Source code for cocotb.scheduler

#!/usr/bin/env python

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"""Coroutine scheduler.


FIXME: We have a problem here.  If a coroutine schedules a read-only but we
also have pending writes we have to schedule the ReadWrite callback before
the ReadOnly (and this is invalid, at least in Modelsim).
"""
import collections
import os
import sys
import logging
import threading

# Debug mode controlled by environment variables
if "COCOTB_ENABLE_PROFILING" in os.environ:
    import cProfile
    import pstats
    _profile = cProfile.Profile()
    _profiling = True
else:
    _profiling = False

# Sadly the Python standard logging module is very slow so it's better not to
# make any calls by testing a boolean flag first
if "COCOTB_SCHEDULER_DEBUG" in os.environ:
    _debug = True
else:
    _debug = False


import cocotb
import cocotb.decorators
from cocotb.triggers import (Trigger, GPITrigger, Timer, ReadOnly,
                             NextTimeStep, ReadWrite, Event, Join, NullTrigger)
from cocotb.log import SimLog
from cocotb.result import TestComplete, ReturnValue
from cocotb import _py_compat

# On python 3.7 onwards, `dict` is guaranteed to preserve insertion order.
# Since `OrderedDict` is a little slower that `dict`, we prefer the latter
# when possible.
if sys.version_info[:2] >= (3, 7):
    _ordered_dict = dict
else:
    _ordered_dict = collections.OrderedDict


class InternalError(RuntimeError):
    """ An error internal to scheduler. If you see this, report a bug! """
    pass


class profiling_context(object):
    """ Context manager that profiles its contents """
    def __enter__(self):
        _profile.enable()

    def __exit__(self, *excinfo):
        _profile.disable()


from cocotb import outcomes

class external_state(object):
    INIT = 0
    RUNNING = 1
    PAUSED = 2
    EXITED = 3

@cocotb.decorators.public
class external_waiter(object):

    def __init__(self):
        self._outcome = None
        self.thread = None
        self.event = Event()
        self.state = external_state.INIT
        self.cond = threading.Condition()
        self._log = SimLog("cocotb.external.thead.%s" % self.thread, id(self))

    @property
    def result(self):
        return self._outcome.get()

    def _propagate_state(self, new_state):
        with self.cond:
            if _debug:
                self._log.debug("Changing state from %d -> %d from %s" % (self.state, new_state, threading.current_thread()))
            self.state = new_state
            self.cond.notify()

    def thread_done(self):
        if _debug:
            self._log.debug("Thread finished from %s" % (threading.current_thread()))
        self._propagate_state(external_state.EXITED)

    def thread_suspend(self):
        self._propagate_state(external_state.PAUSED)

    def thread_start(self):
        if self.state > external_state.INIT:
            return

        if not self.thread.is_alive():
            self._propagate_state(external_state.RUNNING)
            self.thread.start()

    def thread_resume(self):
        self._propagate_state(external_state.RUNNING)

    def thread_wait(self):
        if _debug:
            self._log.debug("Waiting for the condition lock %s" % threading.current_thread())

        with self.cond:
            while self.state == external_state.RUNNING:
                self.cond.wait()

            if _debug:
                if self.state == external_state.EXITED:
                    self._log.debug("Thread %s has exited from %s" % (self.thread, threading.current_thread()))
                elif self.state == external_state.PAUSED:
                    self._log.debug("Thread %s has called yield from %s"  % (self.thread, threading.current_thread()))
                elif self.state == external_state.RUNNING:
                    self._log.debug("Thread %s is in RUNNING from %d"  % (self.thread, threading.current_thread()))

            if self.state == external_state.INIT:
                raise Exception("Thread %s state was not allowed from %s"  % (self.thread, threading.current_thread()))

