On Wed, Dec 13, 2023 at 2:01 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: > > On Wed, Dec 13, 2023 at 1:36 AM Igor Mammedov <imammedo@xxxxxxxxxx> wrote: > > > > 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> > > Signed-off-by: Igor Mammedov <imammedo@xxxxxxxxxx> > > --- > > drivers/pci/hotplug/acpiphp_glue.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c > > index 601129772b2d..6b11609927d6 100644 > > --- a/drivers/pci/hotplug/acpiphp_glue.c > > +++ b/drivers/pci/hotplug/acpiphp_glue.c > > @@ -722,7 +722,9 @@ static void acpiphp_check_bridge(struct acpiphp_bridge *bridge) > > trim_stale_devices(dev); > > > > /* configure all functions */ > > - enable_slot(slot, true); > > + if (slot->flags != SLOT_ENABLED) { > > + enable_slot(slot, true); > > + } > > Shouldn't this be following the acpiphp_enable_slot() pattern, that is > > if (!(slot->flags & SLOT_ENABLED)) > enable_slot(slot, true); > > Also the braces are redundant. I'll fix up on respin if Bjorn is fine with the approach in general. Patches need respin anyways to fix botched up white spacing. > > > } else { > > disable_slot(slot); > > } > > -- >