linux-kernel - RE: [PATCH v3 4/6] Revert "PCI: hv: Fix a timing issue which causes kdump to fail occasionally"

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Message-ID: <SA1PR21MB13359A78EF24E0848BE58266BF5BA@SA1PR21MB1335.namprd21.prod.outlook.com>
Date:   Thu, 15 Jun 2023 04:41:58 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Lorenzo Pieralisi <lpieralisi@...nel.org>
CC:     "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>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        "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>,
        "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>,
        Jose Teuttli Carranco <josete@...rosoft.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH v3 4/6] Revert "PCI: hv: Fix a timing issue which causes
 kdump to fail occasionally"

> From: Lorenzo Pieralisi <lpieralisi@...nel.org>
> Sent: Thursday, May 25, 2023 1:23 AM
> ...
> On Wed, Apr 19, 2023 at 07:40:35PM -0700, Dexuan Cui wrote:
> > This reverts commit d6af2ed29c7c1c311b96dac989dcb991e90ee195.
> >
> > The statement "the hv_pci_bus_exit() call releases structures of all its
> > child devices" in commit d6af2ed29c7c is not true: in the path
> > hv_pci_probe() -> hv_pci_enter_d0() -> hv_pci_bus_exit(hdev, true): the
> > parameter "keep_devs" is true, so hv_pci_bus_exit() does *not* release the
> > child "struct hv_pci_dev *hpdev" that is created earlier in
> > pci_devices_present_work() -> new_pcichild_device().
> >
> > The commit d6af2ed29c7c was originally made in July 2020 for RHEL 7.7,
> > where the old version of hv_pci_bus_exit() was used; when the commit
> > was
> > rebased and merged into the upstream, people didn't notice that it's
> > not really necessary. The commit itself doesn't cause any issue, but it
> > makes hv_pci_probe() more complicated. Revert it to facilitate some
> > upcoming changes to hv_pci_probe().
> 
> If d6af2ed29c7c does not cause any issue this is not a fix and should be
> merged only with subsequent changes.

d6af2ed29c7c does not cause any functional issue, but it makes the code
less readable, and so I'd like to not merge this patch with patch 5 -- this way
people can easily know what the real change is in patch 5.