author | Sverre Rabbelier <srabbelier@gmail.com> |
Sun, 08 Mar 2009 16:26:17 +0000 | |
changeset 1751 | 17c7a7a48dc7 |
parent 54 | 03e267d67478 |
permissions | -rw-r--r-- |
54
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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1 |
""" |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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|
2 |
Synchronization primitives: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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3 |
|
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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4 |
- reader-writer lock (preference to writers) |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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5 |
|
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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6 |
(Contributed to Django by eugene@lazutkin.com) |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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7 |
""" |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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8 |
|
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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9 |
try: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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10 |
import threading |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
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11 |
except ImportError: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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12 |
import dummy_threading as threading |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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13 |
|
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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14 |
class RWLock: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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15 |
""" |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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|
16 |
Classic implementation of reader-writer lock with preference to writers. |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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17 |
|
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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|
18 |
Readers can access a resource simultaneously. |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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19 |
Writers get an exclusive access. |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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20 |
|
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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21 |
API is self-descriptive: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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22 |
reader_enters() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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23 |
reader_leaves() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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24 |
writer_enters() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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25 |
writer_leaves() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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|
26 |
""" |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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|
27 |
def __init__(self): |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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28 |
self.mutex = threading.RLock() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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29 |
self.can_read = threading.Semaphore(0) |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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|
30 |
self.can_write = threading.Semaphore(0) |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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31 |
self.active_readers = 0 |
03e267d67478
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Todd Larsen <tlarsen@google.com>
parents:
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32 |
self.active_writers = 0 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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33 |
self.waiting_readers = 0 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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|
34 |
self.waiting_writers = 0 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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35 |
|
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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|
36 |
def reader_enters(self): |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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37 |
self.mutex.acquire() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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|
38 |
try: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
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39 |
if self.active_writers == 0 and self.waiting_writers == 0: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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|
40 |
self.active_readers += 1 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
41 |
self.can_read.release() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
42 |
else: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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|
43 |
self.waiting_readers += 1 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
44 |
finally: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
45 |
self.mutex.release() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
46 |
self.can_read.acquire() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
47 |
|
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
48 |
def reader_leaves(self): |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
49 |
self.mutex.acquire() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
50 |
try: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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51 |
self.active_readers -= 1 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
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52 |
if self.active_readers == 0 and self.waiting_writers != 0: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
53 |
self.active_writers += 1 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
54 |
self.waiting_writers -= 1 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
55 |
self.can_write.release() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
56 |
finally: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
57 |
self.mutex.release() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
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58 |
|
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
59 |
def writer_enters(self): |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
60 |
self.mutex.acquire() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
61 |
try: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
62 |
if self.active_writers == 0 and self.waiting_writers == 0 and self.active_readers == 0: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
63 |
self.active_writers += 1 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
64 |
self.can_write.release() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
65 |
else: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
66 |
self.waiting_writers += 1 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
67 |
finally: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
68 |
self.mutex.release() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
69 |
self.can_write.acquire() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
70 |
|
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
71 |
def writer_leaves(self): |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
72 |
self.mutex.acquire() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
73 |
try: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
74 |
self.active_writers -= 1 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
75 |
if self.waiting_writers != 0: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
76 |
self.active_writers += 1 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
77 |
self.waiting_writers -= 1 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
78 |
self.can_write.release() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
79 |
elif self.waiting_readers != 0: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
80 |
t = self.waiting_readers |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
81 |
self.waiting_readers = 0 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
82 |
self.active_readers += t |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
83 |
while t > 0: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
84 |
self.can_read.release() |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
85 |
t -= 1 |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
86 |
finally: |
03e267d67478
Major reorganization of the soc svn repo, to merge into a single App Engine
Todd Larsen <tlarsen@google.com>
parents:
diff
changeset
|
87 |
self.mutex.release() |