diff options
| -rw-r--r-- | src/backend/storage/ipc/procarray.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c index 51f8099cad2..60b7a5db8e0 100644 --- a/src/backend/storage/ipc/procarray.c +++ b/src/backend/storage/ipc/procarray.c @@ -840,13 +840,20 @@ ProcArrayClearTransaction(PGPROC *proc) size_t pgxactoff; /* - * We can skip locking ProcArrayLock exclusively here, because this action - * does not actually change anyone's view of the set of running XIDs: our - * entry is duplicate with the gxact that has already been inserted into - * the ProcArray. But need it in shared mode for pgproc->pgxactoff to stay - * the same. + * Currently we need to lock ProcArrayLock exclusively here, as we + * increment xactCompletionCount below. We also need it at least in shared + * mode for pgproc->pgxactoff to stay the same below. + * + * We could however, as this action does not actually change anyone's view + * of the set of running XIDs (our entry is duplicate with the gxact that + * has already been inserted into the ProcArray), lower the lock level to + * shared if we were to make xactCompletionCount an atomic variable. But + * that doesn't seem worth it currently, as a 2PC commit is heavyweight + * enough for this not to be the bottleneck. If it ever becomes a + * bottleneck it may also be worth considering to combine this with the + * subsequent ProcArrayRemove() */ - LWLockAcquire(ProcArrayLock, LW_SHARED); + LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); pgxactoff = proc->pgxactoff; |