-$Header: /cvsroot/pgsql/src/backend/storage/lmgr/README,v 1.10 2002/04/15 23:46:13 momjian Exp $
+$Header: /cvsroot/pgsql/src/backend/storage/lmgr/README,v 1.11 2002/07/19 00:17:40 momjian Exp $
LOCKING OVERVIEW
* Spinlocks. These are intended for *very* short-term locks. If a lock
is to be held more than a few dozen instructions, or across any sort of
-kernel call (or even a call to a nontrivial subroutine), don't use a spinlock.
-Spinlocks are primarily used as infrastructure for lightweight locks.
-They are implemented using a hardware atomic-test-and-set instruction,
-if available. Waiting processes busy-loop until they can get the lock.
-There is no provision for deadlock detection, automatic release on error,
-or any other nicety. There is a timeout if the lock cannot be gotten after
-a minute or so (which is approximately forever in comparison to the intended
-lock hold time, so this is certainly an error condition).
-
-* Lightweight locks (LWLocks). These locks are typically used to interlock
-access to datastructures in shared memory. LWLocks support both exclusive
-and shared lock modes (for read/write and read-only access to a shared object).
-There is no provision for deadlock detection, but the LWLock manager will
-automatically release held LWLocks during elog() recovery, so it is safe to
-raise an error while holding LWLocks. Obtaining or releasing an LWLock is
-quite fast (a few dozen instructions) when there is no contention for the
-lock. When a process has to wait for an LWLock, it blocks on a SysV semaphore
-so as to not consume CPU time. Waiting processes will be granted the lock
-in arrival order. There is no timeout.
-
-* Regular locks (a/k/a heavyweight locks). The regular lock manager supports
-a variety of lock modes with table-driven semantics, and it has full deadlock
-detection and automatic release at transaction end. Regular locks should be
-used for all user-driven lock requests.
-
-Acquisition of either a spinlock or a lightweight lock causes query cancel
-and die() interrupts to be held off until all such locks are released.
-No such restriction exists for regular locks, however. Also note that we
-can accept query cancel and die() interrupts while waiting for a regular
-lock, but we will not accept them while waiting for spinlocks or LW locks.
-It is therefore not a good idea to use LW locks when the wait time might
-exceed a few seconds.
+kernel call (or even a call to a nontrivial subroutine), don't use a
+spinlock. Spinlocks are primarily used as infrastructure for lightweight
+locks. They are implemented using a hardware atomic-test-and-set
+instruction, if available. Waiting processes busy-loop until they can
+get the lock. There is no provision for deadlock detection, automatic
+release on error, or any other nicety. There is a timeout if the lock
+cannot be gotten after a minute or so (which is approximately forever in
+comparison to the intended lock hold time, so this is certainly an error
+condition).
+
+* Lightweight locks (LWLocks). These locks are typically used to
+interlock access to datastructures in shared memory. LWLocks support
+both exclusive and shared lock modes (for read/write and read-only
+access to a shared object). There is no provision for deadlock
+detection, but the LWLock manager will automatically release held
+LWLocks during elog() recovery, so it is safe to raise an error while
+holding LWLocks. Obtaining or releasing an LWLock is quite fast (a few
+dozen instructions) when there is no contention for the lock. When a
+process has to wait for an LWLock, it blocks on a SysV semaphore so as
+to not consume CPU time. Waiting processes will be granted the lock in
+arrival order. There is no timeout.
+
+* Regular locks (a/k/a heavyweight locks). The regular lock manager
+supports a variety of lock modes with table-driven semantics, and it has
+full deadlock detection and automatic release at transaction end.
+Regular locks should be used for all user-driven lock requests.
+
+Acquisition of either a spinlock or a lightweight lock causes query
+cancel and die() interrupts to be held off until all such locks are
+released. No such restriction exists for regular locks, however. Also
+note that we can accept query cancel and die() interrupts while waiting
+for a regular lock, but we will not accept them while waiting for
+spinlocks or LW locks. It is therefore not a good idea to use LW locks
+when the wait time might exceed a few seconds.
The rest of this README file discusses the regular lock manager in detail.
LOCK DATA STRUCTURES
There are two fundamental lock structures: the per-lockable-object LOCK
-struct, and the per-lock-holder HOLDER struct. A LOCK object exists
+struct, and the per-lock-holder PROCLOCK struct. A LOCK object exists
for each lockable object that currently has locks held or requested on it.
-A HOLDER struct exists for each transaction that is holding or requesting
+A PROCLOCK struct exists for each transaction that is holding or requesting
lock(s) on each LOCK object.