        return self.state

[docs]class Scheduler(object): """The main scheduler. Here we accept callbacks from the simulator and schedule the appropriate coroutines. A callback fires, causing the :any:`react` method to be called, with the trigger that caused the callback as the first argument. We look up a list of coroutines to schedule (indexed by the trigger) and schedule them in turn. NB implementors should not depend on the scheduling order! Some additional management is required since coroutines can return a list of triggers, to be scheduled when any one of the triggers fires. To ensure we don't receive spurious callbacks, we have to un-prime all the other triggers when any one fires. Due to the simulator nuances and fun with delta delays we have the following modes: Normal mode - Callbacks cause coroutines to be scheduled - Any pending writes are cached and do not happen immediately ReadOnly mode - Corresponds to cbReadOnlySynch (VPI) or vhpiCbLastKnownDeltaCycle (VHPI). In this state we are not allowed to perform writes. Write mode - Corresponds to cbReadWriteSynch (VPI) or vhpiCbEndOfProcesses (VHPI) In this mode we play back all the cached write updates. We can legally transition from normal->write by registering a ReadWrite callback, however usually once a simulator has entered the ReadOnly phase of a given timestep then we must move to a new timestep before performing any writes. The mechanism for moving to a new timestep may not be consistent across simulators and therefore we provide an abstraction to assist with compatibility. Unless a coroutine has explicitly requested to be scheduled in ReadOnly mode (for example wanting to sample the finally settled value after all delta delays) then it can reasonably be expected to be scheduled during "normal mode" i.e. where writes are permitted. """ _MODE_NORMAL = 1 # noqa _MODE_READONLY = 2 # noqa _MODE_WRITE = 3 # noqa _MODE_TERM = 4 # noqa # Singleton events, recycled to avoid spurious object creation _next_time_step = NextTimeStep() _read_write = ReadWrite() _read_only = ReadOnly() _timer1 = Timer(1) def __init__(self): self.log = SimLog("cocotb.scheduler") if _debug: self.log.setLevel(logging.DEBUG) # Use OrderedDict here for deterministic behavior (gh-934) # A dictionary of pending coroutines for each trigger, # indexed by trigger self._trigger2coros = _ordered_dict() # A dictionary mapping coroutines to the trigger they are waiting for self._coro2trigger = _ordered_dict() # Our main state self._mode = Scheduler._MODE_NORMAL # A dictionary of pending writes self._writes = _ordered_dict() self._pending_coros = [] self._pending_triggers = [] self._pending_threads = [] self._pending_events = [] # Events we need to call set on once we've unwound self._terminate = False self._test = None self._main_thread = threading.current_thread() self._is_reacting = False self._write_coro_inst = None self._writes_pending = Event() @cocotb.decorators.coroutine def _do_writes(self): """ An internal coroutine that performs pending writes """ while True: yield self._writes_pending.wait() if self._mode != Scheduler._MODE_NORMAL: yield self._next_time_step yield self._read_write while self._writes: handle, value = self._writes.popitem() handle.setimmediatevalue(value) self._writes_pending.clear() def _check_termination(self): """ Handle a termination that causes us to move onto the next test. """ if self._terminate: if _debug: self.log.debug("Test terminating, scheduling Timer") if self._write_coro_inst is not None: self._write_coro_inst.kill() self._write_coro_inst = None for t in self._trigger2coros: t.unprime() if self._timer1.primed: self._timer1.unprime() self._timer1.prime(self._test_completed) self._trigger2coros = _ordered_dict() self._coro2trigger = _ordered_dict() self._terminate = False self._writes = _ordered_dict() self._writes_pending.clear() self._mode = Scheduler._MODE_TERM def _test_completed(self, trigger=None): """Called after a test and its cleanup have completed """ if _debug: self.log.debug("begin_test called with trigger: %s" % (str(trigger))) if _profiling: ps = pstats.Stats(_profile).sort_stats('cumulative') ps.dump_stats("test_profile.pstat") ctx = profiling_context() else: ctx = _py_compat.nullcontext() with ctx: self._mode = Scheduler._MODE_NORMAL if trigger is not None: trigger.unprime() # extract the current test, and clear it test = self._test self._test = None if test is None: raise InternalError("_test_completed called with no active test") if test._outcome is None: raise InternalError("_test_completed called with an incomplete test") # Issue previous test result if _debug: self.log.debug("Issue test result to regression object") # this may scheduler another test cocotb.regression_manager.handle_result(test) # if it did, make sure we handle the test completing self._check_termination()
