1 /*------------------------------------------------------------------------- 2 * 3 * proc.h 4 * per-process shared memory data structures 5 * 6 * 7 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group 8 * Portions Copyright (c) 1994, Regents of the University of California 9 * 10 * src/include/storage/proc.h 11 * 12 *------------------------------------------------------------------------- 13 */ 14 #ifndef _PROC_H_ 15 #define _PROC_H_ 16 17 #include "access/clog.h" 18 #include "access/xlogdefs.h" 19 #include "lib/ilist.h" 20 #include "storage/latch.h" 21 #include "storage/lock.h" 22 #include "storage/pg_sema.h" 23 #include "storage/proclist_types.h" 24 25 /* 26 * Each backend advertises up to PGPROC_MAX_CACHED_SUBXIDS TransactionIds 27 * for non-aborted subtransactions of its current top transaction. These 28 * have to be treated as running XIDs by other backends. 29 * 30 * We also keep track of whether the cache overflowed (ie, the transaction has 31 * generated at least one subtransaction that didn't fit in the cache). 32 * If none of the caches have overflowed, we can assume that an XID that's not 33 * listed anywhere in the PGPROC array is not a running transaction. Else we 34 * have to look at pg_subtrans. 35 */ 36 #define PGPROC_MAX_CACHED_SUBXIDS 64 /* XXX guessed-at value */ 37 38 struct XidCache 39 { 40 TransactionId xids[PGPROC_MAX_CACHED_SUBXIDS]; 41 }; 42 43 /* 44 * Flags for PGXACT->vacuumFlags 45 * 46 * Note: If you modify these flags, you need to modify PROCARRAY_XXX flags 47 * in src/include/storage/procarray.h. 48 * 49 * PROC_RESERVED may later be assigned for use in vacuumFlags, but its value is 50 * used for PROCARRAY_SLOTS_XMIN in procarray.h, so GetOldestXmin won't be able 51 * to match and ignore processes with this flag set. 52 */ 53 #define PROC_IS_AUTOVACUUM 0x01 /* is it an autovac worker? */ 54 #define PROC_IN_VACUUM 0x02 /* currently running lazy vacuum */ 55 #define PROC_IN_ANALYZE 0x04 /* currently running analyze */ 56 #define PROC_VACUUM_FOR_WRAPAROUND 0x08 /* set by autovac only */ 57 #define PROC_IN_LOGICAL_DECODING 0x10 /* currently doing logical 58 * decoding outside xact */ 59 #define PROC_RESERVED 0x20 /* reserved for procarray */ 60 61 /* flags reset at EOXact */ 62 #define PROC_VACUUM_STATE_MASK \ 63 (PROC_IN_VACUUM | PROC_IN_ANALYZE | PROC_VACUUM_FOR_WRAPAROUND) 64 65 /* 66 * We allow a small number of "weak" relation locks (AccessShareLock, 67 * RowShareLock, RowExclusiveLock) to be recorded in the PGPROC structure 68 * rather than the main lock table. This eases contention on the lock 69 * manager LWLocks. See storage/lmgr/README for additional details. 70 */ 71 #define FP_LOCK_SLOTS_PER_BACKEND 16 72 73 /* 74 * An invalid pgprocno. Must be larger than the maximum number of PGPROC 75 * structures we could possibly have. See comments for MAX_BACKENDS. 76 */ 77 #define INVALID_PGPROCNO PG_INT32_MAX 78 79 /* 80 * Each backend has a PGPROC struct in shared memory. There is also a list of 81 * currently-unused PGPROC structs that will be reallocated to new backends. 82 * 83 * links: list link for any list the PGPROC is in. When waiting for a lock, 84 * the PGPROC is linked into that lock's waitProcs queue. A recycled PGPROC 85 * is linked into ProcGlobal's freeProcs list. 86 * 87 * Note: twophase.c also sets up a dummy PGPROC struct for each currently 88 * prepared transaction. These PGPROCs appear in the ProcArray data structure 89 * so that the prepared transactions appear to be still running and are 90 * correctly shown as holding locks. A prepared transaction PGPROC can be 91 * distinguished from a real one at need by the fact that it has pid == 0. 92 * The semaphore and lock-activity fields in a prepared-xact PGPROC are unused, 93 * but its myProcLocks[] lists are valid. 