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References: <20231213003614.1648343-1-imammedo@redhat.com> <20231213181115.GA1050010@bhelgaas>
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From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Wed, 13 Dec 2023 19:12:51 +0100
Message-ID: <CAJZ5v0iCwpqRXGFvQ8xtEoK=RaJdb-gnwkWezR7WSX7R_oyFYw@mail.gmail.com>
Subject: Re: [RFC 0/2] PCI: acpiphp: workaround race between hotplug and
 SCSI_SCAN_ASYNC job
To:     Bjorn Helgaas <helgaas@kernel.org>
Cc:     Igor Mammedov <imammedo@redhat.com>, linux-kernel@vger.kernel.org,
        Dongli Zhang <dongli.zhang@oracle.com>,
        linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org,
        mst@redhat.com, rafael@kernel.org, lenb@kernel.org,
        bhelgaas@google.com, mika.westerberg@linux.intel.com,
        boris.ostrovsky@oracle.com, joe.jin@oracle.com,
        stable@vger.kernel.org, Fiona Ebner <f.ebner@proxmox.com>,
        Thomas Lamprecht <t.lamprecht@proxmox.com>
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On Wed, Dec 13, 2023 at 7:11 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> On Wed, Dec 13, 2023 at 01:36:12AM +0100, Igor Mammedov wrote:
> > Hacks to mask a race between HBA scan job and bridge re-configuration(s)
> > during hotplug.
> >
> > I don't like it a bit but it something that could be done quickly
> > and solves problems that were reported.
>
> I agree, I don't like it either.  Adding a 1s delay doesn't address
> the real problem, and putting in a band-aid like this means the real
> problem would likely never be addressed.
>
> At this point the best option I see is to revert these:
>
>   cc22522fd55e2 ("PCI: acpiphp: Use pci_assign_unassigned_bridge_resources() only for non-root bus")
>   40613da52b13f ("PCI: acpiphp: Reassign resources on bridge if necessary")
>
> I hate the fact that reverting them would mean the root bus hotplug
> and ACPI bus check notifications would become issues again.
>
> But keeping these commits even though they add a new different problem
> that breaks things for somebody else seems worse to me.

Agreed.