1 /*------------------------------------------------------------------------- 2 * 3 * proc.h 4 * per-process shared memory data structures 5 * 6 * 7 * Portions Copyright (c) 1996-2017, 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/xlogdefs.h" 18 #include "lib/ilist.h" 19 #include "storage/latch.h" 20 #include "storage/lock.h" 21 #include "storage/pg_sema.h" 22 #include "storage/proclist_types.h" 23 24 /* 25 * Each backend advertises up to PGPROC_MAX_CACHED_SUBXIDS TransactionIds 26 * for non-aborted subtransactions of its current top transaction. These 27 * have to be treated as running XIDs by other backends. 28 * 29 * We also keep track of whether the cache overflowed (ie, the transaction has 30 * generated at least one subtransaction that didn't fit in the cache). 31 * If none of the caches have overflowed, we can assume that an XID that's not 32 * listed anywhere in the PGPROC array is not a running transaction. Else we 33 * have to look at pg_subtrans. 34 */ 35 #define PGPROC_MAX_CACHED_SUBXIDS 64 /* XXX guessed-at value */ 36 37 struct XidCache 38 { 39 TransactionId xids[PGPROC_MAX_CACHED_SUBXIDS]; 40 }; 41 42 /* 43 * Flags for PGXACT->vacuumFlags 44 * 45 * Note: If you modify these flags, you need to modify PROCARRAY_XXX flags 46 * in src/include/storage/procarray.h. 47 * 48 * PROC_RESERVED may later be assigned for use in vacuumFlags, but its value is 49 * used for PROCARRAY_SLOTS_XMIN in procarray.h, so GetOldestXmin won't be able 50 * to match and ignore processes with this flag set. 51 */ 52 #define PROC_IS_AUTOVACUUM 0x01 /* is it an autovac worker? */ 53 #define PROC_IN_VACUUM 0x02 /* currently running lazy vacuum */ 54 #define PROC_IN_ANALYZE 0x04 /* currently running analyze */ 55 #define PROC_VACUUM_FOR_WRAPAROUND 0x08 /* set by autovac only */ 56 #define PROC_IN_LOGICAL_DECODING 0x10 /* currently doing logical 57 * decoding outside xact */ 58 #define PROC_RESERVED 0x20 /* reserved for procarray */ 59 60 /* flags reset at EOXact */ 61 #define PROC_VACUUM_STATE_MASK \ 62 (PROC_IN_VACUUM | PROC_IN_ANALYZE | PROC_VACUUM_FOR_WRAPAROUND) 63 64 /* 65 * We allow a small number of "weak" relation locks (AccesShareLock, 66 * RowShareLock, RowExclusiveLock) to be recorded in the PGPROC structure 67 * rather than the main lock table. This eases contention on the lock 68 * manager LWLocks. See storage/lmgr/README for additional details. 69 */ 70 #define FP_LOCK_SLOTS_PER_BACKEND 16 71 72 /* 73 * An invalid pgprocno. Must be larger than the maximum number of PGPROC 74 * structures we could possibly have. See comments for MAX_BACKENDS. 75 */ 76 #define INVALID_PGPROCNO PG_INT32_MAX 77 78 /* 79 * Each backend has a PGPROC struct in shared memory. There is also a list of 80 * currently-unused PGPROC structs that will be reallocated to new backends. 81 * 82 * links: list link for any list the PGPROC is in. When waiting for a lock, 83 * the PGPROC is linked into that lock's waitProcs queue. A recycled PGPROC 84 * is linked into ProcGlobal's freeProcs list. 85 * 86 * Note: twophase.c also sets up a dummy PGPROC struct for each currently 87 * prepared transaction. These PGPROCs appear in the ProcArray data structure 88 * so that the prepared transactions appear to be still running and are 89 * correctly shown as holding locks. A prepared transaction PGPROC can be 90 * distinguished from a real one at need by the fact that it has pid == 0. 91 * The semaphore and lock-activity fields in a prepared-xact PGPROC are unused, 92 * but its myProcLocks[] lists are valid. 