1

#!/usr/bin/env python

     2

# -*- coding: utf-8 -*-

     3

     4

# This file is part of Beremiz runtime.

     5

#

     6

# Copyright (C) 2018: Edouard TISSERANT

     7

#

     8

# See COPYING.Runtime file for copyrights details.

     9

    10

from __future__ import absolute_import

    11

import sys

    12

import six

    13

import thread

    14

from threading import Lock, Condition

    15

    16

    17

class job(object):

    18

    """

    19

    job to be executed by a worker

    20

    """

    21

    def __init__(self, call, *args, **kwargs):

    22

        self.job = (call, args, kwargs)

    23

        self.result = None

    24

        self.success = False

    25

        self.exc_info = None

    26

    27

    def do(self):

    28

        """

    29

        do the job by executing the call, and deal with exceptions

    30

        """

    31

        try:

    32

            call, args, kwargs = self.job

    33

            self.result = call(*args, **kwargs)

    34

            self.success = True

    35

        except Exception:

    36

            self.success = False

    37

            self.exc_info = sys.exc_info()

    38

    39

    40

class worker(object):

    41

    """

    42

    serialize main thread load/unload of PLC shared objects

    43

    """

    44

    def __init__(self):

    45

        # Only one job at a time

    46

        self._finish = False

    47

        self._threadID = None

    48

        self.mutex = Lock()

    49

        self.todo = Condition(self.mutex)

    50

        self.done = Condition(self.mutex)

    51

        self.free = Condition(self.mutex)

    52

        self.job = None

    53

    54

    def runloop(self, *args, **kwargs):

    55

        """

    56

        meant to be called by worker thread (blocking)

    57

        """

    58

        self._threadID = thread.get_ident()

    59

        self.mutex.acquire()

    60

        if args or kwargs:

    61

            _job = job(*args, **kwargs)

    62

            _job.do()

    63

            if _job.success:

    64

                # result is ignored

    65

                pass

    66

            else:

    67

                raise _job.exc_info[0], _job.exc_info[1], _job.exc_info[2]

    68

        while not self._finish:

    69

            self.todo.wait()

    70

            if self.job is not None:

    71

                self.job.do()

    72

                self.done.notify()

    73

            else:

    74

                self.free.notify()

    75

        self.mutex.release()

    76

    77

    def call(self, *args, **kwargs):

    78

        """

    79

        creates a job, execute it in worker thread, and deliver result.

    80

        if job execution raise exception, re-raise same exception

    81

        meant to be called by non-worker threads, but this is accepted.

    82

        blocking until job done

    83

        """

    84

    85

        _job = job(*args, **kwargs)

    86

    87

        if self._threadID == thread.get_ident():

    88

            # if caller is worker thread execute immediately

    89

            _job.do()

    90

        else:

    91

            # otherwise notify and wait for completion

    92

            self.mutex.acquire()

    93

    94

            while self.job is not None:

    95

                self.free.wait()

    96

    97

            self.job = _job

    98

            self.todo.notify()

    99

            self.done.wait()

   100

            _job = self.job

   101

            self.job = None

   102

            self.mutex.release()

   103

   104

        if _job.success:

   105

            return _job.result

   106

        else:

   107

            exc_type = _job.exc_info[0]

   108

            exc_value = _job.exc_info[1]

   109

            exc_traceback = _job.exc_info[2]

   110

            six.reraise(exc_type, exc_value, exc_traceback)

   111

   112

    def quit(self):

   113

        """

   114

        unblocks main thread, and terminate execution of runloop()

   115

        """

   116

        # mark queue

   117

        self._finish = True

   118

        self.mutex.acquire()

   119

        self.job = None

   120

        self.todo.notify()

   121

        self.mutex.release()