diff options
| author | Thomas Munro <tmunro@postgresql.org> | 2020-11-19 18:09:50 +1300 |
|---|---|---|
| committer | Thomas Munro <tmunro@postgresql.org> | 2020-11-19 18:13:46 +1300 |
| commit | 7888b0999488511e4266f2134053fa3a6505a155 (patch) | |
| tree | 4f22410c81fa8b08530d71d71fda71b199c93915 /src | |
| parent | 13b58f8934e6252868231c3493d49b8c2b363e5d (diff) | |
| download | postgresql-7888b0999488511e4266f2134053fa3a6505a155.tar.gz postgresql-7888b0999488511e4266f2134053fa3a6505a155.zip | |
Add BarrierArriveAndDetachExceptLast().
Provide a way for one process to continue the remaining phases of a
(previously) parallel computation alone. Later patches will use this to
extend Parallel Hash Join.
Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKG%2BA6ftXPz4oe92%2Bx8Er%2BxpGZqto70-Q_ERwRaSyA%3DafNg%40mail.gmail.com
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/storage/ipc/barrier.c | 22 | ||||
| -rw-r--r-- | src/include/storage/barrier.h | 1 |
2 files changed, 23 insertions, 0 deletions
diff --git a/src/backend/storage/ipc/barrier.c b/src/backend/storage/ipc/barrier.c index 3e200e02cc2..69afd586898 100644 --- a/src/backend/storage/ipc/barrier.c +++ b/src/backend/storage/ipc/barrier.c @@ -206,6 +206,28 @@ BarrierArriveAndDetach(Barrier *barrier) } /* + * Arrive at a barrier, and detach all but the last to arrive. Returns true if + * the caller was the last to arrive, and is therefore still attached. + */ +bool +BarrierArriveAndDetachExceptLast(Barrier *barrier) +{ + SpinLockAcquire(&barrier->mutex); + if (barrier->participants > 1) + { + --barrier->participants; + SpinLockRelease(&barrier->mutex); + + return false; + } + Assert(barrier->participants == 1); + ++barrier->phase; + SpinLockRelease(&barrier->mutex); + + return true; +} + +/* * Attach to a barrier. All waiting participants will now wait for this * participant to call BarrierArriveAndWait(), BarrierDetach() or * BarrierArriveAndDetach(). Return the current phase. diff --git a/src/include/storage/barrier.h b/src/include/storage/barrier.h index d71927cc2f7..e0de24378bf 100644 --- a/src/include/storage/barrier.h +++ b/src/include/storage/barrier.h @@ -37,6 +37,7 @@ typedef struct Barrier extern void BarrierInit(Barrier *barrier, int num_workers); extern bool BarrierArriveAndWait(Barrier *barrier, uint32 wait_event_info); extern bool BarrierArriveAndDetach(Barrier *barrier); +extern bool BarrierArriveAndDetachExceptLast(Barrier *barrier); extern int BarrierAttach(Barrier *barrier); extern bool BarrierDetach(Barrier *barrier); extern int BarrierPhase(Barrier *barrier); |