linux-kernel - RE: [PATCH v2 6/6] PCI: hv: Use async probing to reduce boot time

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Date:   Fri, 7 Apr 2023 16:14:34 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        Dexuan Cui <decui@...rosoft.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Jake Oshins <jakeo@...rosoft.com>,
        "kuba@...nel.org" <kuba@...nel.org>, "kw@...ux.com" <kw@...ux.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "leon@...nel.org" <leon@...nel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "lpieralisi@...nel.org" <lpieralisi@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "robh@...nel.org" <robh@...nel.org>,
        "saeedm@...dia.com" <saeedm@...dia.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Long Li <longli@...rosoft.com>,
        "boqun.feng@...il.com" <boqun.feng@...il.com>,
        Saurabh Singh Sengar <ssengar@...rosoft.com>,
        "helgaas@...nel.org" <helgaas@...nel.org>
CC:     "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH v2 6/6] PCI: hv: Use async probing to reduce boot time

From: Michael Kelley (LINUX) <mikelley@...rosoft.com> Sent: Friday, April 7, 2023 9:12 AM
> 
> From: Dexuan Cui <decui@...rosoft.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@...rosoft.com>
> > Cc: stable@...r.kernel.org