94 */ 95 struct PGPROC 96 { 97 /* proc->links MUST BE FIRST IN STRUCT (see ProcSleep,ProcWakeup,etc) */ 98 SHM_QUEUE links; /* list link if process is in a list */ 99 PGPROC **procgloballist; /* procglobal list that owns this PGPROC */ 100 101 PGSemaphore sem; /* ONE semaphore to sleep on */ 102 int waitStatus; /* STATUS_WAITING, STATUS_OK or STATUS_ERROR */ 103 104 Latch procLatch; /* generic latch for process */ 105 106 LocalTransactionId lxid; /* local id of top-level transaction currently 107 * being executed by this proc, if running; 108 * else InvalidLocalTransactionId */ 109 int pid; /* Backend's process ID; 0 if prepared xact */ 110 int pgprocno; 111 112 /* These fields are zero while a backend is still starting up: */ 113 BackendId backendId; /* This backend's backend ID (if assigned) */ 114 Oid databaseId; /* OID of database this backend is using */ 115 Oid roleId; /* OID of role using this backend */ 116 117 Oid tempNamespaceId; /* OID of temp schema this backend is 118 * using */ 119 120 bool isBackgroundWorker; /* true if background worker. */ 121 122 /* 123 * While in hot standby mode, shows that a conflict signal has been sent 124 * for the current transaction. Set/cleared while holding ProcArrayLock, 125 * though not required. Accessed without lock, if needed. 126 */ 127 bool recoveryConflictPending; 128 129 /* Info about LWLock the process is currently waiting for, if any. */ 130 bool lwWaiting; /* true if waiting for an LW lock */ 131 uint8 lwWaitMode; /* lwlock mode being waited for */ 132 proclist_node lwWaitLink; /* position in LW lock wait list */ 133 134 /* Support for condition variables. */ 135 proclist_node cvWaitLink; /* position in CV wait list */ 136 137 /* Info about lock the process is currently waiting for, if any. */ 138 /* waitLock and waitProcLock are NULL if not currently waiting. */ 139 LOCK *waitLock; /* Lock object we're sleeping on ... */ 140 PROCLOCK *waitProcLock; /* Per-holder info for awaited lock */ 141 LOCKMODE waitLockMode; /* type of lock we're waiting for */ 142 LOCKMASK heldLocks; /* bitmask for lock types already held on this 143 * lock object by this backend */ 144 145 bool delayChkpt; /* true if this proc delays checkpoint start */ 146 147 /* 148 * Info to allow us to wait for synchronous replication, if needed. 149 * waitLSN is InvalidXLogRecPtr if not waiting; set only by user backend. 150 * syncRepState must not be touched except by owning process or WALSender. 151 * syncRepLinks used only while holding SyncRepLock. 152 */ 153 XLogRecPtr waitLSN; /* waiting for this LSN or higher */ 154 int syncRepState; /* wait state for sync rep */ 155 SHM_QUEUE syncRepLinks; /* list link if process is in syncrep queue */ 156 157 /* 158 * All PROCLOCK objects for locks held or awaited by this backend are 159 * linked into one of these lists, according to the partition number of 160 * their lock. 161 */ 162 SHM_QUEUE myProcLocks[NUM_LOCK_PARTITIONS]; 163 164 struct XidCache subxids; /* cache for subtransaction XIDs */ 165 166 /* Support for group XID clearing. */ 167 /* true, if member of ProcArray group waiting for XID clear */ 168 bool procArrayGroupMember; 169 /* next ProcArray group member waiting for XID clear */ 170 pg_atomic_uint32 procArrayGroupNext; 171 172 /* 173 * latest transaction id among the transaction's main XID and 174 * subtransactions 175 */ 176 TransactionId procArrayGroupMemberXid; 177 178 uint32 wait_event_info; /* proc's wait information */ 179 180 /* Support for group transaction status update. */ 181 bool clogGroupMember; /* true, if member of clog group */ 182 pg_atomic_uint32 clogGroupNext; /* next clog group member */ 183 TransactionId clogGroupMemberXid; /* transaction id of clog group member */ 184 XidStatus clogGroupMemberXidStatus; /* transaction status of clog 185 * group member */ 186 int clogGroupMemberPage; /* clog page corresponding to 187 * transaction id of clog group member */ 188 XLogRecPtr clogGroupMemberLsn; /* WAL location of commit record for clog 189 * group member */ 190 191 /* Lock manager data, recording fast-path locks taken by this backend. */ 192 LWLock fpInfoLock; /* protects per-backend fast-path state */ 193 uint64 fpLockBits; /* lock modes held for each fast-path slot */ 194 Oid fpRelId[FP_LOCK_SLOTS_PER_BACKEND]; /* slots for rel oids */ 195 bool fpVXIDLock; /* are we holding a fast-path VXID lock? */ 196 LocalTransactionId fpLocalTransactionId; /* lxid for fast-path VXID 197 * lock */ 198 199 /* 200 * Support for lock groups. Use LockHashPartitionLockByProc on the group 201 * leader to get the LWLock protecting these fields. 