diff options
Diffstat (limited to 'src/backend/storage/lmgr/proc.c')
| -rw-r--r-- | src/backend/storage/lmgr/proc.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/src/backend/storage/lmgr/proc.c b/src/backend/storage/lmgr/proc.c index f3e20038f42..162b1f919db 100644 --- a/src/backend/storage/lmgr/proc.c +++ b/src/backend/storage/lmgr/proc.c @@ -1043,10 +1043,19 @@ AuxiliaryPidGetProc(int pid) * Caller must have set MyProc->heldLocks to reflect locks already held * on the lockable object by this process (under all XIDs). * + * It's not actually guaranteed that we need to wait when this function is + * called, because it could be that when we try to find a position at which + * to insert ourself into the wait queue, we discover that we must be inserted + * ahead of everyone who wants a lock that conflict with ours. In that case, + * we get the lock immediately. Beause of this, it's sensible for this function + * to have a dontWait argument, despite the name. + * * The lock table's partition lock must be held at entry, and will be held * at exit. * - * Result: PROC_WAIT_STATUS_OK if we acquired the lock, PROC_WAIT_STATUS_ERROR if not (deadlock). + * Result: PROC_WAIT_STATUS_OK if we acquired the lock, PROC_WAIT_STATUS_ERROR + * if not (if dontWait = true, this is a deadlock; if dontWait = false, we + * would have had to wait). * * ASSUME: that no one will fiddle with the queue until after * we release the partition lock. @@ -1054,7 +1063,7 @@ AuxiliaryPidGetProc(int pid) * NOTES: The process queue is now a priority queue for locking. */ ProcWaitStatus -ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable) +ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable, bool dontWait) { LOCKMODE lockmode = locallock->tag.mode; LOCK *lock = locallock->lock; @@ -1168,6 +1177,13 @@ ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable) } /* + * At this point we know that we'd really need to sleep. If we've been + * commanded not to do that, bail out. + */ + if (dontWait) + return PROC_WAIT_STATUS_ERROR; + + /* * Insert self into queue, at the position determined above. */ if (insert_before) |