• Nicholas Bellinger's avatar
    target: Fix percpu_ref_put race in transport_lun_remove_cmd · 5259a06e
    Nicholas Bellinger authored
    This patch fixes a percpu_ref_put race for se_lun->lun_ref in
    transport_lun_remove_cmd() where ->lun_ref could end up being
    put more than once per command via different target completion
    and fabric release contexts.
    It adds a cmpxchg() for se_cmd->lun_ref_active to ensure that
    percpu_ref_put() is only ever called once per se_cmd.
    This bug was manifesting itself as a LUN shutdown regression
    bug in >= v3.13 code, where percpu_ref_kill() would end up
    hanging indefinately due to the incorrect percpu_ref count.
    (Change se_cmd->lun_ref_active from bool -> int to force at
     least a 4-byte cmpxchg with MIPS ll/sc ins. - Fengguang)
    Reported-by: default avatarTommy Apel <tommyapeldk@gmail.com>
    Cc: Tommy Apel <tommyapeldk@gmail.com>
    Cc: <stable@vger.kernel.org> #3.13+
    Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
target_core_base.h 26 KB