1 /*-------------------------------------------------------------------------
4 * per-process shared memory data structures
7 * Portions Copyright (c) 1996-2016, 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 "lib/ilist.h"
19 #include "storage/latch.h"
20 #include "storage/lock.h"
21 #include "storage/pg_sema.h"
24 * Each backend advertises up to PGPROC_MAX_CACHED_SUBXIDS TransactionIds
25 * for non-aborted subtransactions of its current top transaction. These
26 * have to be treated as running XIDs by other backends.
28 * We also keep track of whether the cache overflowed (ie, the transaction has
29 * generated at least one subtransaction that didn't fit in the cache).
30 * If none of the caches have overflowed, we can assume that an XID that's not
31 * listed anywhere in the PGPROC array is not a running transaction. Else we
32 * have to look at pg_subtrans.
34 #define PGPROC_MAX_CACHED_SUBXIDS 64 /* XXX guessed-at value */
38 TransactionId xids[PGPROC_MAX_CACHED_SUBXIDS];
41 /* Flags for PGXACT->vacuumFlags */
42 #define PROC_IS_AUTOVACUUM 0x01 /* is it an autovac worker? */
43 #define PROC_IN_VACUUM 0x02 /* currently running lazy vacuum */
44 #define PROC_IN_ANALYZE 0x04 /* currently running analyze */
45 #define PROC_VACUUM_FOR_WRAPAROUND 0x08 /* set by autovac only */
46 #define PROC_IN_LOGICAL_DECODING 0x10 /* currently doing logical
47 * decoding outside xact */
49 /* flags reset at EOXact */
50 #define PROC_VACUUM_STATE_MASK \
51 (PROC_IN_VACUUM | PROC_IN_ANALYZE | PROC_VACUUM_FOR_WRAPAROUND)
54 * We allow a small number of "weak" relation locks (AccesShareLock,
55 * RowShareLock, RowExclusiveLock) to be recorded in the PGPROC structure
56 * rather than the main lock table. This eases contention on the lock
57 * manager LWLocks. See storage/lmgr/README for additional details.
59 #define FP_LOCK_SLOTS_PER_BACKEND 16
62 * An invalid pgprocno. Must be larger than the maximum number of PGPROC
63 * structures we could possibly have. See comments for MAX_BACKENDS.
65 #define INVALID_PGPROCNO PG_INT32_MAX
68 * Each backend has a PGPROC struct in shared memory. There is also a list of
69 * currently-unused PGPROC structs that will be reallocated to new backends.
71 * links: list link for any list the PGPROC is in. When waiting for a lock,
72 * the PGPROC is linked into that lock's waitProcs queue. A recycled PGPROC
73 * is linked into ProcGlobal's freeProcs list.
75 * Note: twophase.c also sets up a dummy PGPROC struct for each currently
76 * prepared transaction. These PGPROCs appear in the ProcArray data structure
77 * so that the prepared transactions appear to be still running and are
78 * correctly shown as holding locks. A prepared transaction PGPROC can be
79 * distinguished from a real one at need by the fact that it has pid == 0.
80 * The semaphore and lock-activity fields in a prepared-xact PGPROC are unused,
81 * but its myProcLocks[] lists are valid.
85 /* proc->links MUST BE FIRST IN STRUCT (see ProcSleep,ProcWakeup,etc) */
86 SHM_QUEUE links; /* list link if process is in a list */
87 PGPROC **procgloballist; /* procglobal list that owns this PGPROC */
89 PGSemaphoreData sem; /* ONE semaphore to sleep on */
90 int waitStatus; /* STATUS_WAITING, STATUS_OK or STATUS_ERROR */
92 Latch procLatch; /* generic latch for process */
94 LocalTransactionId lxid; /* local id of top-level transaction currently
95 * being executed by this proc, if running;
96 * else InvalidLocalTransactionId */
97 int pid; /* Backend's process ID; 0 if prepared xact */
100 /* These fields are zero while a backend is still starting up: */
101 BackendId backendId; /* This backend's backend ID (if assigned) */
102 Oid databaseId; /* OID of database this backend is using */
103 Oid roleId; /* OID of role using this backend */
106 * While in hot standby mode, shows that a conflict signal has been sent
107 * for the current transaction. Set/cleared while holding ProcArrayLock,
108 * though not required. Accessed without lock, if needed.
110 bool recoveryConflictPending;
112 /* Info about LWLock the process is currently waiting for, if any. */
113 bool lwWaiting; /* true if waiting for an LW lock */
114 uint8 lwWaitMode; /* lwlock mode being waited for */
115 dlist_node lwWaitLink; /* position in LW lock wait list */
117 /* Info about lock the process is currently waiting for, if any. */
118 /* waitLock and waitProcLock are NULL if not currently waiting. */
119 LOCK *waitLock; /* Lock object we're sleeping on ... */
120 PROCLOCK *waitProcLock; /* Per-holder info for awaited lock */
121 LOCKMODE waitLockMode; /* type of lock we're waiting for */
122 LOCKMASK heldLocks; /* bitmask for lock types already held on this
123 * lock object by this backend */
126 * Info to allow us to wait for synchronous replication, if needed.
127 * waitLSN is InvalidXLogRecPtr if not waiting; set only by user backend.