Lock methods describe the overall locking behavior. Currently there are
is 1 if and only if requested[i] > granted[i].
lockHolders -
- This is a shared memory queue of all the HOLDER structs associated with
- the lock object. Note that both granted and waiting HOLDERs are in this
- list (indeed, the same HOLDER might have some already-granted locks and
+ This is a shared memory queue of all the PROCLOCK structs associated with
+ the lock object. Note that both granted and waiting PROCLOCKs are in this
+ list (indeed, the same PROCLOCK might have some already-granted locks and
be waiting for more!).
waitProcs -
---------------------------------------------------------------------------
-The lock manager's HOLDER objects contain:
+The lock manager's PROCLOCK objects contain:
tag -
The key fields that are used for hashing entries in the shared memory
- holder hash table. This is declared as a separate struct to ensure that
+ PROCLOCK hash table. This is declared as a separate struct to ensure that
we always zero out the correct number of bytes.
tag.lock
- SHMEM offset of the LOCK object this holder is for.
+ SHMEM offset of the LOCK object this PROCLOCK is for.
tag.proc
- SHMEM offset of PROC of backend process that owns this holder.
+ SHMEM offset of PROC of backend process that owns this PROCLOCK.
tag.xid
- XID of transaction this holder is for, or InvalidTransactionId
- if the holder is for session-level locking.
+ XID of transaction this PROCLOCK is for, or InvalidTransactionId
+ if the PROCLOCK is for session-level locking.
Note that this structure will support multiple transactions running
concurrently in one backend, which may be handy if we someday decide
transaction operations like VACUUM.
holding -
- The number of successfully acquired locks of each type for this holder.
+ The number of successfully acquired locks of each type for this PROCLOCK.
This should be <= the corresponding granted[] value of the lock object!
nHolding -
Sum of the holding[] array.
lockLink -
- List link for shared memory queue of all the HOLDER objects for the
+ List link for shared memory queue of all the PROCLOCK objects for the
same LOCK.
procLink -
- List link for shared memory queue of all the HOLDER objects for the
+ List link for shared memory queue of all the PROCLOCK objects for the
same backend.
---------------------------------------------------------------------------
needed to deal with Postgres' generalized locking model.
A key design consideration is that we want to make routine operations
-(lock grant and release) run quickly when there is no deadlock, and avoid
-the overhead of deadlock handling as much as possible. We do this using
-an "optimistic waiting" approach: if a process cannot acquire the lock
-it wants immediately, it goes to sleep without any deadlock check. But
-it also sets a delay timer, with a delay of DeadlockTimeout milliseconds
-(typically set to one second). If the delay expires before the process is
-granted the lock it wants, it runs the deadlock detection/breaking code.
-Normally this code will determine that there is no deadlock condition,
-and then the process will go back to sleep and wait quietly until it is
-granted the lock. But if a deadlock condition does exist, it will be
-resolved, usually by aborting the detecting process' transaction. In this
-way, we avoid deadlock handling overhead whenever the wait time for a lock
-is less than DeadlockTimeout, while not imposing an unreasonable delay of
-detection when there is an error.
+(lock grant and release) run quickly when there is no deadlock, and
+avoid the overhead of deadlock handling as much as possible. We do this
+using an "optimistic waiting" approach: if a process cannot acquire the
+lock it wants immediately, it goes to sleep without any deadlock check.
+But it also sets a delay timer, with a delay of DeadlockTimeout
+milliseconds (typically set to one second). If the delay expires before
+the process is granted the lock it wants, it runs the deadlock
+detection/breaking code. Normally this code will determine that there is
+no deadlock condition, and then the process will go back to sleep and
+wait quietly until it is granted the lock. But if a deadlock condition
+does exist, it will be resolved, usually by aborting the detecting
+process' transaction. In this way, we avoid deadlock handling overhead
+whenever the wait time for a lock is less than DeadlockTimeout, while
+not imposing an unreasonable delay of detection when there is an error.
Lock acquisition (routines LockAcquire and ProcSleep) follows these rules:
-1. A lock request is granted immediately if it does not conflict with any
-existing or waiting lock request, or if the process already holds an
+1. A lock request is granted immediately if it does not conflict with
+any existing or waiting lock request, or if the process already holds an
instance of the same lock type (eg, there's no penalty to acquire a read
-lock twice). Note that a process never conflicts with itself, eg one can
-obtain read lock when one already holds exclusive lock.
-
-2. Otherwise the process joins the lock's wait queue. Normally it will be
-added to the end of the queue, but there is an exception: if the process
-already holds locks on this same lockable object that conflict with the
-request of any pending waiter, then the process will be inserted in the
-wait queue just ahead of the first such waiter. (If we did not make this
-check, the deadlock detection code would adjust the queue order to resolve
-the conflict, but it's relatively cheap to make the check in ProcSleep and
-avoid a deadlock timeout delay in this case.) Note special case when
-inserting before the end of the queue: if the process's request does not
-conflict with any existing lock nor any waiting request before its insertion
-point, then go ahead and grant the lock without waiting.
