/
githubmirror
/
postgres
Обзор
Документация
Войти
/
githubmirror
/
postgres
Код
Запросы
0
Пакеты
0
Релизы
0
Аналитика
Безопасность
master
src/include/storage/proc.h
587 строк
23 KB
Heikki Linnakangas
Fix advertising autovacuum launcher's ProcNumber
09 июл 2026, 15:14
09 июл 2026, 15:14
dff789e
Код
Авторство
О чём код?
/*------------------------------------------------------------------------- * * proc.h * per-process shared memory data structures * * * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * src/include/storage/proc.h * *------------------------------------------------------------------------- */ #ifndef _PROC_H_ #define _PROC_H_ #include "access/xlogdefs.h" #include "lib/ilist.h" #include "miscadmin.h" #include "storage/latch.h" #include "storage/lock.h" #include "storage/pg_sema.h" #include "storage/proclist_types.h" #include "storage/procnumber.h" #include "storage/spin.h" /* Avoid including clog.h here */ typedef int XidStatus; /* * Each backend advertises up to PGPROC_MAX_CACHED_SUBXIDS TransactionIds * for non-aborted subtransactions of its current top transaction. These * have to be treated as running XIDs by other backends. * * We also keep track of whether the cache overflowed (ie, the transaction has * generated at least one subtransaction that didn't fit in the cache). * If none of the caches have overflowed, we can assume that an XID that's not * listed anywhere in the PGPROC array is not a running transaction. Else we * have to look at pg_subtrans. * * See src/test/isolation/specs/subxid-overflow.spec if you change this. */ #define PGPROC_MAX_CACHED_SUBXIDS 64 /* XXX guessed-at value */ typedef struct XidCacheStatus { /* number of cached subxids, never more than PGPROC_MAX_CACHED_SUBXIDS */ uint8 count; /* has PGPROC->subxids overflowed */ bool overflowed; } XidCacheStatus; struct XidCache { TransactionId xids[PGPROC_MAX_CACHED_SUBXIDS]; }; /* * Flags for PGPROC->statusFlags and PROC_HDR->statusFlags[] */ #define PROC_IS_AUTOVACUUM 0x01 /* is it an autovac worker? */ #define PROC_IN_VACUUM 0x02 /* currently running lazy vacuum */ #define PROC_IN_SAFE_IC 0x04 /* currently running CREATE INDEX * CONCURRENTLY or REINDEX * CONCURRENTLY on non-expressional, * non-partial index */ #define PROC_VACUUM_FOR_WRAPAROUND 0x08 /* set by autovac only */ #define PROC_IN_LOGICAL_DECODING 0x10 /* currently doing logical * decoding outside xact */ #define PROC_AFFECTS_ALL_HORIZONS 0x20 /* this proc's xmin must be * included in vacuum horizons * in all databases */ /* flags reset at EOXact */ #define PROC_VACUUM_STATE_MASK \ (PROC_IN_VACUUM | PROC_IN_SAFE_IC | PROC_VACUUM_FOR_WRAPAROUND) /* * Xmin-related flags. Make sure any flags that affect how the process' Xmin * value is interpreted by VACUUM are included here. */ #define PROC_XMIN_FLAGS (PROC_IN_VACUUM | PROC_IN_SAFE_IC) /* * We allow a limited number of "weak" relation locks (AccessShareLock, * RowShareLock, RowExclusiveLock) to be recorded in the PGPROC structure * (or rather in shared memory referenced from PGPROC) rather than the main * lock table. This eases contention on the lock manager LWLocks. See * storage/lmgr/README for additional details. */ extern PGDLLIMPORT int FastPathLockGroupsPerBackend; /* * Define the maximum number of fast-path locking groups per backend. * This must be a power-of-two value. The actual number of fast-path * lock groups is calculated in InitializeFastPathLocks() based on * max_locks_per_transaction. 1024 is an arbitrary upper limit (matching * max_locks_per_transaction = 16k). Values over 1024 are unlikely to be * beneficial as there are bottlenecks we'll hit way before that. */ #define FP_LOCK_GROUPS_PER_BACKEND_MAX 1024 #define FP_LOCK_SLOTS_PER_GROUP 16 /* don't change */ #define FastPathLockSlotsPerBackend() \ (FP_LOCK_SLOTS_PER_GROUP * FastPathLockGroupsPerBackend) /* * Flags for PGPROC.delayChkptFlags * * These flags can be used to delay the start or completion of a checkpoint * for short periods. A flag is in effect if the corresponding bit is set in * the PGPROC of any backend. * * For our purposes here, a checkpoint has three phases: (1) determine the * location to which the redo pointer will be moved, (2) write all the * data durably to disk, and (3) WAL-log the checkpoint. * * Setting DELAY_CHKPT_START prevents the system from moving from phase 1 * to phase 2. This is useful when we are performing a WAL-logged modification * of data that will be flushed to disk in phase 2. By setting this flag * before writing WAL and clearing it after we've both written WAL and * performed