1. U NIVERSITY OF M ASSACHUSETTS, A MHERST Department of Computer Science Grace: Safe Multithreaded Programming for C/C++ Emery Berger University of Massachusetts, UPC/BSC www.cs.umass.edu/~emery

2. U NIVERSITY OF M ASSACHUSETTS, A MHERST Department of Computer Science

24. “”

30. race condition

35. atomicity violation

38. deadlock

42. order violation

44. sequential

47. race conditions

48. atomicity violations

49. race conditions atomicity violations deadlock

50. race conditions atomicity violations deadlock order violations

52. Grace race conditions atomicity violations deadlock order violations

53. race conditions atomicity violations deadlock order violations Grace

54. race conditions atomicity violations deadlock order violations sequential Grace

55. % g++ myprog.cpp –lpthread –o myprog

56. Grace % g++ myprog.cpp –lgrace –o myprog

57. Grace % g++ myprog.cpp –lgrace –o myprog sequential

58. Grace % g++ myprog.cpp –lgrace –o myprog sequential race conditions atomicity violations deadlock order violations

59. Grace % g++ myprog.cpp –lgrace –o myprog sequential race conditions atomicity violations deadlock order violations

60. Safe and (usually) fast…

61. benign race

62. Grace sequential +?1.

63. Grace sequential +?1. 2.

64. Grace sequential +?1. 2. 3.

65. sequential +?1.

66. sequential +?1. t1 = spawn f(x); t2 = spawn g(y); sync;

67. sequential +?1. t1 = spawn f(x); t2 = spawn g(y); sync; spawn f(x)

68. sequential +?1. t1 = spawn f(x); t2 = spawn g(y); sync; f(x) spawn f(x)

69. sequential +?1. t1 = spawn f(x); t2 = spawn g(y); sync; f(x) spawn f(x) spawn g(y)

70. sequential +?1. t1 = spawn f(x); t2 = spawn g(y); sync; f(x) g(y) spawn f(x) spawn g(y)

71. sequential +?1. t1 = spawn f(x); t2 = spawn g(y); sync; f(x) g(y) spawn f(x) spawn g(y) sync

72. sequential +?1. t1 = spawn f(x); t2 = spawn g(y); sync; f(x) g(y) spawn f(x) spawn g(y) sync

73. sequential +?1. t1 = spawn f(x); t2 = spawn g(y); sync; f(x) g(y) spawn f(x) spawn g(y) sync left-to-right, depth-first ordering

74. sequential +?1. t1 = spawn f(x); t2 = spawn g(y); sync; f(x) g(y)

75. sequential +?1. t1 = spawn f(x); t2 = spawn g(y); sync; f(x) g(y) “”

76. sequential +?1. f(x) g(y) “”

77. sequential +?1. f(x) g(y) “” race conditions atomicity violations deadlock order violations

78. sequential +?1. f(x) g(y) “” race conditions atomicity violations deadlock order violations

79. sequential +?1. f(x) g(y) “” race conditions atomicity violations deadlock order violations

80. sequential +?1. f(x) g(y) “” race conditions atomicity violations deadlock order violations

81. sequential +?1. f(x) g(y) “” race conditions atomicity violations deadlock order violations

82. sequential +?1. f(x) g(y) “” race conditions atomicity violations deadlock order violations

83. sequential +?1. f(x) g(y) “” race conditions atomicity violations deadlock order violations

84. sequential +?1. f(x) g(y) “”

85. sequential +?1. f(x) g(y) “”

86. sequential +?1. f(x) g(y) “”

87. sequential +?1. f(x) g(y) “”

88. sequential +?1. f(x) g(y) “”

89. sequential +?1. f(x) g(y) “” Fork-join (e.g., map-reduce, Cilk, TBB…)

90. ? 2. What’s under the hood?

91. ? 2. “Magic!”

92. ? 2. +

93. ?

94. ? t1 = spawn f(x); t2 = spawn g(y); sync;

95. ? 2. t1 = spawn f(x); t2 = spawn g(y); sync; if (!fork()) f(x); if (!fork()) g(y); // check;

96. ? 2. if (!fork()) f(x); if (!fork()) g(y); // check; f(x) g(y) spawn f(x) spawn g(y) sync

97. ? 2. if (!fork()) f(x); if (!fork()) g(y); // check; f(x) g(y) spawn f(x) spawn g(y) sync

98. ? 2. if (!fork()) f(x); if (!fork()) g(y); // check; f(x) g(y) spawn f(x) spawn g(y) sync Note: Nested threads ok

99. ? 2. f(x) g(y) spawn f(x) spawn g(y) sync mmap

100. ? 2. f(x) g(y) spawn f(x) spawn g(y) sync mmap

101. ? 2. f(x) g(y) spawn f(x) spawn g(y) sync mmap

102. ? 2. f(x) g(y) spawn f(x) spawn g(y) sync

103. ? 2. f(x) g(y) spawn f(x) spawn g(y) sync 1

104. ? 2. f(x) g(y) spawn f(x) spawn g(y) sync 1 2

105. ? 2. scalable heap + aligned globals I/O (buffering + ordering)

106. 3. More detailed results…

110. Grace sequential race conditions atomicity violations deadlock order violations

111. Grace sequential race conditions atomicity violations deadlock order violations

112. Grace sequential race conditions atomicity violations deadlock order violations

113. Grace sequential race conditions atomicity violations deadlock order violations % g++ myprog.cpp –lgrace –o myprog

114. “Moltes gràcies”

115. U NIVERSITY OF M ASSACHUSETTS, A MHERST Department of Computer Science ? 2.

116. U NIVERSITY OF M ASSACHUSETTS, A MHERST Department of Computer Science ? 2.

117. U NIVERSITY OF M ASSACHUSETTS, A MHERST Department of Computer Science ? 2. +

118. U NIVERSITY OF M ASSACHUSETTS, A MHERST Department of Computer Science ? 2. ++