202 */ 203 PGPROC *lockGroupLeader; /* lock group leader, if I'm a member */ 204 dlist_head lockGroupMembers; /* list of members, if I'm a leader */ 205 dlist_node lockGroupLink; /* my member link, if I'm a member */ 206 }; 207 208 /* NOTE: "typedef struct PGPROC PGPROC" appears in storage/lock.h. */ 209 210 211 extern PGDLLIMPORT PGPROC *MyProc; 212 extern PGDLLIMPORT struct PGXACT *MyPgXact; 213 214 /* 215 * Prior to PostgreSQL 9.2, the fields below were stored as part of the 216 * PGPROC. However, benchmarking revealed that packing these particular 217 * members into a separate array as tightly as possible sped up GetSnapshotData 218 * considerably on systems with many CPU cores, by reducing the number of 219 * cache lines needing to be fetched. Thus, think very carefully before adding 220 * anything else here. 221 */ 222 typedef struct PGXACT 223 { 224 TransactionId xid; /* id of top-level transaction currently being 225 * executed by this proc, if running and XID 226 * is assigned; else InvalidTransactionId */ 227 228 TransactionId xmin; /* minimal running XID as it was when we were 229 * starting our xact, excluding LAZY VACUUM: 230 * vacuum must not remove tuples deleted by 231 * xid >= xmin ! */ 232 233 uint8 vacuumFlags; /* vacuum-related flags, see above */ 234 bool overflowed; 235 236 uint8 nxids; 237 } PGXACT; 238 239 /* 240 * There is one ProcGlobal struct for the whole database cluster. 241 */ 242 typedef struct PROC_HDR 243 { 244 /* Array of PGPROC structures (not including dummies for prepared txns) */ 245 PGPROC *allProcs; 246 /* Array of PGXACT structures (not including dummies for prepared txns) */ 247 PGXACT *allPgXact; 248 /* Length of allProcs array */ 249 uint32 allProcCount; 250 /* Head of list of free PGPROC structures */ 251 PGPROC *freeProcs; 252 /* Head of list of autovacuum's free PGPROC structures */ 253 PGPROC *autovacFreeProcs; 254 /* Head of list of bgworker free PGPROC structures */ 255 PGPROC *bgworkerFreeProcs; 256 /* Head of list of walsender free PGPROC structures */ 257 PGPROC *walsenderFreeProcs; 258 /* First pgproc waiting for group XID clear */ 259 pg_atomic_uint32 procArrayGroupFirst; 260 /* First pgproc waiting for group transaction status update */ 261 pg_atomic_uint32 clogGroupFirst; 262 /* WALWriter process's latch */ 263 Latch *walwriterLatch; 264 /* Checkpointer process's latch */ 265 Latch *checkpointerLatch; 266 /* Current shared estimate of appropriate spins_per_delay value */ 267 int spins_per_delay; 268 /* The proc of the Startup process, since not in ProcArray */ 269 PGPROC *startupProc; 270 int startupProcPid; 271 /* Buffer id of the buffer that Startup process waits for pin on, or -1 */ 272 int startupBufferPinWaitBufId; 273 } PROC_HDR; 274 275 extern PGDLLIMPORT PROC_HDR *ProcGlobal; 276 277 extern PGPROC *PreparedXactProcs; 278 279 /* Accessor for PGPROC given a pgprocno. */ 280 #define GetPGProcByNumber(n) (&ProcGlobal->allProcs[(n)]) 281 282 /* 283 * We set aside some extra PGPROC structures for auxiliary processes, 284 * ie things that aren't full-fledged backends but need shmem access. 285 * 286 * Background writer, checkpointer and WAL writer run during normal operation. 287 * Startup process and WAL receiver also consume 2 slots, but WAL writer is 288 * launched only after startup has exited, so we only need 4 slots. 289 */ 290 #define NUM_AUXILIARY_PROCS 4 291 292 /* configurable options */ 293 extern PGDLLIMPORT int DeadlockTimeout; 294 extern PGDLLIMPORT int StatementTimeout; 295 extern PGDLLIMPORT int LockTimeout; 296 extern PGDLLIMPORT int IdleInTransactionSessionTimeout; 297 extern bool log_lock_waits; 298 299 300 /* 301 * Function Prototypes 302 */ 303 extern int ProcGlobalSemas(void); 304 extern Size ProcGlobalShmemSize(void); 305 extern void InitProcGlobal(void); 306 extern void InitProcess(void); 307 extern void InitProcessPhase2(void); 308 extern void InitAuxiliaryProcess(void); 309 310 extern void PublishStartupProcessInformation(void); 311 extern void SetStartupBufferPinWaitBufId(int bufid); 312 extern int GetStartupBufferPinWaitBufId(void); 313 314 extern bool HaveNFreeProcs(int n); 315 extern void ProcReleaseLocks(bool isCommit); 316 317 extern void ProcQueueInit(PROC_QUEUE *queue); 318 extern int ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable); 319 extern PGPROC *ProcWakeup(PGPROC *proc, int waitStatus); 320 extern void ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock); 321 extern void CheckDeadLockAlert(void); 322 extern bool IsWaitingForLock(void); 323 extern void LockErrorCleanup(void); 324 325 extern void ProcWaitForSignal(uint32 wait_event_info); 326 extern void ProcSendSignal(int pid); 327 328 extern PGPROC *AuxiliaryPidGetProc(int pid); 329 330 extern void BecomeLockGroupLeader(void); 331 extern bool BecomeLockGroupMember(PGPROC *leader, int pid); 332 333 #endif /* _PROC_H_ */ 334