bool *satisfies_hot, bool *satisfies_key,
bool *satisfies_id,
HeapTuple oldtup, HeapTuple newtup);
+static bool heap_acquire_tuplock(Relation relation, ItemPointer tid,
+ LockTupleMode mode, LockWaitPolicy wait_policy,
+ bool *have_tuple_lock);
static void compute_new_xmax_infomask(TransactionId xmax, uint16 old_infomask,
uint16 old_infomask2, TransactionId add_to_xmax,
LockTupleMode mode, bool is_update,
uint16 *new_infomask2);
static TransactionId MultiXactIdGetUpdateXid(TransactionId xmax,
uint16 t_infomask);
+static bool DoesMultiXactIdConflict(MultiXactId multi, uint16 infomask,
+ LockTupleMode lockmode);
static void MultiXactIdWait(MultiXactId multi, MultiXactStatus status, uint16 infomask,
Relation rel, ItemPointer ctid, XLTW_Oper oper,
int *remaining);
* this arranges that we stay at the head of the line while rechecking
* tuple state.
*/
- if (!have_tuple_lock)
- {
- LockTupleTuplock(relation, &(tp.t_self), LockTupleExclusive);
- have_tuple_lock = true;
- }
+ heap_acquire_tuplock(relation, &(tp.t_self), LockTupleExclusive,
+ LockWaitBlock, &have_tuple_lock);
/*
* Sleep until concurrent transaction ends. Note that we don't care
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
- /*
- * Acquire tuple lock to establish our priority for the tuple (see
- * heap_lock_tuple). LockTuple will release us when we are
- * next-in-line for the tuple.
- *
- * If we are forced to "start over" below, we keep the tuple lock;
- * this arranges that we stay at the head of the line while rechecking
- * tuple state.
- */
- if (!have_tuple_lock)
- {
- LockTupleTuplock(relation, &(oldtup.t_self), *lockmode);
- have_tuple_lock = true;
- }
-
/*
* Now we have to do something about the existing locker. If it's a
* multi, sleep on it; we might be awakened before it is completely
* before actually going to sleep. If the update doesn't conflict
* with the locks, we just continue without sleeping (but making sure
* it is preserved).
+ *
+ * Before sleeping, we need to acquire tuple lock to establish our
+ * priority for the tuple (see heap_lock_tuple). LockTuple will
+ * release us when we are next-in-line for the tuple. Note we must not
+ * acquire the tuple lock until we're sure we're going to sleep;
+ * otherwise we're open for race conditions with other transactions
+ * holding the tuple lock which sleep on us.
+ *
+ * If we are forced to "start over" below, we keep the tuple lock;
+ * this arranges that we stay at the head of the line while rechecking
+ * tuple state.
*/
if (infomask & HEAP_XMAX_IS_MULTI)
{
TransactionId update_xact;
int remain;
+ /* acquire tuple lock, if necessary */
+ if (DoesMultiXactIdConflict((MultiXactId) xwait, infomask, *lockmode))
+ {
+ heap_acquire_tuplock(relation, &(oldtup.t_self), *lockmode,
+ LockWaitBlock, &have_tuple_lock);
+ }
+
/* wait for multixact */
MultiXactIdWait((MultiXactId) xwait, mxact_status, infomask,
relation, &oldtup.t_data->t_ctid, XLTW_Update,
}
else
{
- /* wait for regular transaction to end */
+ /*
+ * Wait for regular transaction to end; but first, acquire
+ * tuple lock.
+ */
+ heap_acquire_tuplock(relation, &(oldtup.t_self), *lockmode,
+ LockWaitBlock, &have_tuple_lock);
XactLockTableWait(xwait, relation, &oldtup.t_data->t_ctid,
XLTW_Update);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
return (MultiXactStatus) retval;
}
-
/*
* heap_lock_tuple - lock a tuple in shared or exclusive mode
*
pfree(members);
}
- /*
- * Acquire tuple lock to establish our priority for the tuple.