[docs] def react(self, trigger): """ Called when a trigger fires. We ensure that we only start the event loop once, rather than letting it recurse. """ if self._is_reacting: # queue up the trigger, the event loop will get to it self._pending_triggers.append(trigger) return if self._pending_triggers: raise InternalError( "Expected all triggers to be handled but found {}" .format(self._pending_triggers) ) # start the event loop self._is_reacting = True try: self._event_loop(trigger) finally: self._is_reacting = False
def _event_loop(self, trigger): """ Run an event loop triggered by the given trigger. The loop will keep running until no further triggers fire. This should be triggered by only: * The beginning of a test, when there is no trigger to react to * A GPI trigger """ if _profiling: ctx = profiling_context() else: ctx = _py_compat.nullcontext() with ctx: # When a trigger fires it is unprimed internally if _debug: self.log.debug("Trigger fired: %s" % str(trigger)) # trigger.unprime() if self._mode == Scheduler._MODE_TERM: if _debug: self.log.debug("Ignoring trigger %s since we're terminating" % str(trigger)) return if trigger is self._read_only: self._mode = Scheduler._MODE_READONLY # Only GPI triggers affect the simulator scheduling mode elif isinstance(trigger, GPITrigger): self._mode = Scheduler._MODE_NORMAL # work through triggers one by one is_first = True self._pending_triggers.append(trigger) while self._pending_triggers: trigger = self._pending_triggers.pop(0) if not is_first and isinstance(trigger, GPITrigger): self.log.warning( "A GPI trigger occurred after entering react - this " "should not happen." ) assert False # this only exists to enable the warning above is_first = False # Scheduled coroutines may append to our waiting list so the first # thing to do is pop all entries waiting on this trigger. try: scheduling = self._trigger2coros.pop(trigger) except KeyError: # GPI triggers should only be ever pending if there is an # associated coroutine waiting on that trigger, otherwise it would # have been unprimed already if isinstance(trigger, GPITrigger): self.log.critical( "No coroutines waiting on trigger that fired: %s" % str(trigger)) trigger.log.info("I'm the culprit") # For Python triggers this isn't actually an error - we might do # event.set() without knowing whether any coroutines are actually # waiting on this event, for example elif _debug: self.log.debug( "No coroutines waiting on trigger that fired: %s" % str(trigger)) del trigger continue if _debug: debugstr = "\n\t".join([coro.__name__ for coro in scheduling]) if len(scheduling): debugstr = "\n\t" + debugstr self.log.debug("%d pending coroutines for event %s%s" % (len(scheduling), str(trigger), debugstr)) # This trigger isn't needed any more trigger.unprime() for coro in scheduling: if _debug: self.log.debug("Scheduling coroutine %s" % (coro.__name__)) self.schedule(coro, trigger=trigger) if _debug: self.log.debug("Scheduled coroutine %s" % (coro.__name__)) # Schedule may have queued up some events so we'll burn through those while self._pending_events: if _debug: self.log.debug("Scheduling pending event %s" % (str(self._pending_events[0]))) self._pending_events.pop(0).set() # remove our reference to the objects at the end of each loop, # to try and avoid them being destroyed at a weird time (as # happened in gh-957) del trigger del coro del scheduling # no more pending triggers self._check_termination() if _debug: self.log.debug("All coroutines scheduled, handing control back" " to simulator")
[docs] def unschedule(self, coro): """Unschedule a coroutine. Unprime any pending triggers""" # Unprime the trigger this coroutine is waiting on try: trigger = self._coro2trigger.pop(coro) except KeyError: # coroutine probably finished pass else: if coro in self._trigger2coros.setdefault(trigger, []): self._trigger2coros[trigger].remove(coro) if not self._trigger2coros[trigger]: trigger.unprime() del self._trigger2coros[trigger] assert self._test is not None if coro is self._test: if _debug: self.log.debug("Unscheduling test {}".format(coro)) if not self._terminate: self._terminate = True self.cleanup() elif Join(coro) in self._trigger2coros: self.react(Join(coro)) else: try: # throws an error if the background coroutine errored # and no one was monitoring it coro._outcome.get() except (TestComplete, AssertionError) as e: coro.log.info("Test stopped by this forked coroutine") outcome = outcomes.Error(e).without_frames(['unschedule', 'get']) self._test._force_outcome(outcome) except Exception as e: coro.log.error("Exception raised by this forked coroutine") outcome = outcomes.Error(e).without_frames(['unschedule', 'get']) self._test._force_outcome(outcome)