+lock twice). Note that a process never conflicts with itself, eg one
+can obtain read lock when one already holds exclusive lock.
+
+2. Otherwise the process joins the lock's wait queue. Normally it will
+be added to the end of the queue, but there is an exception: if the
+process already holds locks on this same lockable object that conflict
+with the request of any pending waiter, then the process will be
+inserted in the wait queue just ahead of the first such waiter. (If we
+did not make this check, the deadlock detection code would adjust the
+queue order to resolve the conflict, but it's relatively cheap to make
+the check in ProcSleep and avoid a deadlock timeout delay in this case.)
+ Note special case when inserting before the end of the queue: if the
+process's request does not conflict with any existing lock nor any
+waiting request before its insertion point, then go ahead and grant the
+lock without waiting.
When a lock is released, the lock release routine (ProcLockWakeup) scans
the lock object's wait queue. Each waiter is awoken if (a) its request
does not conflict with already-granted locks, and (b) its request does
not conflict with the requests of prior un-wakable waiters. Rule (b)
-ensures that conflicting requests are granted in order of arrival.
-There are cases where a later waiter must be allowed to go in front of
+ensures that conflicting requests are granted in order of arrival. There
+are cases where a later waiter must be allowed to go in front of
conflicting earlier waiters to avoid deadlock, but it is not
ProcLockWakeup's responsibility to recognize these cases; instead, the
deadlock detection code will re-order the wait queue when necessary.
various processes as nodes in a directed graph (the waits-for graph or
WFG). There is a graph edge leading from process A to process B if A
waits for B, ie, A is waiting for some lock and B holds a conflicting
-lock. There is a deadlock condition if and only if the WFG contains
-a cycle. We detect cycles by searching outward along waits-for edges
-to see if we return to our starting point. There are three possible
+lock. There is a deadlock condition if and only if the WFG contains a
+cycle. We detect cycles by searching outward along waits-for edges to
+see if we return to our starting point. There are three possible
outcomes:
1. All outgoing paths terminate at a running process (which has no
outgoing edge).
-2. A deadlock is detected by looping back to the start point. We resolve
-such a deadlock by canceling the start point's lock request and reporting
-an error in that transaction, which normally leads to transaction abort
-and release of that transaction's held locks. Note that it's sufficient
-to cancel one request to remove the cycle; we don't need to kill all the
-transactions involved.
+2. A deadlock is detected by looping back to the start point. We
+resolve such a deadlock by canceling the start point's lock request and
+reporting an error in that transaction, which normally leads to
+transaction abort and release of that transaction's held locks. Note
+that it's sufficient to cancel one request to remove the cycle; we don't
+need to kill all the transactions involved.
3. Some path(s) loop back to a node other than the start point. This
-indicates a deadlock, but one that does not involve our starting process.
-We ignore this condition on the grounds that resolving such a deadlock
-is the responsibility of the processes involved --- killing our start-
-point process would not resolve the deadlock. So, cases 1 and 3 both
-report "no deadlock".
+indicates a deadlock, but one that does not involve our starting
+process. We ignore this condition on the grounds that resolving such a
+deadlock is the responsibility of the processes involved --- killing our
+start- point process would not resolve the deadlock. So, cases 1 and 3
+both report "no deadlock".
Postgres' situation is a little more complex than the standard discussion
of deadlock detection, for two reasons:
1. A process can be waiting for more than one other process, since there
-might be multiple holders of (non-conflicting) lock types that all conflict
-with the waiter's request. This creates no real difficulty however; we
-simply need to be prepared to trace more than one outgoing edge.
+might be multiple PROCLOCKs of (non-conflicting) lock types that all
+conflict with the waiter's request. This creates no real difficulty
+however; we simply need to be prepared to trace more than one outgoing
+edge.
2. If a process A is behind a process B in some lock's wait queue, and
their requested locks conflict, then we must say that A waits for B, since
ProcLockWakeup, in case the canceled waiter was soft-blocking other
waiters.
-4. We can minimize excess rearrangement-trial work by being careful to scan
-the wait queue from the front when looking for soft edges. For example,
-if we have queue order A,B,C and C has deadlock conflicts with both A and B,
-we want to generate the "C before A" constraint first, rather than wasting
-time with "C before B", which won't move C far enough up. So we look for
-soft edges outgoing from C starting at the front of the wait queue.
+4. We can minimize excess rearrangement-trial work by being careful to
+scan the wait queue from the front when looking for soft edges. For
+example, if we have queue order A,B,C and C has deadlock conflicts with
+both A and B, we want to generate the "C before A" constraint first,
+rather than wasting time with "C before B", which won't move C far
+enough up. So we look for soft edges outgoing from C starting at the
+front of the wait queue.