- * LockTuple will release us when we are next-in-line for the tuple.
- * We must do this even if we are share-locking.
- *
- * If we are forced to "start over" below, we keep the tuple lock;
- * this arranges that we stay at the head of the line while rechecking
- * tuple state.
- */
- if (!have_tuple_lock)
- {
- switch (wait_policy)
- {
- case LockWaitBlock:
- LockTupleTuplock(relation, tid, mode);
- break;
- case LockWaitSkip:
- if (!ConditionalLockTupleTuplock(relation, tid, mode))
- {
- result = HeapTupleWouldBlock;
- /* recovery code expects to have buffer lock held */
- LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
- goto failed;
- }
- break;
- case LockWaitError:
- if (!ConditionalLockTupleTuplock(relation, tid, mode))
- ereport(ERROR,
- (errcode(ERRCODE_LOCK_NOT_AVAILABLE),
- errmsg("could not obtain lock on row in relation \"%s\"",
- RelationGetRelationName(relation))));
- break;
- }
- have_tuple_lock = true;
- }
-
/*
* Initially assume that we will have to wait for the locking
* transaction(s) to finish. We check various cases below in which
{
/*
* If we're requesting NoKeyExclusive, we might also be able to
- * avoid sleeping; just ensure that there's no other lock type
- * than KeyShare. Note that this is a bit more involved than just
- * checking hint bits -- we need to expand the multixact to figure
- * out lock modes for each one (unless there was only one such
- * locker).
+ * avoid sleeping; just ensure that there no conflicting lock
+ * already acquired.
*/
if (infomask & HEAP_XMAX_IS_MULTI)
{
- int nmembers;
- MultiXactMember *members;
-
- /*
- * We don't need to allow old multixacts here; if that had
- * been the case, HeapTupleSatisfiesUpdate would have returned
- * MayBeUpdated and we wouldn't be here.
- */
- nmembers =
- GetMultiXactIdMembers(xwait, &members, false,
- HEAP_XMAX_IS_LOCKED_ONLY(infomask));
-
- if (nmembers <= 0)
+ if (!DoesMultiXactIdConflict((MultiXactId) xwait, infomask,
+ mode))
{
/*
- * No need to keep the previous xmax here. This is
- * unlikely to happen.
+ * No conflict, but if the xmax changed under us in the
+ * meantime, start over.
*/
- require_sleep = false;
- }
- else
- {
- int i;
- bool allowed = true;
-
- for (i = 0; i < nmembers; i++)
- {
- if (members[i].status != MultiXactStatusForKeyShare)
- {
- allowed = false;
- break;
- }
- }
- if (allowed)
- {
- /*
- * if the xmax changed under us in the meantime, start
- * over.
- */
- LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
- if (xmax_infomask_changed(tuple->t_data->t_infomask, infomask) ||
- !TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple->t_data),
- xwait))
- {
- pfree(members);
- goto l3;
- }
- /* otherwise, we're good */
- require_sleep = false;
- }
+ LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+ if (xmax_infomask_changed(tuple->t_data->t_infomask, infomask) ||
+ !TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple->t_data),
+ xwait))
+ goto l3;
- pfree(members);
+ /* otherwise, we're good */
+ require_sleep = false;
}
}
else if (HEAP_XMAX_IS_KEYSHR_LOCKED(infomask))
if (require_sleep)
{
+ /*
+ * Acquire tuple lock to establish our priority for the tuple.
+ * LockTuple will release us when we are next-in-line for the tuple.
+ * We must do this even if we are share-locking.
+ *
+ * If we are forced to "start over" below, we keep the tuple lock;
+ * this arranges that we stay at the head of the line while rechecking
+ * tuple state.
+ */
+ if (!heap_acquire_tuplock(relation, tid, mode, wait_policy,
+ &have_tuple_lock))
+ {
+ /*
+ * This can only happen if wait_policy is Skip and the lock
+ * couldn't be obtained.