def save_write(self, handle, value): if self._mode == Scheduler._MODE_READONLY: raise Exception("Write to object {0} was scheduled during a read-only sync phase.".format(handle._name)) # TODO: we should be able to better keep track of when this needs to # be scheduled if self._write_coro_inst is None: self._write_coro_inst = self._do_writes() self.schedule(self._write_coro_inst) self._writes[handle] = value self._writes_pending.set() def _coroutine_yielded(self, coro, trigger): """Prime the trigger and update our internal mappings.""" self._coro2trigger[coro] = trigger trigger_coros = self._trigger2coros.setdefault(trigger, []) if coro is self._write_coro_inst: # Our internal write coroutine always runs before any user coroutines. # This preserves the behavior prior to the refactoring of writes to # this coroutine. trigger_coros.insert(0, coro) else: # Everything else joins the back of the queue trigger_coros.append(coro) if not trigger.primed: if trigger_coros != [coro]: # should never happen raise InternalError( "More than one coroutine waiting on an unprimed trigger") try: trigger.prime(self.react) except Exception as e: # discard the trigger we associated, it will never fire self._trigger2coros.pop(trigger) # replace it with a new trigger that throws back the exception error_trigger = NullTrigger(outcome=outcomes.Error(e)) self._coro2trigger[coro] = error_trigger self._trigger2coros[error_trigger] = [coro] # wake up the coroutines error_trigger.prime(self.react)
[docs] def queue(self, coroutine): """Queue a coroutine for execution""" self._pending_coros.append(coroutine)
[docs] def queue_function(self, coro): """Queue a coroutine for execution and move the containing thread so that it does not block execution of the main thread any longer. """ # We should be able to find ourselves inside the _pending_threads list matching_threads = [ t for t in self._pending_threads if t.thread == threading.current_thread() ] if len(matching_threads) == 0: raise RuntimeError("queue_function called from unrecognized thread") # Raises if there is more than one match. This can never happen, since # each entry always has a unique thread. t, = matching_threads @cocotb.coroutine def wrapper(): try: _outcome = outcomes.Value((yield coro)) except BaseException as e: _outcome = outcomes.Error(e) event.outcome = _outcome event.set() event = threading.Event() t.thread_suspend() self._pending_coros.append(wrapper()) # This blocks the calling external thread until the coroutine finishes event.wait() t.thread_resume() return event.outcome.get()
[docs] def run_in_executor(self, func, *args, **kwargs): """Run the coroutine in a separate execution thread and return a yieldable object for the caller. """ # Create a thread # Create a trigger that is called as a result of the thread finishing # Create an Event object that the caller can yield on # Event object set when the thread finishes execution, this blocks the # calling coroutine (but not the thread) until the external completes def execute_external(func, _waiter): _waiter._outcome = outcomes.capture(func, *args, **kwargs) if _debug: self.log.debug("Execution of external routine done %s" % threading.current_thread()) _waiter.thread_done() @cocotb.coroutine def wrapper(): waiter = external_waiter() thread = threading.Thread(group=None, target=execute_external, name=func.__name__ + "_thread", args=([func, waiter]), kwargs={}) waiter.thread = thread self._pending_threads.append(waiter) yield waiter.event.wait() ret = waiter.result # raises if there was an exception raise ReturnValue(ret) return wrapper()
[docs] def add(self, coroutine): """Add a new coroutine. Just a wrapper around self.schedule which provides some debug and useful error messages in the event of common gotchas. """ if isinstance(coroutine, cocotb.decorators.coroutine): raise TypeError( "Attempt to schedule a coroutine that hasn't started: {}.\n" "Did you forget to add parentheses to the @cocotb.test() " "decorator?" .format(coroutine) ) elif not isinstance(coroutine, cocotb.decorators.RunningCoroutine): raise TypeError( "Attempt to add a object of type {} to the scheduler, which " "isn't a coroutine: {!r}\n" "Did you forget to use the @cocotb.coroutine decorator?" .format(type(coroutine), coroutine) ) if _debug: self.log.debug("Adding new coroutine %s" % coroutine.__name__) self.schedule(coroutine) self._check_termination() return coroutine
[docs] def add_test(self, test_coro): """Called by the regression manager to queue the next test""" if self._test is not None: raise InternalError("Test was added while another was in progress") self._test = test_coro return self.add(test_coro)