5. The working data structures needed by the deadlock detection code can
be limited to numbers of entries computed from MaxBackends. Therefore,
-we can allocate the worst-case space needed during backend startup.
-This seems a safer approach than trying to allocate workspace on the fly;
-we don't want to risk having the deadlock detector run out of memory,
-else we really have no guarantees at all that deadlock will be detected.
+we can allocate the worst-case space needed during backend startup. This
+seems a safer approach than trying to allocate workspace on the fly; we
+don't want to risk having the deadlock detector run out of memory, else
+we really have no guarantees at all that deadlock will be detected.
+
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/deadlock.c,v 1.11 2002/07/18 23:06:19 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/deadlock.c,v 1.12 2002/07/19 00:17:40 momjian Exp $
*
* Interface:
*
{
PGPROC *proc;
LOCK *lock;
- HOLDER *holder;
+ PROCLOCK *holder;
SHM_QUEUE *lockHolders;
LOCKMETHODTABLE *lockMethodTable;
PROC_QUEUE *waitQueue;
*/
lockHolders = &(lock->lockHolders);
- holder = (HOLDER *) SHMQueueNext(lockHolders, lockHolders,
- offsetof(HOLDER, lockLink));
+ holder = (PROCLOCK *) SHMQueueNext(lockHolders, lockHolders,
+ offsetof(PROCLOCK, lockLink));
while (holder)
{
}
}
- holder = (HOLDER *) SHMQueueNext(lockHolders, &holder->lockLink,
- offsetof(HOLDER, lockLink));
+ holder = (PROCLOCK *) SHMQueueNext(lockHolders, &holder->lockLink,
+ offsetof(PROCLOCK, lockLink));
}
/*
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lock.c,v 1.109 2002/07/18 23:06:19 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/lock.c,v 1.110 2002/07/19 00:17:40 momjian Exp $
*
* NOTES
* Outside modules can create a lock table and acquire/release
static int WaitOnLock(LOCKMETHOD lockmethod, LOCKMODE lockmode,
- LOCK *lock, HOLDER *holder);
+ LOCK *lock, PROCLOCK *holder);
static void LockCountMyLocks(SHMEM_OFFSET lockOffset, PGPROC *proc,
int *myHolding);
inline static void
-HOLDER_PRINT(const char *where, const HOLDER *holderP)
+PROCLOCK_PRINT(const char *where, const PROCLOCK *holderP)
{
if (
- (((HOLDER_LOCKMETHOD(*holderP) == DEFAULT_LOCKMETHOD && Trace_locks)
- || (HOLDER_LOCKMETHOD(*holderP) == USER_LOCKMETHOD && Trace_userlocks))
+ (((PROCLOCK_LOCKMETHOD(*holderP) == DEFAULT_LOCKMETHOD && Trace_locks)
+ || (PROCLOCK_LOCKMETHOD(*holderP) == USER_LOCKMETHOD && Trace_userlocks))
&& (((LOCK *) MAKE_PTR(holderP->tag.lock))->tag.relId >= (Oid) Trace_lock_oidmin))
|| (Trace_lock_table && (((LOCK *) MAKE_PTR(holderP->tag.lock))->tag.relId == Trace_lock_table))
)
elog(LOG,
"%s: holder(%lx) lock(%lx) tbl(%d) proc(%lx) xid(%u) hold(%d,%d,%d,%d,%d,%d,%d)=%d",
where, MAKE_OFFSET(holderP), holderP->tag.lock,
- HOLDER_LOCKMETHOD(*(holderP)),
+ PROCLOCK_LOCKMETHOD(*(holderP)),
holderP->tag.proc, holderP->tag.xid,
holderP->holding[1], holderP->holding[2], holderP->holding[3],
holderP->holding[4], holderP->holding[5], holderP->holding[6],
#else /* not LOCK_DEBUG */
#define LOCK_PRINT(where, lock, type)
-#define HOLDER_PRINT(where, holderP)
+#define PROCLOCK_PRINT(where, holderP)
#endif /* not LOCK_DEBUG */
Assert(lockMethodTable->lockHash->hash == tag_hash);
/*
- * allocate a hash table for HOLDER structs. This is used to store
+ * allocate a hash table for PROCLOCK structs. This is used to store
* per-lock-holder information.
*/
- info.keysize = sizeof(HOLDERTAG);
- info.entrysize = sizeof(HOLDER);
+ info.keysize = sizeof(PROCLOCKTAG);
+ info.entrysize = sizeof(PROCLOCK);
info.hash = tag_hash;
hash_flags = (HASH_ELEM | HASH_FUNCTION);
LockAcquire(LOCKMETHOD lockmethod, LOCKTAG *locktag,
TransactionId xid, LOCKMODE lockmode, bool dontWait)
{
- HOLDER *holder;
- HOLDERTAG holdertag;
+ PROCLOCK *holder;
+ PROCLOCKTAG holdertag;
HTAB *holderTable;
bool found;
LOCK *lock;
/*
* Create the hash key for the holder table.
