• Jan Kiszka's avatar
    PCI: Rework config space blocking services · fb51ccbf
    Jan Kiszka authored
    pci_block_user_cfg_access was designed for the use case that a single
    context, the IPR driver, temporarily delays user space accesses to the
    config space via sysfs. This assumption became invalid by the time
    pci_dev_reset was added as locking instance. Today, if you run two loops
    in parallel that reset the same device via sysfs, you end up with a
    kernel BUG as pci_block_user_cfg_access detect the broken assumption.
    
    This reworks the pci_block_user_cfg_access to a sleeping service
    pci_cfg_access_lock and an atomic-compatible variant called
    pci_cfg_access_trylock. The former not only blocks user space access as
    before but also waits if access was already locked. The latter service
    just returns false in this case, allowing the caller to resolve the
    conflict instead of raising a BUG.
    
    Adaptions of the ipr driver were originally written by Brian King.
    Acked-by: 's avatarBrian King <brking@linux.vnet.ibm.com>
    Acked-by: 's avatarMichael S. Tsirkin <mst@redhat.com>
    Signed-off-by: 's avatarJan Kiszka <jan.kiszka@siemens.com>
    Signed-off-by: 's avatarJesse Barnes <jbarnes@virtuousgeek.org>
    fb51ccbf
access.c 11.2 KB