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

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

“”

race condition

atomicity violation

deadlock

order violation

sequential

race conditions

atomicity violations

race conditions atomicity violations deadlock

race conditions atomicity violations deadlock order violations

Grace race conditions atomicity violations deadlock order violations

race conditions atomicity violations deadlock order violations Grace

race conditions atomicity violations deadlock order violations sequential Grace

% g++ myprog.cpp –lpthread –o myprog

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

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

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

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

Safe and (usually) fast…

benign race

Grace sequential +?1.

Grace sequential +?1. 2.

Grace sequential +?

sequential +?1.

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

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

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

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

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

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

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

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

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

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

sequential +?1. f(x) g(y) “”

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

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

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

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

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

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

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

sequential +?1. f(x) g(y) “”

sequential +?1. f(x) g(y) “”

sequential +?1. f(x) g(y) “”

sequential +?1. f(x) g(y) “”

sequential +?1. f(x) g(y) “”

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

? 2. What’s under the hood?

? 2. “Magic!”

? 2. +

?

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

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

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

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

? 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

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

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

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

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

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

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

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

3. More detailed results…

Grace sequential race conditions atomicity violations deadlock order violations

Grace sequential race conditions atomicity violations deadlock order violations

Grace sequential race conditions atomicity violations deadlock order violations

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

“Moltes gràcies”

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

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

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

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