+ */
+ result = HeapTupleWouldBlock;
+ /* recovery code expects to have buffer lock held */
+ LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
+ goto failed;
+ }
+
if (infomask & HEAP_XMAX_IS_MULTI)
{
MultiXactStatus status = get_mxact_status_for_lock(mode, false);
return HeapTupleMayBeUpdated;
}
+/*
+ * Acquire heavyweight lock on the given tuple, in preparation for acquiring
+ * its normal, Xmax-based tuple lock.
+ *
+ * have_tuple_lock is an input and output parameter: on input, it indicates
+ * whether the lock has previously been acquired (and this function does
+ * nothing in that case). If this function returns success, have_tuple_lock
+ * has been flipped to true.
+ *
+ * Returns false if it was unable to obtain the lock; this can only happen if
+ * wait_policy is Skip.
+ */
+static bool
+heap_acquire_tuplock(Relation relation, ItemPointer tid, LockTupleMode mode,
+ LockWaitPolicy wait_policy, bool *have_tuple_lock)
+{
+ if (*have_tuple_lock)
+ return true;
+
+ switch (wait_policy)
+ {
+ case LockWaitBlock:
+ LockTupleTuplock(relation, tid, mode);
+ break;
+
+ case LockWaitSkip:
+ if (!ConditionalLockTupleTuplock(relation, tid, mode))
+ return false;
+ break;
+
+ case LockWaitError:
+ if (!ConditionalLockTupleTuplock(relation, tid, mode))
+ ereport(ERROR,
+ (errcode(ERRCODE_LOCK_NOT_AVAILABLE),
+ errmsg("could not obtain lock on row in relation \"%s\"",
+ RelationGetRelationName(relation))));
+ break;
+ }
+ *have_tuple_lock = true;
+
+ return true;
+}
/*
* Given an original set of Xmax and infomask, and a transaction (identified by
tuple->t_infomask);
}
+/*
+ * Does the given multixact conflict with the current transaction grabbing a
+ * tuple lock of the given strength?
+ *
+ * The passed infomask pairs up with the given multixact in the tuple header.
+ */
+static bool
+DoesMultiXactIdConflict(MultiXactId multi, uint16 infomask,
+ LockTupleMode lockmode)
+{
+ bool allow_old;
+ int nmembers;
+ MultiXactMember *members;
+ bool result = false;
+
+ allow_old = !(infomask & HEAP_LOCK_MASK) && HEAP_XMAX_IS_LOCKED_ONLY(infomask);
+ nmembers = GetMultiXactIdMembers(multi, &members, allow_old,
+ HEAP_XMAX_IS_LOCKED_ONLY(infomask));
+ if (nmembers >= 0)
+ {
+ int i;
+
+ for (i = 0; i < nmembers; i++)
+ {
+ TransactionId memxid;
+ LockTupleMode memlockmode;
+
+ memlockmode = LOCKMODE_from_mxstatus(members[i].status);
+ /* ignore members that don't conflict with the lock we want */
+ if (!DoLockModesConflict(memlockmode, lockmode))
+ continue;
+
+ /* ignore members from current xact */
+ memxid = members[i].xid;
+ if (TransactionIdIsCurrentTransactionId(memxid))
+ continue;
+
+ if (ISUPDATE_from_mxstatus(members[i].status))
+ {
+ /* ignore aborted updaters */
+ if (TransactionIdDidAbort(memxid))
+ continue;
+ }
+ else
+ {
+ /* ignore lockers-only that are no longer in progress */
+ if (!TransactionIdIsInProgress(memxid))
+ continue;
+ }
+
+ /*
+ * Whatever remains are either live lockers that conflict with our
+ * wanted lock, and updaters that are not aborted. Those conflict
+ * with what we want, so return true.
+ */
+ result = true;
+ break;
+ }
+ pfree(members);
+ }
+
+ return result;
+}
+
/*
* Do_MultiXactIdWait
* Actual implementation for the two functions below.
projects / postgresql / commitdiff