Commit 414428c5da1c ("PCI: hv: Lock PCI bus on device eject") added pci_lock_rescan_remove() and pci_unlock_rescan_remove() in create_root_hv_pci_bus() and in hv_eject_device_work() to address the race between create_root_hv_pci_bus() and hv_eject_device_work(), but it turns that grubing the pci_rescan_remove_lock mutex is not enough: refer to the earlier fix "PCI: hv: Add a per-bus mutex state_lock".
Now with hbus->state_lock and other fixes, the race is resolved, so remove pci_{lock,unlock}_rescan_remove() in create_root_hv_pci_bus(): this removes the serialization in hv_pci_probe() and hence allows async-probing (PROBE_PREFER_ASYNCHRONOUS) to work.
Add the async-probing flag to hv_pci_drv.
pci_{lock,unlock}_rescan_remove() in hv_eject_device_work() and in hv_pci_remove() are still kept: according to the comment before drivers/pci/probe.c: static DEFINE_MUTEX(pci_rescan_remove_lock), "PCI device removal routines should always be executed under this mutex".
Signed-off-by: Dexuan Cui decui@microsoft.com Cc: stable@vger.kernel.org ---
v2: No change to the patch body. Improved the commit message [Michael Kelley] Added Cc:stable
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 3ae2f99dea8c2..2ea2b1b8a4c9a 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)
From: Dexuan Cui decui@microsoft.com Sent: Monday, April 3, 2023 7:06 PM
Commit 414428c5da1c ("PCI: hv: Lock PCI bus on device eject") added pci_lock_rescan_remove() and pci_unlock_rescan_remove() in create_root_hv_pci_bus() and in hv_eject_device_work() to address the race between create_root_hv_pci_bus() and hv_eject_device_work(), but it turns that grubing the pci_rescan_remove_lock mutex is not enough: refer to the earlier fix "PCI: hv: Add a per-bus mutex state_lock".
Now with hbus->state_lock and other fixes, the race is resolved, so remove pci_{lock,unlock}_rescan_remove() in create_root_hv_pci_bus(): this removes the serialization in hv_pci_probe() and hence allows async-probing (PROBE_PREFER_ASYNCHRONOUS) to work.
Add the async-probing flag to hv_pci_drv.
pci_{lock,unlock}_rescan_remove() in hv_eject_device_work() and in hv_pci_remove() are still kept: according to the comment before drivers/pci/probe.c: static DEFINE_MUTEX(pci_rescan_remove_lock), "PCI device removal routines should always be executed under this mutex".
Signed-off-by: Dexuan Cui decui@microsoft.com Cc: stable@vger.kernel.org
v2: No change to the patch body. Improved the commit message [Michael Kelley] Added Cc:stable
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 3ae2f99dea8c2..2ea2b1b8a4c9a 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().*/
- 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
Reviewed-by: Michael Kelley mikelley@microsoft.com
From: Michael Kelley (LINUX) mikelley@microsoft.com Sent: Friday, April 7, 2023 9:12 AM
From: Dexuan Cui decui@microsoft.com Sent: Monday, April 3, 2023 7:06 PM
Commit 414428c5da1c ("PCI: hv: Lock PCI bus on device eject") added pci_lock_rescan_remove() and pci_unlock_rescan_remove() in create_root_hv_pci_bus() and in hv_eject_device_work() to address the race between create_root_hv_pci_bus() and hv_eject_device_work(), but it turns that grubing the pci_rescan_remove_lock mutex is not enough:
There's some kind of spelling error or typo above. Should "grubing" be "grabbing"? Or did you intend something else?
Michael
refer to the earlier fix "PCI: hv: Add a per-bus mutex state_lock".
Now with hbus->state_lock and other fixes, the race is resolved, so remove pci_{lock,unlock}_rescan_remove() in create_root_hv_pci_bus(): this removes the serialization in hv_pci_probe() and hence allows async-probing (PROBE_PREFER_ASYNCHRONOUS) to work.
Add the async-probing flag to hv_pci_drv.
pci_{lock,unlock}_rescan_remove() in hv_eject_device_work() and in hv_pci_remove() are still kept: according to the comment before drivers/pci/probe.c: static DEFINE_MUTEX(pci_rescan_remove_lock), "PCI device removal routines should always be executed under this mutex".
Signed-off-by: Dexuan Cui decui@microsoft.com Cc: stable@vger.kernel.org
From: Michael Kelley (LINUX) mikelley@microsoft.com Sent: Friday, April 7, 2023 9:15 AM ...
Commit 414428c5da1c ("PCI: hv: Lock PCI bus on device eject") added pci_lock_rescan_remove() and pci_unlock_rescan_remove() in create_root_hv_pci_bus() and in hv_eject_device_work() to address the race between create_root_hv_pci_bus() and hv_eject_device_work(), but it turns that grubing the pci_rescan_remove_lock mutex is not enough:
There's some kind of spelling error or typo above. Should "grubing" be "grabbing"? Or did you intend something else?
Michael
Sorry, it's a typo. The "grubing" should be "grabbing". I suppose the PCI maintainers can help fix this. Let me know if v3 is needed.
Subject: RE: [PATCH v2 6/6] PCI: hv: Use async probing to reduce boot time
From: Michael Kelley (LINUX) mikelley@microsoft.com Sent: Friday, April 7, 2023 9:15 AM ...
Commit 414428c5da1c ("PCI: hv: Lock PCI bus on device eject") added pci_lock_rescan_remove() and pci_unlock_rescan_remove() in create_root_hv_pci_bus() and in hv_eject_device_work() to address the race between create_root_hv_pci_bus() and hv_eject_device_work(), but it turns that grubing the
pci_rescan_remove_lock mutex is not enough:
There's some kind of spelling error or typo above. Should "grubing" be "grabbing"? Or did you intend something else?
Michael
Sorry, it's a typo. The "grubing" should be "grabbing". I suppose the PCI maintainers can help fix this. Let me know if v3 is needed.
Other than the typo,
Reviewed-by: Long Li longli@microsoft.com
linux-stable-mirror@lists.linaro.org
-
Dexuan Cui -
Long Li -
Michael Kelley (LINUX)