93 */ 94 struct PGPROC 95 { 96 /* proc->links MUST BE FIRST IN STRUCT (see ProcSleep,ProcWakeup,etc) */ 97 SHM_QUEUE links; /* list link if process is in a list */ 98 PGPROC **procgloballist; /* procglobal list that owns this PGPROC */ 99 100 PGSemaphore sem; /* ONE semaphore to sleep on */ 101 int waitStatus; /* STATUS_WAITING, STATUS_OK or STATUS_ERROR */ 102 103 Latch procLatch; /* generic latch for process */ 104 105 LocalTransactionId lxid; /* local id of top-level transaction currently 106 * being executed by this proc, if running; 107 * else InvalidLocalTransactionId */ 108 int pid; /* Backend's process ID; 0 if prepared xact */ 109 int pgprocno; 110 111 /* These fields are zero while a backend is still starting up: */ 112 BackendId backendId; /* This backend's backend ID (if assigned) */ 113 Oid databaseId; /* OID of database this backend is using */ 114 Oid roleId; /* OID of role using this backend */ 115 116 bool isBackgroundWorker; /* true if background worker. */ 117 118 /* 119 * While in hot standby mode, shows that a conflict signal has been sent 120 * for the current transaction. Set/cleared while holding ProcArrayLock, 121 * though not required. Accessed without lock, if needed. 122 */ 123 bool recoveryConflictPending; 124 125 /* Info about LWLock the process is currently waiting for, if any. */ 126 bool lwWaiting; /* true if waiting for an LW lock */ 127 uint8 lwWaitMode; /* lwlock mode being waited for */ 128 proclist_node lwWaitLink; /* position in LW lock wait list */ 129 130 /* Support for condition variables. */ 131 proclist_node cvWaitLink; /* position in CV wait list */ 132 133 /* Info about lock the process is currently waiting for, if any. */ 134 /* waitLock and waitProcLock are NULL if not currently waiting. */ 135 LOCK *waitLock; /* Lock object we're sleeping on ... */ 136 PROCLOCK *waitProcLock; /* Per-holder info for awaited lock */ 137 LOCKMODE waitLockMode; /* type of lock we're waiting for */ 138 LOCKMASK heldLocks; /* bitmask for lock types already held on this 139 * lock object by this backend */ 140 141 /* 142 * Info to allow us to wait for synchronous replication, if needed. 143 * waitLSN is InvalidXLogRecPtr if not waiting; set only by user backend. 144 * syncRepState must not be touched except by owning process or WALSender. 145 * syncRepLinks used only while holding SyncRepLock. 146 */ 147 XLogRecPtr waitLSN; /* waiting for this LSN or higher */ 148 int syncRepState; /* wait state for sync rep */ 149 SHM_QUEUE syncRepLinks; /* list link if process is in syncrep queue */ 150 151 /* 152 * All PROCLOCK objects for locks held or awaited by this backend are 153 * linked into one of these lists, according to the partition number of 154 * their lock. 155 */ 156 SHM_QUEUE myProcLocks[NUM_LOCK_PARTITIONS]; 157 158 struct XidCache subxids; /* cache for subtransaction XIDs */ 159 160 /* Support for group XID clearing. */ 161 /* true, if member of ProcArray group waiting for XID clear */ 162 bool procArrayGroupMember; 163 /* next ProcArray group member waiting for XID clear */ 164 pg_atomic_uint32 procArrayGroupNext; 165 166 /* 167 * latest transaction id among the transaction's main XID and 168 * subtransactions 169 */ 170 TransactionId procArrayGroupMemberXid; 171 172 uint32 wait_event_info; /* proc's wait information */ 173 174 /* Per-backend LWLock. Protects fields below (but not group fields). */ 175 LWLock backendLock; 176 177 /* Lock manager data, recording fast-path locks taken by this backend. */ 178 uint64 fpLockBits; /* lock modes held for each fast-path slot */ 179 Oid fpRelId[FP_LOCK_SLOTS_PER_BACKEND]; /* slots for rel oids */ 180 bool fpVXIDLock; /* are we holding a fast-path VXID lock? */ 181 LocalTransactionId fpLocalTransactionId; /* lxid for fast-path VXID 182 * lock */ 183 184 /* 185 * Support for lock groups. Use LockHashPartitionLockByProc on the group 186 * leader to get the LWLock protecting these fields. 187 */ 188 PGPROC *lockGroupLeader; /* lock group leader, if I'm a member */ 189 dlist_head lockGroupMembers; /* list of members, if I'm a leader */ 190 dlist_node lockGroupLink; /* my member link, if I'm a member */ 191 }; 192 193 /* NOTE: "typedef struct PGPROC PGPROC" appears in storage/lock.h. */ 194 195 196 extern PGDLLIMPORT PGPROC *MyProc; 197 extern PGDLLIMPORT struct PGXACT *MyPgXact; 198 199 /* 200 * Prior to PostgreSQL 9.2, the fields below were stored as part of the 201 * PGPROC. However, benchmarking revealed that packing these particular 202 * members into a separate array as tightly as possible sped up GetSnapshotData 203 * considerably on systems with many CPU cores, by reducing