128 * syncRepState must not be touched except by owning process or WALSender.
129 * syncRepLinks used only while holding SyncRepLock.
131 XLogRecPtr waitLSN; /* waiting for this LSN or higher */
132 int syncRepState; /* wait state for sync rep */
133 SHM_QUEUE syncRepLinks; /* list link if process is in syncrep queue */
136 * All PROCLOCK objects for locks held or awaited by this backend are
137 * linked into one of these lists, according to the partition number of
140 SHM_QUEUE myProcLocks[NUM_LOCK_PARTITIONS];
142 struct XidCache subxids; /* cache for subtransaction XIDs */
144 /* Support for group XID clearing. */
146 pg_atomic_uint32 nextClearXidElem;
147 TransactionId backendLatestXid;
149 /* Per-backend LWLock. Protects fields below. */
150 LWLock *backendLock; /* protects the fields below */
152 /* Lock manager data, recording fast-path locks taken by this backend. */
153 uint64 fpLockBits; /* lock modes held for each fast-path slot */
154 Oid fpRelId[FP_LOCK_SLOTS_PER_BACKEND]; /* slots for rel oids */
155 bool fpVXIDLock; /* are we holding a fast-path VXID lock? */
156 LocalTransactionId fpLocalTransactionId; /* lxid for fast-path VXID
160 /* NOTE: "typedef struct PGPROC PGPROC" appears in storage/lock.h. */
163 extern PGDLLIMPORT PGPROC *MyProc;
164 extern PGDLLIMPORT struct PGXACT *MyPgXact;
167 * Prior to PostgreSQL 9.2, the fields below were stored as part of the
168 * PGPROC. However, benchmarking revealed that packing these particular
169 * members into a separate array as tightly as possible sped up GetSnapshotData
170 * considerably on systems with many CPU cores, by reducing the number of
171 * cache lines needing to be fetched. Thus, think very carefully before adding
172 * anything else here.
174 typedef struct PGXACT
176 TransactionId xid; /* id of top-level transaction currently being
177 * executed by this proc, if running and XID
178 * is assigned; else InvalidTransactionId */
180 TransactionId xmin; /* minimal running XID as it was when we were
181 * starting our xact, excluding LAZY VACUUM:
182 * vacuum must not remove tuples deleted by
185 uint8 vacuumFlags; /* vacuum-related flags, see above */
187 bool delayChkpt; /* true if this proc delays checkpoint start;
188 * previously called InCommit */
194 * There is one ProcGlobal struct for the whole database cluster.
196 typedef struct PROC_HDR
198 /* Array of PGPROC structures (not including dummies for prepared txns) */
200 /* Array of PGXACT structures (not including dummies for prepared txns) */
202 /* Length of allProcs array */
204 /* Head of list of free PGPROC structures */
206 /* Head of list of autovacuum's free PGPROC structures */
207 PGPROC *autovacFreeProcs;
208 /* Head of list of bgworker free PGPROC structures */
209 PGPROC *bgworkerFreeProcs;
210 /* First pgproc waiting for group XID clear */
211 pg_atomic_uint32 firstClearXidElem;
212 /* WALWriter process's latch */
213 Latch *walwriterLatch;
214 /* Checkpointer process's latch */
215 Latch *checkpointerLatch;
216 /* Current shared estimate of appropriate spins_per_delay value */
218 /* The proc of the Startup process, since not in ProcArray */
221 /* Buffer id of the buffer that Startup process waits for pin on, or -1 */
222 int startupBufferPinWaitBufId;
225 extern PROC_HDR *ProcGlobal;
227 extern PGPROC *PreparedXactProcs;
230 * We set aside some extra PGPROC structures for auxiliary processes,
231 * ie things that aren't full-fledged backends but need shmem access.
233 * Background writer, checkpointer and WAL writer run during normal operation.
234 * Startup process and WAL receiver also consume 2 slots, but WAL writer is
235 * launched only after startup has exited, so we only need 4 slots.
237 #define NUM_AUXILIARY_PROCS 4
240 /* configurable options */
241 extern int DeadlockTimeout;
242 extern int StatementTimeout;
243 extern int LockTimeout;
244 extern bool log_lock_waits;
248 * Function Prototypes
250 extern int ProcGlobalSemas(void);
251 extern Size ProcGlobalShmemSize(void);
252 extern void InitProcGlobal(void);
253 extern void InitProcess(void);
254 extern void InitProcessPhase2(void);
255 extern void InitAuxiliaryProcess(void);
257 extern void PublishStartupProcessInformation(void);
258 extern void SetStartupBufferPinWaitBufId(int bufid);
259 extern int GetStartupBufferPinWaitBufId(void);
261 extern bool HaveNFreeProcs(int n);
262 extern void ProcReleaseLocks(bool isCommit);
264 extern void ProcQueueInit(PROC_QUEUE *queue);
265 extern int ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable);
266 extern PGPROC *ProcWakeup(PGPROC *proc, int waitStatus);
267 extern void ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock);
268 extern void CheckDeadLockAlert(void);
269 extern bool IsWaitingForLock(void);
270 extern void LockErrorCleanup(void);
272 extern void ProcWaitForSignal(void);
273 extern void ProcSendSignal(int pid);