Grace Safe Multithreaded Programming for CC Emery Berger

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

UNIVERSITY OF MASSACHUSETTS , AMHERST • Department of Computer Science

UNIVERSITY OF MASSACHUSETTS , AMHERST • Department of Computer Science

“ UNIVERSITY OF MASSACHUSETTS , AMHERST • Department of Computer Science ”

race condition

atomicity violation

deadlock

order violation

sequential

race conditions

race conditions atomicity violations

race conditions atomicity violations deadlock

race conditions atomicity violations deadlock order violations

race conditions Grace atomicity violations deadlock order violations

race conditions Grace 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 sequential –o myprog

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

Safe and (usually) fast…

benign race

Grace 1. sequential + ?

Grace 1. 2. sequential + ?

Grace 1. 2. 3. sequential + ?

1. sequential + ?

1. sequential t 1 = spawn f(x); t 2 = spawn g(y); sync; + ?

1. sequential + ? spawn f(x) t 1 = spawn f(x); t 2 = spawn g(y); sync;

1. sequential + ? spawn f(x) t 1 = spawn f(x); t 2 = spawn g(y); sync; f(x)

1. sequential + ? spawn f(x) t 1 = spawn f(x); t 2 = spawn g(y); sync; f(x) spawn g(y)

1. sequential + ? spawn f(x) t 1 = spawn f(x); t 2 = spawn g(y); sync; f(x) spawn g(y) sync g(y)

1. sequential + ? spawn f(x) t 1 = spawn f(x); t 2 = spawn g(y); sync; f(x) spawn g(y) left-to-right, depth-first ordering sync

1. sequential + ? f(x) t 1 = spawn f(x); t 2 = spawn g(y); sync; g(y)

1. sequential t 1 = spawn f(x); t 2 = spawn g(y); sync; + ? “ f(x) g(y) ”

1. “ sequential f(x) g(y) ” + ?

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

1. “ sequential f(x) g(y) ” + ?

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

2. ? What’s under the hood?

2. ? “Magic!”

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

2. ? t 1 = spawn f(x); t 2 = spawn g(y); sync; if (!fork()) f(x); if (!fork()) g(y); // check;

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

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

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

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

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

2. spawn f(x) ? f(x) 1 spawn g(y) sync 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 % g++ myprog. cpp –lgrace –o myprog

“Moltes gràcies”

2. ? UNIVERSITY OF MASSACHUSETTS , AMHERST • Department of Computer Science

2. ? + UNIVERSITY OF MASSACHUSETTS , AMHERST • Department of Computer Science

2. ? + + UNIVERSITY OF MASSACHUSETTS , AMHERST • Department of Computer Science