the corresponding modification, we ensure that if the WAL record * is inserted prior to the new redo point, the corresponding data changes will * also be flushed to disk before the checkpoint can complete. (In the * extremely common case where the data being modified is in shared buffers * and we acquire an exclusive content lock and MarkBufferDirty() on the * relevant buffers before writing WAL, this mechanism is not needed, because * phase 2 will block until we release the content lock and then flush the * modified data to disk. See transam/README and SyncOneBuffer().) * * Setting DELAY_CHKPT_COMPLETE prevents the system from moving from phase 2 * to phase 3. This is useful if we are performing a WAL-logged operation that * might invalidate buffers, such as relation truncation. In this case, we need * to ensure that any buffers which were invalidated and thus not flushed by * the checkpoint are actually destroyed on disk. Replay can cope with a file * or block that doesn't exist, but not with a block that has the wrong * contents. * * Setting DELAY_CHKPT_IN_COMMIT is similar to setting DELAY_CHKPT_START, but * it explicitly indicates that the reason for delaying the checkpoint is due * to a transaction being within a critical commit section. We need this new * flag to ensure all the transactions that have acquired commit timestamp are * finished before we allow the logical replication client to advance its xid * which is used to hold back dead rows for conflict detection. */ #define DELAY_CHKPT_START (1<<0) #define DELAY_CHKPT_COMPLETE (1<<1) #define DELAY_CHKPT_IN_COMMIT (DELAY_CHKPT_START | 1<<2) typedef enum { PROC_WAIT_STATUS_OK, PROC_WAIT_STATUS_WAITING, PROC_WAIT_STATUS_ERROR, } ProcWaitStatus; /* * Each backend has a PGPROC struct in shared memory. There is also a list of * currently-unused PGPROC structs that will be reallocated to new backends. * * Note: twophase.c also sets up a dummy PGPROC struct for each currently * prepared transaction. These PGPROCs appear in the ProcArray data structure * so that the prepared transactions appear to be still running and are * correctly shown as holding locks. A prepared transaction PGPROC can be * distinguished from a real one at need by the fact that it has pid == 0. * The semaphore and lock-activity fields in a prepared-xact PGPROC are unused, * but its myProcLocks[] lists are valid. * * We allow many fields of this struct to be accessed without locks, such as * delayChkptFlags and backendType. However, keep in mind that writing * mirrored ones (see below) requires holding ProcArrayLock or XidGenLock in * at least shared mode, so that pgxactoff does not change concurrently. * * Mirrored fields: * * Some fields in PGPROC (see "mirrored in ..." comment) are mirrored into an * element of more densely packed ProcGlobal arrays. These arrays are indexed * by PGPROC->pgxactoff. Both copies need to be maintained coherently. * * NB: The pgxactoff indexed value can *never* be accessed without holding * locks. * * See PROC_HDR for details. */ typedef struct PGPROC { /* * Align the struct at cache line boundaries. This is just for * performance, to avoid false sharing. */ alignas(PG_CACHE_LINE_SIZE) dlist_head *procgloballist; /* procglobal list that owns this PGPROC */ dlist_node freeProcsLink; /* link in procgloballist, when in recycled * state */ /************************************************************************ * Backend identity ************************************************************************/ /* * These fields that don't change after backend startup, or only very * rarely */ int pid; /* Backend's process ID; 0 if prepared xact */ BackendType backendType; /* what kind of process is this? */ /* These fields are zero while a backend is still starting up: */ Oid databaseId; /* OID of database this backend is using */ Oid roleId; /* OID of role using this backend */ Oid tempNamespaceId; /* OID of temp schema this backend is * using */ int pgxactoff; /* offset into various ProcGlobal->arrays with * data mirrored from this PGPROC */ uint8 statusFlags; /* this backend's status flags, see PROC_* * above. mirrored in * ProcGlobal->statusFlags[pgxactoff] */ /************************************************************************ * Transactions and snapshots ************************************************************************/ /* * Currently running top-level transaction's virtual xid. Together these * form a VirtualTransactionId, but we don't use that struct because this * is not atomically assignable as whole, and we want to enforce code to * consider both parts separately. See comments at VirtualTransactionId. */ struct { ProcNumber procNumber; /* For regular backends, equal to * GetNumberFromPGProc(proc). For prepared * xacts, ID of the original backend that * processed the transaction. For unused * PGPROC entries, INVALID_PROC_NUMBER. */ LocalTransactionId lxid; /* local id of top-level transaction * currently * being executed by this * proc, if running; else * InvalidLocalTransactionId */ } vxid; TransactionId xid; /* id of top-level transaction currently being * executed by this proc, if running and XID * is assigned; else InvalidTransactionId. * mirrored in ProcGlobal->xids[pgxactoff] */ TransactionId xmin; /* minimal running XID as it was when we were * starting our xact, excluding LAZY VACUUM: * vacuum must not remove tuples deleted by * xid >= xmin ! */ XidCacheStatus subxidStatus; /* mirrored with * ProcGlobal->subxidStates[i] */ struct XidCache subxids; /* cache for subtransaction XIDs */ /************************************************************************ * Inter-process signaling ************************************************************************/ Latch procLatch; /* generic latch for process */ PGSemaphore sem; /* ONE semaphore to sleep on */ int delayChkptFlags; /* for DELAY_CHKPT_* flags */ /* * While in hot standby mode, shows that a conflict signal has been sent * for the current transaction. Set/cleared while holding ProcArrayLock, * though not required. Accessed without lock, if needed. * * This is a bitmask; each bit corresponds to a RecoveryConflictReason * enum value. */ pg_atomic_uint32 pendingRecoveryConflicts; /************************************************************************ * LWLock waiting ************************************************************************/ /* * Info about LWLock the process is currently waiting for, if any. * * This is currently used both for lwlocks and buffer content locks, which * is acceptable, although not pretty, because a backend can't wait for * both types of locks at the same time. */ uint8 lwWaiting; /* see LWLockWaitState */ uint8 lwWaitMode; /* lwlock mode being waited for */ proclist_node lwWaitLink; /* position in LW lock wait list */ /* Support for condition variables. */ proclist_node cvWaitLink; /* position in CV wait list */ /************************************************************************ * Lock manager data ************************************************************************/ /* * Support for lock groups. Use LockHashPartitionLockByProc on the group * leader to get the LWLock protecting these fields. */ PGPROC *lockGroupLeader; /* lock group leader, if I'm a member */ dlist_head lockGroupMembers; /* list of members, if I'm a leader */ dlist_node lockGroupLink; /* my member link, if I'm a member */ /* Info about lock the process is currently waiting for, if any. */ /* waitLock and waitProcLock are NULL if not currently waiting. */ LOCK *waitLock; /* Lock object we're sleeping on ... */ dlist_node waitLink; /* position in waitLock->waitProcs queue */ PROCLOCK *waitProcLock; /* Per-holder info for awaited lock */ LOCKMODE waitLockMode; /* type of lock we're waiting for */ LOCKMASK heldLocks; /* bitmask for lock types already held on this * lock object by this backend */ pg_atomic_uint64 waitStart; /* time at which wait for lock acquisition * started */ ProcWaitStatus waitStatus; /* * All PROCLOCK objects for locks held or awaited by this backend are * linked into one of these lists, according to the partition number of * their lock. */ dlist_head myProcLocks[NUM_LOCK_PARTITIONS]; /*-- recording fast-path locks taken by this backend. --*/ LWLock fpInfoLock; /* protects per-backend fast-path state */ uint64 *fpLockBits; /* lock modes held for each fast-path slot */ Oid *fpRelId; /* slots for rel oids */ bool fpVXIDLock; /* are we holding a fast-path VXID lock? */ LocalTransactionId fpLocalTransactionId; /* lxid for fast-path VXID * lock */ /************************************************************************ * Synchronous replication waiting ************************************************************************/ /* * Info to allow us to wait for synchronous replication, if needed. * waitLSN is InvalidXLogRecPtr if not waiting; set only by user backend. * syncRepState must not be touched except by owning process or WALSender. * syncRepLinks used only while holding SyncRepLock. */ XLogRecPtr waitLSN; /* waiting for this LSN or higher */ int syncRepState; /* wait state for sync rep */ dlist_node syncRepLinks; /* list link if process is in syncrep queue */ /************************************************************************ * Support for group XID clearing ************************************************************************/ /* true, if member of ProcArray group waiting for XID clear */ bool procArrayGroupMember; /* next ProcArray group member waiting for XID clear */ pg_atomic_uint32 procArrayGroupNext; /* * latest transaction id among the transaction's main XID and * subtransactions */ TransactionId procArrayGroupMemberXid; /************************************************************************ * Support for group transaction status update ************************************************************************/ bool clogGroupMember; /* true, if member of clog group */ pg_atomic_uint32 clogGroupNext; /* next clog group member */ TransactionId clogGroupMemberXid; /* transaction id of clog group member */ XidStatus clogGroupMemberXidStatus; /* transaction status of clog * group member */ int64 clogGroupMemberPage; /* clog page corresponding to * transaction id of clog group member */ XLogRecPtr clogGroupMemberLsn; /* WAL location of commit record for clog * group member */ /************************************************************************ * Status reporting ************************************************************************/ uint32 wait_event_info; /* proc's wait information */ } PGPROC; extern PGDLLIMPORT PGPROC *MyProc; /* * There is one ProcGlobal struct for the whole database cluster. * * Adding/Removing an entry into the procarray requires holding *both* * ProcArrayLock and XidGenLock in exclusive mode (in that order). Both are * needed because the dense arrays (see below) are accessed from * GetNewTransactionId() and GetSnapshotData(), and we don't want to add * further contention by both using the same lock. Adding/Removing a procarray * entry is much less frequent. * * Some fields in PGPROC are mirrored into more densely packed arrays (e.g. * xids), with one entry for each backend. These arrays only contain entries * for PGPROCs that have been added to the shared array with ProcArrayAdd() * (in contrast to PGPROC array which has unused PGPROCs interspersed). * * The dense arrays are indexed by PGPROC->pgxactoff. Any concurrent * ProcArrayAdd() / ProcArrayRemove() can lead to pgxactoff of a procarray * member to change. Therefore it is only safe to use PGPROC->pgxactoff to * access the dense array while holding either ProcArrayLock or XidGenLock. * * As long as a PGPROC is in the procarray, the mirrored values need to be * maintained in both places in a coherent manner. * * The denser separate arrays are beneficial for three main reasons: First, to * allow for as tight loops accessing the data as possible. Second, to prevent * updates of frequently changing data (e.g. xmin) from invalidating * cachelines also containing less frequently changing data (e.g. xid, * statusFlags). Third to condense frequently accessed data into as few * cachelines as possible. * * There are two main reasons to have the data mirrored between these dense * arrays and PGPROC. First, as explained above, a PGPROC's array entries can * only be accessed with either ProcArrayLock or XidGenLock held, whereas the * PGPROC entries do not require that (obviously there may still be locking * requirements around the individual field, separate from the concerns * here). That is particularly important for a backend to efficiently checks * it own values, which it often can safely do without locking. Second, the * PGPROC fields allow to avoid unnecessary accesses and modification to the * dense arrays. A backend's own PGPROC is more likely to be in a local cache, * whereas the cachelines for the dense array will be modified by other * backends (often removing it from the cache for other cores/sockets). At * commit/abort time a check of the PGPROC value can avoid accessing/dirtying * the corresponding array value. * * Basically it makes sense to access the PGPROC variable when checking a * single backend's data, especially when already looking at the PGPROC for * other reasons already. It makes sense to look at the "dense" arrays if we * need to look at many / most entries, because we then benefit from the * reduced indirection and better cross-process cache-ability. * * When entering a PGPROC for 2PC transactions with ProcArrayAdd(), the data * in the dense arrays is initialized from the PGPROC while it already holds * ProcArrayLock. */ typedef struct PROC_HDR { /* Array of PGPROC structures (not including dummies for prepared txns) */ PGPROC *allProcs; /* Array mirroring PGPROC.xid for each PGPROC currently in the procarray */ TransactionId *xids; /* * Array mirroring PGPROC.subxidStatus for each PGPROC currently in the * procarray. */ XidCacheStatus *subxidStates; /* * Array mirroring PGPROC.statusFlags for each PGPROC currently in the * procarray. */ uint8 *statusFlags; /* Length of allProcs array */ uint32 allProcCount; /* * This spinlock protects the below freelists of PGPROC structures. We * cannot use an LWLock because the LWLock manager depends on already * having a PGPROC and a wait semaphore! But these structures are touched * relatively infrequently (only at backend startup or shutdown) and not * for very long, so a spinlock is okay. */ slock_t freeProcsLock; /* Head of list of free PGPROC structures */ dlist_head freeProcs; /* Head of list of autovacuum & special worker free PGPROC structures */ dlist_head autovacFreeProcs; /* Head of list of bgworker free PGPROC structures */ dlist_head bgworkerFreeProcs; /* Head of list of walsender free PGPROC structures */ dlist_head walsenderFreeProcs; /* First pgproc waiting for group XID clear */ pg_atomic_uint32 procArrayGroupFirst; /* First pgproc waiting for group transaction status update */ pg_atomic_uint32 clogGroupFirst; /* * Current proc numbers of some auxiliary processes. There can be only one * of each of these running at a time. */ pg_atomic_uint32 walwriterProc; pg_atomic_uint32 checkpointerProc; /* avlauncher is not an aux process, but it is advertised the same way */ pg_atomic_uint32 avLauncherProc; /* Current shared estimate of appropriate spins_per_delay value */ int spins_per_delay; /* Buffer id of the buffer that Startup process waits for pin on, or -1 */ int startupBufferPinWaitBufId; } PROC_HDR; extern PGDLLIMPORT PROC_HDR *ProcGlobal; extern PGDLLIMPORT PGPROC *PreparedXactProcs; /* * Accessors for getting PGPROC given a ProcNumber and vice versa. */ #define GetPGProcByNumber(n) (&ProcGlobal->allProcs[(n)]) #define GetNumberFromPGProc(proc) ((proc) - &ProcGlobal->allProcs[0]) /* * We set aside some extra PGPROC structures for "special worker" processes, * which are full-fledged backends (they can run transactions) * but are unique animals that there's never more than one of. * Currently there are two such processes: the autovacuum launcher * and the slotsync worker. */ #define NUM_SPECIAL_WORKER_PROCS 2 /* * We set aside some extra PGPROC structures for auxiliary processes, * ie things that aren't full-fledged backends (they cannot run transactions * or take heavyweight locks) but need shmem access. * * Background writer, checkpointer, WAL writer, WAL summarizer, and archiver * run during normal operation. Startup process and WAL receiver also consume * 2 slots, but WAL writer is launched only after startup has exited, so we * only need 6 slots. */ #define MAX_IO_WORKERS 32 #define NUM_AUXILIARY_PROCS (6 + MAX_IO_WORKERS) #define FIRST_PREPARED_XACT_PROC_NUMBER (MaxBackends + NUM_AUXILIARY_PROCS) /* configurable options */ extern PGDLLIMPORT int DeadlockTimeout; extern PGDLLIMPORT int StatementTimeout; extern PGDLLIMPORT int LockTimeout; extern PGDLLIMPORT int IdleInTransactionSessionTimeout; extern PGDLLIMPORT int TransactionTimeout; extern PGDLLIMPORT int IdleSessionTimeout; extern PGDLLIMPORT bool log_lock_waits; #ifdef EXEC_BACKEND extern PGDLLIMPORT PGPROC *AuxiliaryProcs; #endif /* * Function Prototypes */ extern int ProcGlobalSemas(void); extern void InitProcess(void); extern void InitProcessPhase2(void); extern void InitAuxiliaryProcess(void); extern void SetStartupBufferPinWaitBufId(int bufid); extern int GetStartupBufferPinWaitBufId(void); extern bool HaveNFreeProcs(int n, int *nfree); extern void ProcReleaseLocks(bool isCommit); extern ProcWaitStatus JoinWaitQueue(LOCALLOCK *locallock, LockMethod lockMethodTable, bool dontWait); extern ProcWaitStatus ProcSleep(LOCALLOCK *locallock); extern void ProcWakeup(PGPROC *proc, ProcWaitStatus waitStatus); extern void ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock); extern void CheckDeadLockAlert(void); extern void LockErrorCleanup(void); extern void GetLockHoldersAndWaiters(LOCALLOCK *locallock, StringInfo lock_holders_sbuf, StringInfo lock_waiters_sbuf, int *lockHoldersNum); extern void ProcWaitForSignal(uint32 wait_event_info); extern void ProcSendSignal(ProcNumber procNumber); extern PGPROC *AuxiliaryPidGetProc(int pid); extern void BecomeLockGroupLeader(void); extern bool BecomeLockGroupMember(PGPROC *leader, int pid); #endif /* _PROC_H_ */