Deadlock

• This shows a race condition and a deadlock.

• If A is locked by one thread and B by another, you have deadlock.

• If the same thread gets both locks, you get a race condition - i.e. different behavior depending on detailed interleaving of the thread.

• Avoid nesting different locks.

CALL OMP_INIT_LOCK (LCKA)

CALL OMP_INIT_LOCK (LCKB)

C$OMP PARALLEL SECTIONS

C$OMP SECTION

CALL OMP_SET_LOCK(LCKA)

CALL OMP_SET_LOCK(LCKB)

CALL USE_A_and_B (RES)

CALL OMP_UNSET_LOCK(LCKB)

CALL OMP_UNSET_LOCK(LCKA)

C$OMP SECTION

CALL OMP_SET_LOCK(LCKB)

CALL OMP_SET_LOCK(LCKA)

CALL USE_B_and_A (RES)

CALL OMP_UNSET_LOCK(LCKA)

CALL OMP_UNSET_LOCK(LCKB)

C$OMP END SECTIONS

Previous slide

Next slide

Back to first slide

View graphic version