# This collection of functions parses a trigger out of the object # that was yielded by a coroutine, converting `list` -> `Waitable`, # `Waitable` -> `RunningCoroutine`, `RunningCoroutine` -> `Trigger`. # Doing them as separate functions allows us to avoid repeating unencessary # `isinstance` checks. def _trigger_from_started_coro(self, result): # type: (cocotb.decorators.RunningCoroutine) -> Trigger if _debug: self.log.debug("Joining to already running coroutine: %s" % result.__name__) return result.join() def _trigger_from_unstarted_coro(self, result): # type: (cocotb.decorators.RunningCoroutine) -> Trigger self.queue(result) if _debug: self.log.debug("Scheduling nested coroutine: %s" % result.__name__) return result.join() def _trigger_from_waitable(self, result): # type: (cocotb.triggers.Waitable) -> Trigger return self._trigger_from_unstarted_coro(result._wait()) def _trigger_from_list(self, result): # type: (list) -> Trigger return self._trigger_from_waitable(cocotb.triggers.First(*result)) def _trigger_from_any(self, result): """Convert a yielded object into a Trigger instance""" # note: the order of these can significantly impact performance if isinstance(result, Trigger): return result if isinstance(result, cocotb.decorators.RunningCoroutine): if not result.has_started(): return self._trigger_from_unstarted_coro(result) else: return self._trigger_from_started_coro(result) if isinstance(result, list): return self._trigger_from_list(result) if isinstance(result, cocotb.triggers.Waitable): return self._trigger_from_waitable(result) raise TypeError( "Coroutine yielded an object of type {}, which the scheduler can't " "handle: {!r}\n" "Did you forget to decorate with @cocotb.coroutine?" .format(type(result), result) )
[docs] def schedule(self, coroutine, trigger=None): """Schedule a coroutine by calling the send method. Args: coroutine (cocotb.decorators.coroutine): The coroutine to schedule. trigger (cocotb.triggers.Trigger): The trigger that caused this coroutine to be scheduled. """ if trigger is None: send_outcome = outcomes.Value(None) else: send_outcome = trigger._outcome if _debug: self.log.debug("Scheduling with {}".format(send_outcome)) coro_completed = False try: result = coroutine._advance(send_outcome) if _debug: self.log.debug("Coroutine %s yielded %s (mode %d)" % (coroutine.__name__, str(result), self._mode)) except cocotb.decorators.CoroutineComplete as exc: if _debug: self.log.debug("Coroutine {} completed with {}".format( coroutine, coroutine._outcome )) coro_completed = True # this can't go in the else above, as that causes unwanted exception # chaining if coro_completed: self.unschedule(coroutine) return # Don't handle the result if we're shutting down if self._terminate: return try: result = self._trigger_from_any(result) except TypeError as exc: # restart this coroutine with an exception object telling it that # it wasn't allowed to yield that result = NullTrigger(outcome=outcomes.Error(exc)) self._coroutine_yielded(coroutine, result) # We do not return from here until pending threads have completed, but only # from the main thread, this seems like it could be problematic in cases # where a sim might change what this thread is. if self._main_thread is threading.current_thread(): for ext in self._pending_threads: ext.thread_start() if _debug: self.log.debug("Blocking from %s on %s" % (threading.current_thread(), ext.thread)) state = ext.thread_wait() if _debug: self.log.debug("Back from wait on self %s with newstate %d" % (threading.current_thread(), state)) if state == external_state.EXITED: self._pending_threads.remove(ext) self._pending_events.append(ext.event) # Handle any newly queued coroutines that need to be scheduled while self._pending_coros: self.add(self._pending_coros.pop(0))
def finish_test(self, exc): self._test.abort(exc)
[docs] def finish_scheduler(self, exc): """Directly call into the regression manager and end test once we return the sim will close us so no cleanup is needed. """ # If there is an error during cocotb initialization, self._test may not # have been set yet. Don't cause another Python exception here. if self._test: self.log.debug("Issue sim closedown result to regression object") self._test.abort(exc) cocotb.regression_manager.handle_result(self._test)
[docs] def cleanup(self): """Clear up all our state. Unprime all pending triggers and kill off any coroutines stop all externals. """ # copy since we modify this in kill items = list(self._trigger2coros.items()) # reversing seems to fix gh-928, although the order is still somewhat # arbitrary. for trigger, waiting in items[::-1]: for coro in waiting: if _debug: self.log.debug("Killing %s" % str(coro)) coro.kill() if self._main_thread is not threading.current_thread(): raise Exception("Cleanup() called outside of the main thread") for ext in self._pending_threads: self.log.warn("Waiting for %s to exit", ext.thread)