1 /*-------------------------------------------------------------------------
4 * per-process shared memory data structures
7 * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
10 * src/include/storage/proc.h
12 *-------------------------------------------------------------------------
17 #include "access/xlogdefs.h"
18 #include "storage/latch.h"
19 #include "storage/lock.h"
20 #include "storage/pg_sema.h"
23 * Each backend advertises up to PGPROC_MAX_CACHED_SUBXIDS TransactionIds
24 * for non-aborted subtransactions of its current top transaction. These
25 * have to be treated as running XIDs by other backends.
27 * We also keep track of whether the cache overflowed (ie, the transaction has
28 * generated at least one subtransaction that didn't fit in the cache).
29 * If none of the caches have overflowed, we can assume that an XID that's not
30 * listed anywhere in the PGPROC array is not a running transaction. Else we
31 * have to look at pg_subtrans.
33 #define PGPROC_MAX_CACHED_SUBXIDS 64 /* XXX guessed-at value */
37 TransactionId xids[PGPROC_MAX_CACHED_SUBXIDS];
40 /* Flags for PGXACT->vacuumFlags */
41 #define PROC_IS_AUTOVACUUM 0x01 /* is it an autovac worker? */
42 #define PROC_IN_VACUUM 0x02 /* currently running lazy vacuum */
43 #define PROC_IN_ANALYZE 0x04 /* currently running analyze */
44 #define PROC_VACUUM_FOR_WRAPAROUND 0x08 /* set by autovac only */
45 #define PROC_IN_LOGICAL_DECODING 0x10 /* currently doing logical
48 /* flags reset at EOXact */
49 #define PROC_VACUUM_STATE_MASK \
50 (PROC_IN_VACUUM | PROC_IN_ANALYZE | PROC_VACUUM_FOR_WRAPAROUND)
53 * We allow a small number of "weak" relation locks (AccesShareLock,
54 * RowShareLock, RowExclusiveLock) to be recorded in the PGPROC structure
55 * rather than the main lock table. This eases contention on the lock
56 * manager LWLocks. See storage/lmgr/README for additional details.
58 #define FP_LOCK_SLOTS_PER_BACKEND 16
61 * Each backend has a PGPROC struct in shared memory. There is also a list of
62 * currently-unused PGPROC structs that will be reallocated to new backends.
64 * links: list link for any list the PGPROC is in. When waiting for a lock,
65 * the PGPROC is linked into that lock's waitProcs queue. A recycled PGPROC
66 * is linked into ProcGlobal's freeProcs list.
68 * Note: twophase.c also sets up a dummy PGPROC struct for each currently
69 * prepared transaction. These PGPROCs appear in the ProcArray data structure
70 * so that the prepared transactions appear to be still running and are
71 * correctly shown as holding locks. A prepared transaction PGPROC can be
72 * distinguished from a real one at need by the fact that it has pid == 0.
73 * The semaphore and lock-activity fields in a prepared-xact PGPROC are unused,
74 * but its myProcLocks[] lists are valid.
78 /* proc->links MUST BE FIRST IN STRUCT (see ProcSleep,ProcWakeup,etc) */
79 SHM_QUEUE links; /* list link if process is in a list */
81 PGSemaphoreData sem; /* ONE semaphore to sleep on */
82 int waitStatus; /* STATUS_WAITING, STATUS_OK or STATUS_ERROR */
84 Latch procLatch; /* generic latch for process */
86 LocalTransactionId lxid; /* local id of top-level transaction currently
87 * being executed by this proc, if running;
88 * else InvalidLocalTransactionId */
89 int pid; /* Backend's process ID; 0 if prepared xact */
92 /* These fields are zero while a backend is still starting up: */
93 BackendId backendId; /* This backend's backend ID (if assigned) */
94 Oid databaseId; /* OID of database this backend is using */
95 Oid roleId; /* OID of role using this backend */
98 * While in hot standby mode, shows that a conflict signal has been sent
99 * for the current transaction. Set/cleared while holding ProcArrayLock,
100 * though not required. Accessed without lock, if needed.
102 bool recoveryConflictPending;
104 /* Info about LWLock the process is currently waiting for, if any. */
105 bool lwWaiting; /* true if waiting for an LW lock */
106 uint8 lwWaitMode; /* lwlock mode being waited for */
107 struct PGPROC *lwWaitLink; /* next waiter for same LW lock */
109 /* Info about lock the process is currently waiting for, if any. */
110 /* waitLock and waitProcLock are NULL if not currently waiting. */
111 LOCK *waitLock; /* Lock object we're sleeping on ... */
112 PROCLOCK *waitProcLock; /* Per-holder info for awaited lock */
113 LOCKMODE waitLockMode; /* type of lock we're waiting for */
114 LOCKMASK heldLocks; /* bitmask for lock types already held on this
115 * lock object by this backend */
118 * Info to allow us to wait for synchronous replication, if needed.
119 * waitLSN is InvalidXLogRecPtr if not waiting; set only by user backend.