*/
- MemSet(&holdertag, 0, sizeof(HOLDERTAG)); /* must clear padding,
+ MemSet(&holdertag, 0, sizeof(PROCLOCKTAG)); /* must clear padding,
* needed */
holdertag.lock = MAKE_OFFSET(lock);
holdertag.proc = MAKE_OFFSET(MyProc);
* Find or create a holder entry with this tag
*/
holderTable = lockMethodTable->holderHash;
- holder = (HOLDER *) hash_search(holderTable,
+ holder = (PROCLOCK *) hash_search(holderTable,
(void *) &holdertag,
HASH_ENTER, &found);
if (!holder)
/* Add holder to appropriate lists */
SHMQueueInsertBefore(&lock->lockHolders, &holder->lockLink);
SHMQueueInsertBefore(&MyProc->procHolders, &holder->procLink);
- HOLDER_PRINT("LockAcquire: new", holder);
+ PROCLOCK_PRINT("LockAcquire: new", holder);
}
else
{
- HOLDER_PRINT("LockAcquire: found", holder);
+ PROCLOCK_PRINT("LockAcquire: found", holder);
Assert((holder->nHolding >= 0) && (holder->holding[lockmode] >= 0));
Assert(holder->nHolding <= lock->nGranted);
if (holder->holding[lockmode] > 0)
{
GrantLock(lock, holder, lockmode);
- HOLDER_PRINT("LockAcquire: owning", holder);
+ PROCLOCK_PRINT("LockAcquire: owning", holder);
LWLockRelease(masterLock);
return TRUE;
}
if (myHolding[lockmode] > 0)
{
GrantLock(lock, holder, lockmode);
- HOLDER_PRINT("LockAcquire: my other XID owning", holder);
+ PROCLOCK_PRINT("LockAcquire: my other XID owning", holder);
LWLockRelease(masterLock);
return TRUE;
}
{
SHMQueueDelete(&holder->lockLink);
SHMQueueDelete(&holder->procLink);
- holder = (HOLDER *) hash_search(holderTable,
+ holder = (PROCLOCK *) hash_search(holderTable,
(void *) holder,
HASH_REMOVE, NULL);
if (!holder)
elog(WARNING, "LockAcquire: remove holder, table corrupted");
}
else
- HOLDER_PRINT("LockAcquire: NHOLDING", holder);
+ PROCLOCK_PRINT("LockAcquire: NHOLDING", holder);
lock->nRequested--;
lock->requested[lockmode]--;
LOCK_PRINT("LockAcquire: conditional lock failed", lock, lockmode);
*/
if (!((holder->nHolding > 0) && (holder->holding[lockmode] > 0)))
{
- HOLDER_PRINT("LockAcquire: INCONSISTENT", holder);
+ PROCLOCK_PRINT("LockAcquire: INCONSISTENT", holder);
LOCK_PRINT("LockAcquire: INCONSISTENT", lock, lockmode);
/* Should we retry ? */
LWLockRelease(masterLock);
return FALSE;
}
- HOLDER_PRINT("LockAcquire: granted", holder);
+ PROCLOCK_PRINT("LockAcquire: granted", holder);
LOCK_PRINT("LockAcquire: granted", lock, lockmode);
}
LockCheckConflicts(LOCKMETHODTABLE *lockMethodTable,
LOCKMODE lockmode,
LOCK *lock,
- HOLDER *holder,
+ PROCLOCK *holder,
PGPROC *proc,
int *myHolding) /* myHolding[] array or NULL */
{
*/
if (!(lockMethodTable->conflictTab[lockmode] & lock->grantMask))
{
- HOLDER_PRINT("LockCheckConflicts: no conflict", holder);
+ PROCLOCK_PRINT("LockCheckConflicts: no conflict", holder);
return STATUS_OK;
}
if (!(lockMethodTable->conflictTab[lockmode] & bitmask))
{
/* no conflict. OK to get the lock */
- HOLDER_PRINT("LockCheckConflicts: resolved", holder);
+ PROCLOCK_PRINT("LockCheckConflicts: resolved", holder);
return STATUS_OK;
}
- HOLDER_PRINT("LockCheckConflicts: conflicting", holder);
+ PROCLOCK_PRINT("LockCheckConflicts: conflicting", holder);
return STATUS_FOUND;
}
LockCountMyLocks(SHMEM_OFFSET lockOffset, PGPROC *proc, int *myHolding)
{
SHM_QUEUE *procHolders = &(proc->procHolders);
- HOLDER *holder;
+ PROCLOCK *holder;
int i;
MemSet(myHolding, 0, MAX_LOCKMODES * sizeof(int));
- holder = (HOLDER *) SHMQueueNext(procHolders, procHolders,
- offsetof(HOLDER, procLink));
+ holder = (PROCLOCK *) SHMQueueNext(procHolders, procHolders,
+ offsetof(PROCLOCK, procLink));
while (holder)
{
myHolding[i] += holder->holding[i];
}
- holder = (HOLDER *) SHMQueueNext(procHolders, &holder->procLink,
- offsetof(HOLDER, procLink));
+ holder = (PROCLOCK *) SHMQueueNext(procHolders, &holder->procLink,
+ offsetof(PROCLOCK, procLink));
}
}
* and have its waitLock/waitHolder fields cleared. That's not done here.
