summaryrefslogtreecommitdiff
path: root/lib/thread.rb
blob: e3aeed19fe023ebca069e6c6f9f6e9fe5bd62b69 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
#
#               thread.rb - thread support classes
#                       by Yukihiro Matsumoto <matz@netlab.co.jp>
#
# Copyright (C) 2001  Yukihiro Matsumoto
# Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
# Copyright (C) 2000  Information-technology Promotion Agency, Japan
#

unless defined? Thread
  raise "Thread not available for this ruby interpreter"
end

unless defined? ThreadError
  class ThreadError < StandardError
  end
end

if $DEBUG
  Thread.abort_on_exception = true
end

#
# ConditionVariable objects augment class Mutex. Using condition variables,
# it is possible to suspend while in the middle of a critical section until a
# resource becomes available.
#
# Example:
#
#   require 'thread'
#
#   mutex = Mutex.new
#   resource = ConditionVariable.new
#
#   a = Thread.new {
#     mutex.synchronize {
#       # Thread 'a' now needs the resource
#       resource.wait(mutex)
#       # 'a' can now have the resource
#     }
#   }
#
#   b = Thread.new {
#     mutex.synchronize {
#       # Thread 'b' has finished using the resource
#       resource.signal
#     }
#   }
#
class ConditionVariable
  #
  # Creates a new ConditionVariable
  #
  def initialize
    @waiters = []
    @waiters_mutex = Mutex.new
  end

  #
  # Releases the lock held in +mutex+ and waits; reacquires the lock on wakeup.
  #
  # If +timeout+ is given, this method returns after +timeout+ seconds passed,
  # even if no other thread doesn't signal.
  #
  def wait(mutex, timeout=nil)
    Thread.async_interrupt_timing(StandardError => :defer) do
      begin
        Thread.async_interrupt_timing(StandardError => :on_blocking) do
          @waiters_mutex.synchronize do
            @waiters.push(Thread.current)
          end
          mutex.sleep timeout
        end
      ensure
        @waiters_mutex.synchronize do
          @waiters.delete(Thread.current)
        end
      end
    end
    self
  end

  #
  # Wakes up the first thread in line waiting for this lock.
  #
  def signal
    Thread.async_interrupt_timing(RuntimeError => :on_blocking) do
      begin
        t = @waiters_mutex.synchronize {@waiters.shift}
        t.run if t
      rescue ThreadError
        retry # t was alread dead?
      end
    end
    self
  end

  #
  # Wakes up all threads waiting for this lock.
  #
  def broadcast
    Thread.async_interrupt_timing(RuntimeError => :on_blocking) do
      waiters0 = nil
      @waiters_mutex.synchronize do
        waiters0 = @waiters.dup
        @waiters.clear
      end
      for t in waiters0
        begin
          t.run
        rescue ThreadError
        end
      end
    end
    self
  end
end

#
# This class provides a way to synchronize communication between threads.
#
# Example:
#
#   require 'thread'
#
#   queue = Queue.new
#
#   producer = Thread.new do
#     5.times do |i|
#       sleep rand(i) # simulate expense
#       queue << i
#       puts "#{i} produced"
#     end
#   end
#
#   consumer = Thread.new do
#     5.times do |i|
#       value = queue.pop
#       sleep rand(i/2) # simulate expense
#       puts "consumed #{value}"
#     end
#   end
#
#   consumer.join
#
class Queue
  #
  # Creates a new queue.
  #
  def initialize
    @que = []
    @que.taint          # enable tainted communication
    @num_waiting = 0
    self.taint
    @mutex = Mutex.new
    @cond = ConditionVariable.new
  end

  #
  # Pushes +obj+ to the queue.
  #
  def push(obj)
    Thread.async_interrupt_timing(StandardError => :on_blocking) do
      @mutex.synchronize do
        @que.push obj
        @cond.signal
      end
    end
  end

  #
  # Alias of push
  #
  alias << push

  #
  # Alias of push
  #
  alias enq push

  #
  # Retrieves data from the queue.  If the queue is empty, the calling thread is
  # suspended until data is pushed onto the queue.  If +non_block+ is true, the
  # thread isn't suspended, and an exception is raised.
  #
  def pop(non_block=false)
    Thread.async_interrupt_timing(StandardError => :on_blocking) do
      @mutex.synchronize do
        while true
          if @que.empty?
            if non_block
              raise ThreadError, "queue empty"
            else
              begin
                @num_waiting += 1
                @cond.wait @mutex
              ensure
                @num_waiting -= 1
              end
            end
          else
            return @que.shift
          end
        end
      end
    end
  end

  #
  # Alias of pop
  #
  alias shift pop

  #
  # Alias of pop
  #
  alias deq pop

  #
  # Returns +true+ if the queue is empty.
  #
  def empty?
    @que.empty?
  end

  #
  # Removes all objects from the queue.
  #
  def clear
    @que.clear
  end

  #
  # Returns the length of the queue.
  #
  def length
    @que.length
  end

  #
  # Alias of length.
  #
  alias size length

  #
  # Returns the number of threads waiting on the queue.
  #
  def num_waiting
    @num_waiting
  end
end

#
# This class represents queues of specified size capacity.  The push operation
# may be blocked if the capacity is full.
#
# See Queue for an example of how a SizedQueue works.
#
class SizedQueue < Queue
  #
  # Creates a fixed-length queue with a maximum size of +max+.
  #
  def initialize(max)
    raise ArgumentError, "queue size must be positive" unless max > 0
    @max = max
    @enque_cond = ConditionVariable.new
    @num_enqueue_waiting = 0
    super()
  end

  #
  # Returns the maximum size of the queue.
  #
  def max
    @max
  end

  #
  # Sets the maximum size of the queue.
  #
  def max=(max)
    raise ArgumentError, "queue size must be positive" unless max > 0

    @mutex.synchronize do
      if max <= @max
        @max = max
      else
        diff = max - @max
        @max = max
        diff.times do
          @enque_cond.signal
        end
      end
    end
    max
  end

  #
  # Pushes +obj+ to the queue.  If there is no space left in the queue, waits
  # until space becomes available.
  #
  def push(obj)
    Thread.async_interrupt_timing(RuntimeError => :on_blocking) do
      @mutex.synchronize do
        while true
          break if @que.length < @max
          @num_enqueue_waiting += 1
          begin
            @enque_cond.wait @mutex
          ensure
            @num_enqueue_waiting -= 1
          end
        end

        @que.push obj
        @cond.signal
      end
    end
  end

  #
  # Alias of push
  #
  alias << push

  #
  # Alias of push
  #
  alias enq push

  #
  # Retrieves data from the queue and runs a waiting thread, if any.
  #
  def pop(*args)
    retval = super
    @mutex.synchronize do
      if @que.length < @max
        @enque_cond.signal
      end
    end
    retval
  end

  #
  # Alias of pop
  #
  alias shift pop

  #
  # Alias of pop
  #
  alias deq pop

  #
  # Returns the number of threads waiting on the queue.
  #
  def num_waiting
    @num_waiting + @num_enqueue_waiting
  end
end

# Documentation comments:
#  - How do you make RDoc inherit documentation from superclass?