test/Parallel/ref_count.py

   1 #!/usr/bin/env python
   2 #
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  24
  25 __revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"
  26
  27 """
  28 Test for a specific race condition that used to stop a build cold when
  29 a Node's ref_count would get decremented past 0 and "disappear" from
  30 the Taskmaster's walk of the dependency graph.
  31
  32 Note that this test does not fail every time, but would at least fail
  33 more than 60%-70% of the time on the system(s) I tested.
  34
  35 The rather complicated set up here creates a condition where,
  36 after building four "object files" simultaneously while running with
  37 -j4, sets up a race condition amongst the three dependencies of the
  38 c6146/cpumanf.out file, where two of the dependencies are built at the
  39 same time (that is, by the same command) and one is built separately.
  40
  41 We used to detect Nodes that had been started but not finished building
  42 and just set the waiting ref_count to the number of Nodes.  In this case,
  43 if we got unlucky, we'd re-visit the Nodes for the two files first and
  44 set the ref_count to two *before* the command that built individual node
  45 completed and decremented the ref_count from two to one.  Then when the
  46 two files completed, we'd update the ref_count to 1 - 2 = -1, which would
  47 cause the Taskmaster to *not* "wake up" the Node because it's ref_count
  48 hadn't actually reached 0.
  49
  50 (The solution was to not set the ref_count, but to add to it only the
  51 Nodes that were, in fact, added to the waiting_parents lists of various
  52 child Nodes.)
  53 """
  54
  55 import TestSCons
  56
  57 _python_ = TestSCons._python_
  58
  59 test = TestSCons.TestSCons()
  60
  61 test.write('build.py', """\
  62 import sys
  63 import time
  64 args = sys.argv[1:]
  65 outputs = []
  66 while args:
  67     if args[0][0] != '-':
  68         break
  69     arg = args.pop(0)
  70     if arg == '-o':
  71         outputs.append(args.pop(0))
  72         continue
  73     if arg == '-s':
  74         time.sleep(int(args.pop(0)))
  75 contents = ''
  76 for ifile in args:
  77     with open(ifile, 'r') as ifp:
  78         contents = contents + ifp.read()
  79 for ofile in outputs:
  80     with open(ofile, 'w') as ofp:
  81         ofp.write('%s:  building from %s\\n' % (ofile, " ".join(args)))
  82         ofp.write(contents)
  83 """)
  84
  85 #
  86 #
  87 #
  88
  89 test.write('SConstruct', """\
  90 env = Environment()
  91 cmd = r'%(_python_)s build.py -o $TARGET $SOURCES'
  92 f1 = env.Command('c6416/cpumanf/file1.obj', 'file1.c', cmd)
  93 f2 = env.Command('c6416/cpumanf/file2.obj', 'file2.c', cmd)
  94 f3 = env.Command('c6416/cpumanf/file3.obj', 'file3.c', cmd)
  95 f4 = env.Command('c6416/cpumanf/file4.obj', 'file4.c', cmd)
  96 f5 = env.Command('c6416/cpumanf/file5.obj', 'file5.c', cmd)
  97 f6 = env.Command('c6416/cpumanf/file6.obj', 'file6.c', cmd)
  98
  99 objs = f1 + f2 + f3 + f4 + f5 + f6
 100
 101 btc = env.Command('build/target/cpumanf.out', 'c6416/cpumanf.out', cmd)
 102
 103 addcheck_obj = env.Command('addcheck.obj', 'addcheck.c', cmd)
 104
 105 addcheck_exe = env.Command('addcheck.exe', addcheck_obj, cmd)
 106
 107 cmd2 = r'%(_python_)s build.py -s 2 -o ${TARGETS[0]} -o ${TARGETS[1]} $SOURCES'
 108
 109 cksums = env.Command(['c6416/cpumanf_pre_cksum.out',
 110                      'c6416/cpumanf_pre_cksum.map'],
 111                     objs,
 112                     cmd2)
 113
 114 cpumanf_out = env.Command('c6416/cpumanf.out',
 115                           cksums + addcheck_exe,
 116                           cmd)
 117
 118 cpumanf = env.Alias('cpumanf', objs + btc)
 119
 120 env.Command('after.out', cpumanf, r'%(_python_)s build.py -o $TARGET after.in')
 121 """ % locals())
 122
 123 test.write('file1.c', "file1.c\n")
 124 test.write('file2.c', "file2.c\n")
 125 test.write('file3.c', "file3.c\n")
 126 test.write('file4.c', "file4.c\n")
 127 test.write('file5.c', "file5.c\n")
 128 test.write('file6.c', "file6.c\n")
 129
 130 test.write('addcheck.c', "addcheck.c\n")
 131
 132 test.write('after.in', "after.in\n")
 133
 134 test.run(arguments = '-j4 after.out')
 135
 136 test.must_match('after.out', """\
 137 after.out:  building from after.in
 138 after.in
 139 """, mode='r')
 140
 141 test.write('file5.c', "file5.c modified\n")
 142
 143 test.write('after.in', "after.in modified\n")
 144
 145 test.run(arguments = '-j4 after.out')
 146
 147 test.must_match('after.out', """\
 148 after.out:  building from after.in
 149 after.in modified
 150 """, mode='r')
 151
 152 test.pass_test()
 153
 154 # Local Variables:
 155 # tab-width:4
 156 # indent-tabs-mode:nil
 157 # End:
 158 # vim: set expandtab tabstop=4 shiftwidth=4: