1 /*-------------------------------------------------------------------------
4 * per-process shared memory data structures
7 * Portions Copyright (c) 1996-2011, 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/xlog.h"
18 #include "replication/syncrep.h"
19 #include "storage/latch.h"
20 #include "storage/lock.h"
21 #include "storage/pg_sema.h"
22 #include "utils/timestamp.h"
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.
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.
35 #define PGPROC_MAX_CACHED_SUBXIDS 64 /* XXX guessed-at value */
41 TransactionId xids[PGPROC_MAX_CACHED_SUBXIDS];
44 /* Flags for PGPROC->vacuumFlags */
45 #define PROC_IS_AUTOVACUUM 0x01 /* is it an autovac worker? */
46 #define PROC_IN_VACUUM 0x02 /* currently running lazy vacuum */
47 #define PROC_IN_ANALYZE 0x04 /* currently running analyze */
48 #define PROC_VACUUM_FOR_WRAPAROUND 0x08 /* set by autovac only */
50 /* flags reset at EOXact */
51 #define PROC_VACUUM_STATE_MASK (0x0E)
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 * Each backend has a PGPROC struct in shared memory. There is also a list of
63 * currently-unused PGPROC structs that will be reallocated to new backends.
65 * links: list link for any list the PGPROC is in. When waiting for a lock,
66 * the PGPROC is linked into that lock's waitProcs queue. A recycled PGPROC
67 * is linked into ProcGlobal's freeProcs list.
69 * Note: twophase.c also sets up a dummy PGPROC struct for each currently
70 * prepared transaction. These PGPROCs appear in the ProcArray data structure
71 * so that the prepared transactions appear to be still running and are
72 * correctly shown as holding locks. A prepared transaction PGPROC can be
73 * distinguished from a real one at need by the fact that it has pid == 0.
74 * The semaphore and lock-activity fields in a prepared-xact PGPROC are unused,
75 * but its myProcLocks[] lists are valid.
79 /* proc->links MUST BE FIRST IN STRUCT (see ProcSleep,ProcWakeup,etc) */
80 SHM_QUEUE links; /* list link if process is in a list */
82 PGSemaphoreData sem; /* ONE semaphore to sleep on */
83 int waitStatus; /* STATUS_WAITING, STATUS_OK or STATUS_ERROR */
85 LocalTransactionId lxid; /* local id of top-level transaction currently
86 * being executed by this proc, if running;
87 * else InvalidLocalTransactionId */
89 TransactionId xid; /* id of top-level transaction currently being
90 * executed by this proc, if running and XID
91 * is assigned; else InvalidTransactionId */
93 TransactionId xmin; /* minimal running XID as it was when we were
94 * starting our xact, excluding LAZY VACUUM:
95 * vacuum must not remove tuples deleted by
98 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 */
105 bool inCommit; /* true if within commit critical section */
107 uint8 vacuumFlags; /* vacuum-related flags, see above */
110 * While in hot standby mode, shows that a conflict signal has been sent
111 * for the current transaction. Set/cleared while holding ProcArrayLock,
112 * though not required. Accessed without lock, if needed.
114 bool recoveryConflictPending;
116 /* Info about LWLock the process is currently waiting for, if any. */
117 bool lwWaiting; /* true if waiting for an LW lock */
118 bool lwExclusive; /* true if waiting for exclusive access */
119 struct PGPROC *lwWaitLink; /* next waiter for same LW lock */
121 /* Info about lock the process is currently waiting for, if any. */
122 /* waitLock and waitProcLock are NULL if not currently waiting. */
123 LOCK *waitLock; /* Lock object we're sleeping on ... */
124 PROCLOCK *waitProcLock; /* Per-holder info for awaited lock */
125 LOCKMODE waitLockMode; /* type of lock we're waiting for */
126 LOCKMASK heldLocks; /* bitmask for lock types already held on this
127 * lock object by this backend */
130 * Info to allow us to wait for synchronous replication, if needed.
131 * waitLSN is InvalidXLogRecPtr if not waiting; set only by user backend.
132 * syncRepState must not be touched except by owning process or WALSender.
133 * syncRepLinks used only while holding SyncRepLock.
135 Latch waitLatch; /* allow us to wait for sync rep */
136 XLogRecPtr waitLSN; /* waiting for this LSN or higher */
137 int syncRepState; /* wait state for sync rep */
138 SHM_QUEUE syncRepLinks; /* list link if process is in syncrep queue */
141 * All PROCLOCK objects for locks held or awaited by this backend are
142 * linked into one of these lists, according to the partition number of
145 SHM_QUEUE myProcLocks[NUM_LOCK_PARTITIONS];
147 struct XidCache subxids; /* cache for subtransaction XIDs */
149 /* Per-backend LWLock. Protects fields below. */
150 LWLockId 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 */
157 /* NOTE: "typedef struct PGPROC PGPROC" appears in storage/lock.h. */
160 extern PGDLLIMPORT PGPROC *MyProc;
164 * There is one ProcGlobal struct for the whole database cluster.
166 typedef struct PROC_HDR
168 /* Array of PGPROC structures (not including dummies for prepared txns) */
170 /* Length of allProcs array */
172 /* Head of list of free PGPROC structures */
174 /* Head of list of autovacuum's free PGPROC structures */
175 PGPROC *autovacFreeProcs;
176 /* Current shared estimate of appropriate spins_per_delay value */
178 /* The proc of the Startup process, since not in ProcArray */
181 /* Buffer id of the buffer that Startup process waits for pin on */
182 int startupBufferPinWaitBufId;
185 extern PROC_HDR *ProcGlobal;
188 * We set aside some extra PGPROC structures for auxiliary processes,
189 * ie things that aren't full-fledged backends but need shmem access.
191 * Background writer and WAL writer run during normal operation. Startup
192 * process and WAL receiver also consume 2 slots, but WAL writer is
193 * launched only after startup has exited, so we only need 3 slots.
195 #define NUM_AUXILIARY_PROCS 3
198 /* configurable options */
199 extern int DeadlockTimeout;
200 extern int StatementTimeout;
201 extern bool log_lock_waits;
203 extern volatile bool cancel_from_timeout;
207 * Function Prototypes
209 extern int ProcGlobalSemas(void);
210 extern Size ProcGlobalShmemSize(void);
211 extern void InitProcGlobal(void);
212 extern void InitProcess(void);
213 extern void InitProcessPhase2(void);
214 extern void InitAuxiliaryProcess(void);
216 extern void PublishStartupProcessInformation(void);
217 extern void SetStartupBufferPinWaitBufId(int bufid);
218 extern int GetStartupBufferPinWaitBufId(void);
220 extern bool HaveNFreeProcs(int n);
221 extern void ProcReleaseLocks(bool isCommit);
223 extern void ProcQueueInit(PROC_QUEUE *queue);
224 extern int ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable);
225 extern PGPROC *ProcWakeup(PGPROC *proc, int waitStatus);
226 extern void ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock);
227 extern bool IsWaitingForLock(void);
228 extern void LockWaitCancel(void);
230 extern void ProcWaitForSignal(void);
231 extern void ProcSendSignal(int pid);
233 extern bool enable_sig_alarm(int delayms, bool is_statement_timeout);
234 extern bool disable_sig_alarm(bool is_statement_timeout);
235 extern void handle_sig_alarm(SIGNAL_ARGS);
237 extern bool enable_standby_sig_alarm(TimestampTz now,
238 TimestampTz fin_time, bool deadlock_only);
239 extern bool disable_standby_sig_alarm(void);
240 extern void handle_standby_sig_alarm(SIGNAL_ARGS);