120 * syncRepState must not be touched except by owning process or WALSender.
121 * syncRepLinks used only while holding SyncRepLock.
123 XLogRecPtr waitLSN; /* waiting for this LSN or higher */
124 int syncRepState; /* wait state for sync rep */
125 SHM_QUEUE syncRepLinks; /* list link if process is in syncrep queue */
128 * All PROCLOCK objects for locks held or awaited by this backend are
129 * linked into one of these lists, according to the partition number of
132 SHM_QUEUE myProcLocks[NUM_LOCK_PARTITIONS];
134 struct XidCache subxids; /* cache for subtransaction XIDs */
136 /* Per-backend LWLock. Protects fields below. */
137 LWLock *backendLock; /* protects the fields below */
139 /* Lock manager data, recording fast-path locks taken by this backend. */
140 uint64 fpLockBits; /* lock modes held for each fast-path slot */
141 Oid fpRelId[FP_LOCK_SLOTS_PER_BACKEND]; /* slots for rel oids */
142 bool fpVXIDLock; /* are we holding a fast-path VXID lock? */
143 LocalTransactionId fpLocalTransactionId; /* lxid for fast-path VXID
147 /* NOTE: "typedef struct PGPROC PGPROC" appears in storage/lock.h. */
150 extern PGDLLIMPORT PGPROC *MyProc;
151 extern PGDLLIMPORT struct PGXACT *MyPgXact;
154 * Prior to PostgreSQL 9.2, the fields below were stored as part of the
155 * PGPROC. However, benchmarking revealed that packing these particular
156 * members into a separate array as tightly as possible sped up GetSnapshotData
157 * considerably on systems with many CPU cores, by reducing the number of
158 * cache lines needing to be fetched. Thus, think very carefully before adding
159 * anything else here.
161 typedef struct PGXACT
163 TransactionId xid; /* id of top-level transaction currently being
164 * executed by this proc, if running and XID
165 * is assigned; else InvalidTransactionId */
167 TransactionId xmin; /* minimal running XID as it was when we were
168 * starting our xact, excluding LAZY VACUUM:
169 * vacuum must not remove tuples deleted by
172 uint8 vacuumFlags; /* vacuum-related flags, see above */
174 bool delayChkpt; /* true if this proc delays checkpoint start;
175 * previously called InCommit */
181 * There is one ProcGlobal struct for the whole database cluster.
183 typedef struct PROC_HDR
185 /* Array of PGPROC structures (not including dummies for prepared txns) */
187 /* Array of PGXACT structures (not including dummies for prepared txns) */
189 /* Length of allProcs array */
191 /* Head of list of free PGPROC structures */
193 /* Head of list of autovacuum's free PGPROC structures */
194 PGPROC *autovacFreeProcs;
195 /* Head of list of bgworker free PGPROC structures */
196 PGPROC *bgworkerFreeProcs;
197 /* WALWriter process's latch */
198 Latch *walwriterLatch;
199 /* Checkpointer process's latch */
200 Latch *checkpointerLatch;
201 /* Current shared estimate of appropriate spins_per_delay value */
203 /* The proc of the Startup process, since not in ProcArray */
206 /* Buffer id of the buffer that Startup process waits for pin on, or -1 */
207 int startupBufferPinWaitBufId;
210 extern PROC_HDR *ProcGlobal;
212 extern PGPROC *PreparedXactProcs;
215 * We set aside some extra PGPROC structures for auxiliary processes,
216 * ie things that aren't full-fledged backends but need shmem access.
218 * Background writer, checkpointer and WAL writer run during normal operation.
219 * Startup process and WAL receiver also consume 2 slots, but WAL writer is
220 * launched only after startup has exited, so we only need 4 slots.
222 #define NUM_AUXILIARY_PROCS 4
225 /* configurable options */
226 extern int DeadlockTimeout;
227 extern int StatementTimeout;
228 extern int LockTimeout;
229 extern bool log_lock_waits;
233 * Function Prototypes
235 extern int ProcGlobalSemas(void);
236 extern Size ProcGlobalShmemSize(void);
237 extern void InitProcGlobal(void);
238 extern void InitProcess(void);
239 extern void InitProcessPhase2(void);
240 extern void InitAuxiliaryProcess(void);
242 extern void PublishStartupProcessInformation(void);
243 extern void SetStartupBufferPinWaitBufId(int bufid);
244 extern int GetStartupBufferPinWaitBufId(void);
246 extern bool HaveNFreeProcs(int n);
247 extern void ProcReleaseLocks(bool isCommit);
249 extern void ProcQueueInit(PROC_QUEUE *queue);
250 extern int ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable);
251 extern PGPROC *ProcWakeup(PGPROC *proc, int waitStatus);
252 extern void ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock);
253 extern void CheckDeadLock(void);
254 extern bool IsWaitingForLock(void);
255 extern void LockErrorCleanup(void);
257 extern void ProcWaitForSignal(void);
258 extern void ProcSendSignal(int pid);