UNIVERSITY OF MASSACHUSETTS , AMHERST • Department of Computer ScienceUNIVERSITY OF MASSACHUSETTS, AMHERST • Department of Computer Science

Grace: Safe Multithreaded Programming for C/C++

Emery BergerUniversity of Massachusetts, UPC/BSC

www.cs.umass.edu/~emery

UNIVERSITY OF MASSACHUSETTS , AMHERST • Department 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

UNIVERSITY OF MASSACHUSETTS , AMHERST • Department 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

UNIVERSITY OF MASSACHUSETTS , AMHERST • Department of Computer Science

“ ”

race condition

atomicity violation

deadlock

order violation

sequential

sequential

race conditions

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

Grace

% g++ myprog.cpp –lpthread –o myprog

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% g++ myprog.cpp –lgrace –o myprog

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% g++ myprog.cpp –lgrace –o myprog

sequential

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% g++ myprog.cpp –lgrace –o myprog

sequentialrace conditions

atomicity violations

deadlock

order violations

Grace

% g++ myprog.cpp –lgrace –o myprog

sequentialrace conditions

atomicity violations

deadlock

order violations

Safe and (usually) fast…

benign race

Grace

sequential + ?1.

Grace

sequential + ?1.

2.

Grace

sequential + ?1.

2.

3.

sequential + ?1.

sequential + ?1.

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

sequential + ?1.

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

spawnf(x)

sequential + ?1.

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

f(x)

spawnf(x)

sequential + ?1.

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

f(x)

spawnf(x)

spawng(y)

sequential + ?1.

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

f(x)g(y)

spawnf(x)

spawng(y)

sequential + ?1.

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

f(x)g(y)

spawnf(x)

spawng(y)

sync

sequential + ?1.

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

f(x)g(y)

spawnf(x)

spawng(y)

sync

sequential + ?1.

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

f(x)g(y)

spawnf(x)

spawng(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.

+

?2.

?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)

spawnf(x)

spawng(y)

sync

?2.

if (!fork()) f(x);if (!fork()) g(y);// check;

f(x)g(y)

spawnf(x)

spawng(y)

sync

?2.

if (!fork()) f(x);if (!fork()) g(y);// check;

f(x)g(y)

spawnf(x)

spawng(y)

sync

Note:Nested threads ok

?2.f(x)

g(y)

spawnf(x)

spawng(y)

syncmmap

?2.f(x)

g(y)

spawnf(x)

spawng(y)

syncmmap

?2.f(x)

g(y)

spawnf(x)

spawng(y)

syncmmap

?2.f(x)

g(y)

spawnf(x)

spawng(y)

sync

?2.f(x)

g(y)

spawnf(x)

spawng(y)

sync

1

?2.f(x)

g(y)

spawnf(x)

spawng(y)

sync

12

?2.

scalable heap+ aligned globals

I/O (buffering + ordering)

3.

More detailed results…

Grace

sequentialrace conditions

atomicity violations

deadlock

order violations

Grace

sequentialrace conditions

atomicity violations

deadlock

order violations

Grace

sequentialrace conditions

atomicity violations

deadlock

order violations

Grace

sequentialrace conditions

atomicity violations

deadlock

order violations

% g++ myprog.cpp –lgrace –o myprog

“Moltes gràcies”

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

?2.

+

UNIVERSITY OF MASSACHUSETTS , AMHERST • Department of Computer Science

?2.

+ +