosoft.com, leon@...nel.org,
        linux-pci@...r.kernel.org, lpieralisi@...nel.org,
        mikelley@...rosoft.com, pabeni@...hat.com, robh@...nel.org,
        saeedm@...dia.com, wei.liu@...nel.org, longli@...rosoft.com,
        boqun.feng@...il.com
Cc:     linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rdma@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH 6/6] PCI: hv: Use async probing to reduce boot time

Commit 414428c5da1c ("PCI: hv: Lock PCI bus on device eject") added the
pci_lock_rescan_remove() and pci_unlock_rescan_remove() to address the
race between create_root_hv_pci_bus() and hv_eject_device_work(), but it
doesn't really work well.

Now with hbus->state_lock and other fixes, the race is resolved, so
remove pci_{lock,unlock}_rescan_remove().

Also enable async probing to reduce boot time.

Signed-off-by: Dexuan Cui <decui@...rosoft.com>
---
 drivers/pci/controller/pci-hyperv.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 2c0b86b20408..08ab389e27cc 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -2312,12 +2312,16 @@ static int create_root_hv_pci_bus(struct hv_pcibus_device *hbus)
 	if (error)
 		return error;
 
-	pci_lock_rescan_remove();
+	/*
+	 * pci_lock_rescan_remove() and pci_unlock_rescan_remove() are
+	 * unnecessary here, because we hold the hbus->state_lock, meaning
+	 * hv_eject_device_work() and pci_devices_present_work() can't race
+	 * with create_root_hv_pci_bus().
+	 */
 	hv_pci_assign_numa_node(hbus);
 	pci_bus_assign_resources(bridge->bus);
 	hv_pci_assign_slots(hbus);
 	pci_bus_add_devices(bridge->bus);
-	pci_unlock_rescan_remove();
 	hbus->state = hv_pcibus_installed;
 	return 0;
 }
@@ -4003,6 +4007,9 @@ static struct hv_driver hv_pci_drv = {
 	.remove		= hv_pci_remove,
 	.suspend	= hv_pci_suspend,
 	.resume		= hv_pci_resume,
+	.driver = {
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
 };
 
 static void __exit exit_hv_pci_drv(void)
-- 
2.25.1