On Wed, 13 Dec 2023 10:47:27 +0100
Fiona Ebner <f.ebner@xxxxxxxxxxx> wrote:
> Am 13.12.23 um 01:36 schrieb Igor Mammedov:
> > When SCSI_SCAN_ASYNC is enabled (either via config or via cmd line),
> > adding device to bus and enabling it will kick in async host scan
> >
> > scsi_scan_host+0x21/0x1f0
> > virtscsi_probe+0x2dd/0x350
> > ..
> > driver_probe_device+0x19/0x80
> > ...
> > driver_probe_device+0x19/0x80
> > pci_bus_add_device+0x53/0x80
> > pci_bus_add_devices+0x2b/0x70
> > ...
> >
> > which will schedule a job for async scan. That however breaks
> > if there are more than one SCSI host behind bridge, since
> > acpiphp_check_bridge() will walk over all slots and try to
> > enable each of them regardless of whether they were already
> > enabled.
> > As result the bridge might be reconfigured several times
> > and trigger following sequence:
> >
> > [cpu 0] acpiphp_check_bridge()
> > [cpu 0] enable_slot(a)
> > [cpu 0] configure bridge
> > [cpu 0] pci_bus_add_devices() -> scsi_scan_host(a1)
> > [cpu 0] enable_slot(b)
> > ...
> > [cpu 1] do_scsi_scan_host(a1) <- async jib scheduled for slot a
> > ...
> > [cpu 0] configure bridge <- temporaly disables bridge
> >
> > and cause do_scsi_scan_host() failure.
> > The same race affects SHPC (but it manages to avoid hitting the race due to
> > 1sec delay when enabling slot).
> > To cover case of single device hotplug (at a time) do not attempt to
> > enable slot that have already been enabled.
> >
> > Fixes: 40613da52b13 ("PCI: acpiphp: Reassign resources on bridge if necessary")
> > Reported-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
> > Reported-by: iona Ebner <f.ebner@xxxxxxxxxxx>
>
> Missing an F here ;)
Sorry for copypaste mistake, I'll fix it up on the next submission.
>
> > Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx>
>
> Thank you! Works for me:
>
> Tested-by: Fiona Ebner <f.ebner@xxxxxxxxxxx>
>