*/
void
-GrantLock(LOCK *lock, HOLDER *holder, LOCKMODE lockmode)
+GrantLock(LOCK *lock, PROCLOCK *holder, LOCKMODE lockmode)
{
lock->nGranted++;
lock->granted[lockmode]++;
*/
static int
WaitOnLock(LOCKMETHOD lockmethod, LOCKMODE lockmode,
- LOCK *lock, HOLDER *holder)
+ LOCK *lock, PROCLOCK *holder)
{
LOCKMETHODTABLE *lockMethodTable = LockMethodTable[lockmethod];
char *new_status,
LOCK *lock;
LWLockId masterLock;
LOCKMETHODTABLE *lockMethodTable;
- HOLDER *holder;
- HOLDERTAG holdertag;
+ PROCLOCK *holder;
+ PROCLOCKTAG holdertag;
HTAB *holderTable;
bool wakeupNeeded = false;
/*
* Find the holder entry for this holder.
*/
- MemSet(&holdertag, 0, sizeof(HOLDERTAG)); /* must clear padding,
+ MemSet(&holdertag, 0, sizeof(PROCLOCKTAG)); /* must clear padding,
* needed */
holdertag.lock = MAKE_OFFSET(lock);
holdertag.proc = MAKE_OFFSET(MyProc);
TransactionIdStore(xid, &holdertag.xid);
holderTable = lockMethodTable->holderHash;
- holder = (HOLDER *) hash_search(holderTable,
+ holder = (PROCLOCK *) hash_search(holderTable,
(void *) &holdertag,
HASH_FIND_SAVE, NULL);
if (!holder)
elog(WARNING, "LockRelease: holder table corrupted");
return FALSE;
}
- HOLDER_PRINT("LockRelease: found", holder);
+ PROCLOCK_PRINT("LockRelease: found", holder);
/*
* Check that we are actually holding a lock of the type we want to
*/
if (!(holder->holding[lockmode] > 0))
{
- HOLDER_PRINT("LockRelease: WRONGTYPE", holder);
+ PROCLOCK_PRINT("LockRelease: WRONGTYPE", holder);
Assert(holder->holding[lockmode] >= 0);
LWLockRelease(masterLock);
elog(WARNING, "LockRelease: you don't own a lock of type %s",
*/
holder->holding[lockmode]--;
holder->nHolding--;
- HOLDER_PRINT("LockRelease: updated", holder);
+ PROCLOCK_PRINT("LockRelease: updated", holder);
Assert((holder->nHolding >= 0) && (holder->holding[lockmode] >= 0));
/*
*/
if (holder->nHolding == 0)
{
- HOLDER_PRINT("LockRelease: deleting", holder);
+ PROCLOCK_PRINT("LockRelease: deleting", holder);
SHMQueueDelete(&holder->lockLink);
SHMQueueDelete(&holder->procLink);
- holder = (HOLDER *) hash_search(holderTable,
+ holder = (PROCLOCK *) hash_search(holderTable,
(void *) &holder,
HASH_REMOVE_SAVED, NULL);
if (!holder)
bool allxids, TransactionId xid)
{
SHM_QUEUE *procHolders = &(proc->procHolders);
- HOLDER *holder;
- HOLDER *nextHolder;
+ PROCLOCK *holder;
+ PROCLOCK *nextHolder;
LWLockId masterLock;
LOCKMETHODTABLE *lockMethodTable;
int i,
LWLockAcquire(masterLock, LW_EXCLUSIVE);
- holder = (HOLDER *) SHMQueueNext(procHolders, procHolders,
- offsetof(HOLDER, procLink));
+ holder = (PROCLOCK *) SHMQueueNext(procHolders, procHolders,
+ offsetof(PROCLOCK, procLink));
while (holder)
{
bool wakeupNeeded = false;
/* Get link first, since we may unlink/delete this holder */
- nextHolder = (HOLDER *) SHMQueueNext(procHolders, &holder->procLink,
- offsetof(HOLDER, procLink));
+ nextHolder = (PROCLOCK *) SHMQueueNext(procHolders, &holder->procLink,
+ offsetof(PROCLOCK, procLink));
Assert(holder->tag.proc == MAKE_OFFSET(proc));
if (!allxids && !TransactionIdEquals(xid, holder->tag.xid))
goto next_item;
- HOLDER_PRINT("LockReleaseAll", holder);
+ PROCLOCK_PRINT("LockReleaseAll", holder);
LOCK_PRINT("LockReleaseAll", lock, 0);
Assert(lock->nRequested >= 0);