the number of 204 * cache lines needing to be fetched. Thus, think very carefully before adding 205 * anything else here. 206 */ 207 typedef struct PGXACT 208 { 209 TransactionId xid; /* id of top-level transaction currently being 210 * executed by this proc, if running and XID 211 * is assigned; else InvalidTransactionId */ 212 213 TransactionId xmin; /* minimal running XID as it was when we were 214 * starting our xact, excluding LAZY VACUUM: 215 * vacuum must not remove tuples deleted by 216 * xid >= xmin ! */ 217 218 uint8 vacuumFlags; /* vacuum-related flags, see above */ 219 bool overflowed; 220 bool delayChkpt; /* true if this proc delays checkpoint start; 221 * previously called InCommit */ 222 223 uint8 nxids; 224 } PGXACT; 225 226 /* 227 * There is one ProcGlobal struct for the whole database cluster. 228 */ 229 typedef struct PROC_HDR 230 { 231 /* Array of PGPROC structures (not including dummies for prepared txns) */ 232 PGPROC *allProcs; 233 /* Array of PGXACT structures (not including dummies for prepared txns) */ 234 PGXACT *allPgXact; 235 /* Length of allProcs array */ 236 uint32 allProcCount; 237 /* Head of list of free PGPROC structures */ 238 PGPROC *freeProcs; 239 /* Head of list of autovacuum's free PGPROC structures */ 240 PGPROC *autovacFreeProcs; 241 /* Head of list of bgworker free PGPROC structures */ 242 PGPROC *bgworkerFreeProcs; 243 /* First pgproc waiting for group XID clear */ 244 pg_atomic_uint32 procArrayGroupFirst; 245 /* WALWriter process's latch */ 246 Latch *walwriterLatch; 247 /* Checkpointer process's latch */ 248 Latch *checkpointerLatch; 249 /* Current shared estimate of appropriate spins_per_delay value */ 250 int spins_per_delay; 251 /* The proc of the Startup process, since not in ProcArray */ 252 PGPROC *startupProc; 253 int startupProcPid; 254 /* Buffer id of the buffer that Startup process waits for pin on, or -1 */ 255 int startupBufferPinWaitBufId; 256 } PROC_HDR; 257 258 extern PGDLLIMPORT PROC_HDR *ProcGlobal; 259 260 extern PGPROC *PreparedXactProcs; 261 262 /* Accessor for PGPROC given a pgprocno. */ 263 #define GetPGProcByNumber(n) (&ProcGlobal->allProcs[(n)]) 264 265 /* 266 * We set aside some extra PGPROC structures for auxiliary processes, 267 * ie things that aren't full-fledged backends but need shmem access. 268 * 269 * Background writer, checkpointer and WAL writer run during normal operation. 270 * Startup process and WAL receiver also consume 2 slots, but WAL writer is 271 * launched only after startup has exited, so we only need 4 slots. 272 */ 273 #define NUM_AUXILIARY_PROCS 4 274 275 /* configurable options */ 276 extern PGDLLIMPORT int DeadlockTimeout; 277 extern PGDLLIMPORT int StatementTimeout; 278 extern PGDLLIMPORT int LockTimeout; 279 extern PGDLLIMPORT int IdleInTransactionSessionTimeout; 280 extern bool log_lock_waits; 281 282 283 /* 284 * Function Prototypes 285 */ 286 extern int ProcGlobalSemas(void); 287 extern Size ProcGlobalShmemSize(void); 288 extern void InitProcGlobal(void); 289 extern void InitProcess(void); 290 extern void InitProcessPhase2(void); 291 extern void InitAuxiliaryProcess(void); 292 293 extern void PublishStartupProcessInformation(void); 294 extern void SetStartupBufferPinWaitBufId(int bufid); 295 extern int GetStartupBufferPinWaitBufId(void); 296 297 extern bool HaveNFreeProcs(int n); 298 extern void ProcReleaseLocks(bool isCommit); 299 300 extern void ProcQueueInit(PROC_QUEUE *queue); 301 extern int ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable); 302 extern PGPROC *ProcWakeup(PGPROC *proc, int waitStatus); 303 extern void ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock); 304 extern void CheckDeadLockAlert(void); 305 extern bool IsWaitingForLock(void); 306 extern void LockErrorCleanup(void); 307 308 extern void ProcWaitForSignal(uint32 wait_event_info); 309 extern void ProcSendSignal(int pid); 310 311 extern PGPROC *AuxiliaryPidGetProc(int pid); 312 313 extern void BecomeLockGroupLeader(void); 314 extern bool BecomeLockGroupMember(PGPROC *leader, int pid); 315 316 #endif /* PROC_H */ 317