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from m5.SimObject import SimObject
from m5.params import *


class ThreadBridge(SimObject):
    """Bridge for SimObjects from different threads (EventQueues)

    When two SimObjects running on two separate threads (EventQueues), an
    access from one side to the other side could easily cause event scheduled
    on the wrong event queue.

    ThreadBridge is used to migrate the EventQueue to the one used by
    ThreadBridge itself before sending transation to the other side to avoid
    the issue. The receiver side is expected to use the same EventQueue that
    the ThreadBridge is using.

    Given that this is only used for simulation speed accelerating, only the
    atomic and functional access are supported.

    Example:

    sys.initator = Initiator(eventq_index=0)
    sys.target = Target(eventq_index=1)
    sys.bridge = ThreadBridge(eventq_index=1)

    sys.initator.out_port = sys.bridge.in_port
    sys.bridge.out_port = sys.target.in_port
    """

    type = "ThreadBridge"
    cxx_header = "mem/thread_bridge.hh"
    cxx_class = "gem5::ThreadBridge"

    in_port = ResponsePort("Incoming port")
    out_port = RequestPort("Outgoing port")