Assert(lock->nGranted >= 0);
}
LOCK_PRINT("LockReleaseAll: updated", lock, 0);
- HOLDER_PRINT("LockReleaseAll: deleting", holder);
+ PROCLOCK_PRINT("LockReleaseAll: deleting", holder);
/*
* Remove the holder entry from the linked lists
/*
* remove the holder entry from the hashtable
*/
- holder = (HOLDER *) hash_search(lockMethodTable->holderHash,
+ holder = (PROCLOCK *) hash_search(lockMethodTable->holderHash,
(void *) holder,
HASH_REMOVE,
NULL);
size += hash_estimate_size(max_table_size, sizeof(LOCK));
/* holderHash table */
- size += hash_estimate_size(max_table_size, sizeof(HOLDER));
+ size += hash_estimate_size(max_table_size, sizeof(PROCLOCK));
/*
* Since the lockHash entry count above is only an estimate, add 10%
{
PGPROC *proc;
SHM_QUEUE *procHolders;
- HOLDER *holder;
+ PROCLOCK *holder;
LOCK *lock;
int lockmethod = DEFAULT_LOCKMETHOD;
LOCKMETHODTABLE *lockMethodTable;
if (proc->waitLock)
LOCK_PRINT("DumpLocks: waiting on", proc->waitLock, 0);
- holder = (HOLDER *) SHMQueueNext(procHolders, procHolders,
- offsetof(HOLDER, procLink));
+ holder = (PROCLOCK *) SHMQueueNext(procHolders, procHolders,
+ offsetof(PROCLOCK, procLink));
while (holder)
{
lock = (LOCK *) MAKE_PTR(holder->tag.lock);
- HOLDER_PRINT("DumpLocks", holder);
+ PROCLOCK_PRINT("DumpLocks", holder);
LOCK_PRINT("DumpLocks", lock, 0);
- holder = (HOLDER *) SHMQueueNext(procHolders, &holder->procLink,
- offsetof(HOLDER, procLink));
+ holder = (PROCLOCK *) SHMQueueNext(procHolders, &holder->procLink,
+ offsetof(PROCLOCK, procLink));
}
}
DumpAllLocks(void)
{
PGPROC *proc;
- HOLDER *holder;
+ PROCLOCK *holder;
LOCK *lock;
int lockmethod = DEFAULT_LOCKMETHOD;
LOCKMETHODTABLE *lockMethodTable;
LOCK_PRINT("DumpAllLocks: waiting on", proc->waitLock, 0);
hash_seq_init(&status, holderTable);
- while ((holder = (HOLDER *) hash_seq_search(&status)) != NULL)
+ while ((holder = (PROCLOCK *) hash_seq_search(&status)) != NULL)
{
- HOLDER_PRINT("DumpAllLocks", holder);
+ PROCLOCK_PRINT("DumpAllLocks", holder);
if (holder->tag.lock)
{
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.123 2002/07/18 23:06:20 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.124 2002/07/19 00:17:40 momjian Exp $
*
*-------------------------------------------------------------------------
*/
ProcSleep(LOCKMETHODTABLE *lockMethodTable,
LOCKMODE lockmode,
LOCK *lock,
- HOLDER *holder)
+ PROCLOCK *holder)
{
LWLockId masterLock = lockMethodTable->masterLock;
PROC_QUEUE *waitQueue = &(lock->waitProcs);
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: lock.h,v 1.62 2002/07/18 23:06:20 momjian Exp $
+ * $Id: lock.h,v 1.63 2002/07/19 00:17:40 momjian Exp $
*
*-------------------------------------------------------------------------
*/
* tag -- uniquely identifies the object being locked
* grantMask -- bitmask for all lock types currently granted on this object.
* waitMask -- bitmask for all lock types currently awaited on this object.
- * lockHolders -- list of HOLDER objects for this lock.
+ * lockHolders -- list of PROCLOCK objects for this lock.
* waitProcs -- queue of processes waiting for this lock.
* requested -- count of each lock type currently requested on the lock
* (includes requests already granted!!).
