On 2021-05-11 10:05 a.m., Don Dutile wrote: > On 4/8/21 1:01 PM, Logan Gunthorpe wrote: >> In order to use upstream_bridge_distance_warn() from a dma_map function, >> it must not sleep. However, pci_get_slot() takes the pci_bus_sem so it >> might sleep. >> >> In order to avoid this, try to get the host bridge's device from >> bus->self, and if that is not set, just get the first element in the >> device list. It should be impossible for the host bridge's device to >> go away while references are held on child devices, so the first element >> should not be able to change and, thus, this should be safe. > Bjorn: > Why wouldn't (shouldn't?) the bus->self field be set for a host bridge device? > Should this situation be repaired in the host-brige config/setup code elsewhere in the kernel. > ... and here, a check-and-fail with info of what doesn't have it setup (another new pci function to do the check & prinfo), so it can point to the offending host-bridge, and thus, the code that needs to be updated? I've dropped the bus->self thing in v2. Seems bus->self is explicitly unset for root bridges. There's remnants in the pci code that used to check bus->self to see if the bridge is the root bridge. I tried setting bus->self with the pci device of the root bridge but that just caused my machine not to boot and I didn't dig any further. Logan