/* data */
int grantMask; /* bitmask for lock types already granted */
int waitMask; /* bitmask for lock types awaited */
- SHM_QUEUE lockHolders; /* list of HOLDER objects assoc. with lock */
+ SHM_QUEUE lockHolders; /* list of PROCLOCK objects assoc. with lock */
PROC_QUEUE waitProcs; /* list of PGPROC objects waiting on lock */
int requested[MAX_LOCKMODES]; /* counts of requested
* locks */
* on the same lockable object. We need to store some per-holder information
* for each such holder (or would-be holder).
*
- * HOLDERTAG is the key information needed to look up a HOLDER item in the
- * holder hashtable. A HOLDERTAG value uniquely identifies a lock holder.
+ * PROCLOCKTAG is the key information needed to look up a PROCLOCK item in the
+ * holder hashtable. A PROCLOCKTAG value uniquely identifies a lock holder.
*
* There are two possible kinds of holder tags: a transaction (identified
* both by the PGPROC of the backend running it, and the xact's own ID) and
* Otherwise, holder objects whose counts have gone to zero are recycled
* as soon as convenient.
*
- * Each HOLDER object is linked into lists for both the associated LOCK object
- * and the owning PGPROC object. Note that the HOLDER is entered into these
+ * Each PROCLOCK object is linked into lists for both the associated LOCK object
+ * and the owning PGPROC object. Note that the PROCLOCK is entered into these
* lists as soon as it is created, even if no lock has yet been granted.
* A PGPROC that is waiting for a lock to be granted will also be linked into
* the lock's waitProcs queue.
*/
-typedef struct HOLDERTAG
+typedef struct PROCLOCKTAG
{
SHMEM_OFFSET lock; /* link to per-lockable-object information */
SHMEM_OFFSET proc; /* link to PGPROC of owning backend */
TransactionId xid; /* xact ID, or InvalidTransactionId */
-} HOLDERTAG;
+} PROCLOCKTAG;
-typedef struct HOLDER
+typedef struct PROCLOCK
{
/* tag */
- HOLDERTAG tag; /* unique identifier of holder object */
+ PROCLOCKTAG tag; /* unique identifier of holder object */
/* data */
int holding[MAX_LOCKMODES]; /* count of locks currently held */
int nHolding; /* total of holding[] array */
SHM_QUEUE lockLink; /* list link for lock's list of holders */
SHM_QUEUE procLink; /* list link for process's list of holders */
-} HOLDER;
+} PROCLOCK;
-#define HOLDER_LOCKMETHOD(holder) \
+#define PROCLOCK_LOCKMETHOD(holder) \
(((LOCK *) MAKE_PTR((holder).tag.lock))->tag.lockmethod)
bool allxids, TransactionId xid);
extern int LockCheckConflicts(LOCKMETHODTABLE *lockMethodTable,
LOCKMODE lockmode,
- LOCK *lock, HOLDER *holder, PGPROC *proc,
+ LOCK *lock, PROCLOCK *holder, PGPROC *proc,
int *myHolding);
-extern void GrantLock(LOCK *lock, HOLDER *holder, LOCKMODE lockmode);
+extern void GrantLock(LOCK *lock, PROCLOCK *holder, LOCKMODE lockmode);
extern void RemoveFromWaitQueue(PGPROC *proc);
extern int LockShmemSize(int maxBackends);
extern bool DeadLockCheck(PGPROC *proc);
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: proc.h,v 1.58 2002/07/13 01:02:14 momjian Exp $
+ * $Id: proc.h,v 1.59 2002/07/19 00:17:40 momjian Exp $
*
*-------------------------------------------------------------------------
*/
/* Info about lock the process is currently waiting for, if any. */
/* waitLock and waitHolder are NULL if not currently waiting. */
LOCK *waitLock; /* Lock object we're sleeping on ... */
- HOLDER *waitHolder; /* Per-holder info for awaited lock */
+ PROCLOCK *waitHolder; /* Per-holder info for awaited lock */
LOCKMODE waitLockMode; /* type of lock we're waiting for */
LOCKMASK heldLocks; /* bitmask for lock types already held on
* this lock object by this backend */
- SHM_QUEUE procHolders; /* list of HOLDER objects for locks held
+ SHM_QUEUE procHolders; /* list of PROCLOCK objects for locks held
* or awaited by this backend */
};
extern void ProcQueueInit(PROC_QUEUE *queue);
extern int ProcSleep(LOCKMETHODTABLE *lockMethodTable, LOCKMODE lockmode,
- LOCK *lock, HOLDER *holder);
+ LOCK *lock, PROCLOCK *holder);
extern PGPROC *ProcWakeup(PGPROC *proc, int errType);
extern void ProcLockWakeup(LOCKMETHODTABLE *lockMethodTable, LOCK *lock);
extern bool LockWaitCancel(void);
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