PostgreSQL Source Code  git master
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros
proc.h
Go to the documentation of this file.
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 {
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  */
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  */
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 */
163  /* next ProcArray group member waiting for XID clear */
165 
166  /*
167  * latest transaction id among the transaction's main XID and
168  * subtransactions
169  */
171 
172  uint32 wait_event_info; /* proc's wait information */
173 
174  /* Per-backend LWLock. Protects fields below (but not group fields). */
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 */
220  bool delayChkpt; /* true if this proc delays checkpoint start;
221  * previously called InCommit */
222 
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) */
233  /* Array of PGXACT structures (not including dummies for prepared txns) */
235  /* Length of allProcs array */
237  /* Head of list of free PGPROC structures */
239  /* Head of list of autovacuum's free PGPROC structures */
241  /* Head of list of bgworker free PGPROC structures */
243  /* First pgproc waiting for group XID clear */
245  /* WALWriter process's latch */
247  /* Checkpointer process's latch */
249  /* Current shared estimate of appropriate spins_per_delay value */
251  /* The proc of the Startup process, since not in ProcArray */
254  /* Buffer id of the buffer that Startup process waits for pin on, or -1 */
256 } PROC_HDR;
257 
258 extern 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 int DeadlockTimeout;
277 extern int StatementTimeout;
278 extern int LockTimeout;
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 */
PGDLLIMPORT PGPROC * MyProc
Definition: proc.c:67
PROC_HDR * ProcGlobal
Definition: proc.c:80
bool procArrayGroupMember
Definition: proc.h:162
Definition: lwlock.h:32
bool log_lock_waits
Definition: proc.c:64
BackendId backendId
Definition: proc.h:112
uint32 TransactionId
Definition: c.h:397
uint32 wait_event_info
Definition: proc.h:172
Definition: proc.h:207
int LOCKMODE
Definition: lockdefs.h:26
dlist_head lockGroupMembers
Definition: proc.h:189
TransactionId xmin
Definition: proc.h:213
PGXACT * allPgXact
Definition: proc.h:234
TransactionId xid
Definition: proc.h:209
SHM_QUEUE links
Definition: proc.h:97
LOCKMODE waitLockMode
Definition: proc.h:137
int DeadlockTimeout
Definition: proc.c:60
bool lwWaiting
Definition: proc.h:126
unsigned char uint8
Definition: c.h:266
PGPROC * bgworkerFreeProcs
Definition: proc.h:242
int GetStartupBufferPinWaitBufId(void)
Definition: proc.c:623
int ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
Definition: proc.c:1028
Oid roleId
Definition: proc.h:114
void LockErrorCleanup(void)
Definition: proc.c:677
uint8 lwWaitMode
Definition: proc.h:127
bool fpVXIDLock
Definition: proc.h:180
unsigned int Oid
Definition: postgres_ext.h:31
PGPROC * autovacFreeProcs
Definition: proc.h:240
void ProcSendSignal(int pid)
Definition: proc.c:1777
PGPROC * ProcWakeup(PGPROC *proc, int waitStatus)
Definition: proc.c:1559
void SetStartupBufferPinWaitBufId(int bufid)
Definition: proc.c:611
Latch procLatch
Definition: proc.h:103
void InitProcessPhase2(void)
Definition: proc.c:447
#define PGDLLIMPORT
Definition: c.h:1063
PGPROC * AuxiliaryPidGetProc(int pid)
Definition: proc.c:951
uint8 vacuumFlags
Definition: proc.h:218
bool isBackgroundWorker
Definition: proc.h:116
dlist_node lockGroupLink
Definition: proc.h:190
Latch * walwriterLatch
Definition: proc.h:246
int spins_per_delay
Definition: proc.h:250
bool BecomeLockGroupMember(PGPROC *leader, int pid)
Definition: proc.c:1845
int ProcGlobalSemas(void)
Definition: proc.c:128
int IdleInTransactionSessionTimeout
Definition: proc.c:63
int LockTimeout
Definition: proc.c:62
proclist_node lwWaitLink
Definition: proc.h:128
void ProcWaitForSignal(uint32 wait_event_info)
Definition: proc.c:1766
PROCLOCK * waitProcLock
Definition: proc.h:136
Definition: latch.h:110
#define FP_LOCK_SLOTS_PER_BACKEND
Definition: proc.h:70
bool recoveryConflictPending
Definition: proc.h:123
uint8 nxids
Definition: proc.h:223
int StatementTimeout
Definition: proc.c:61
bool HaveNFreeProcs(int n)
Definition: proc.c:637
Oid databaseId
Definition: proc.h:113
unsigned int uint32
Definition: c.h:268
PGPROC ** procgloballist
Definition: proc.h:98
Definition: lock.h:284
uint32 LocalTransactionId
Definition: c.h:399
LOCK * waitLock
Definition: proc.h:135
void ProcReleaseLocks(bool isCommit)
Definition: proc.c:753
struct XidCache subxids
Definition: proc.h:158
bool delayChkpt
Definition: proc.h:220
void BecomeLockGroupLeader(void)
Definition: proc.c:1815
void ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock)
Definition: proc.c:1595
pg_atomic_uint32 procArrayGroupNext
Definition: proc.h:164
Definition: proc.h:229
PGDLLIMPORT struct PGXACT * MyPgXact
Definition: proc.c:68
PGPROC * PreparedXactProcs
Definition: proc.c:82
int startupProcPid
Definition: proc.h:253
uint64 fpLockBits
Definition: proc.h:178
int BackendId
Definition: backendid.h:21
bool overflowed
Definition: proc.h:219
int waitStatus
Definition: proc.h:101
#define PGPROC_MAX_CACHED_SUBXIDS
Definition: proc.h:35
Latch * checkpointerLatch
Definition: proc.h:248
TransactionId xids[PGPROC_MAX_CACHED_SUBXIDS]
Definition: proc.h:39
Oid fpRelId[FP_LOCK_SLOTS_PER_BACKEND]
Definition: proc.h:179
void InitProcGlobal(void)
Definition: proc.c:162
void ProcQueueInit(PROC_QUEUE *queue)
Definition: proc.c:1004
uint64 XLogRecPtr
Definition: xlogdefs.h:21
void CheckDeadLockAlert(void)
Definition: proc.c:1743
PGPROC * freeProcs
Definition: proc.h:238
void InitAuxiliaryProcess(void)
Definition: proc.c:482
LWLock backendLock
Definition: proc.h:175
size_t Size
Definition: c.h:356
SHM_QUEUE syncRepLinks
Definition: proc.h:149
uint32 allProcCount
Definition: proc.h:236
int LOCKMASK
Definition: lockdefs.h:25
proclist_node cvWaitLink
Definition: proc.h:131
void PublishStartupProcessInformation(void)
Definition: proc.c:593
Definition: lock.h:344
int pgprocno
Definition: proc.h:109
pg_atomic_uint32 procArrayGroupFirst
Definition: proc.h:244
bool IsWaitingForLock(void)
Definition: proc.c:660
int startupBufferPinWaitBufId
Definition: proc.h:255
void InitProcess(void)
Definition: proc.c:287
PGPROC * allProcs
Definition: proc.h:232
SHM_QUEUE myProcLocks[NUM_LOCK_PARTITIONS]
Definition: proc.h:156
struct PROC_HDR PROC_HDR
PGPROC * startupProc
Definition: proc.h:252
PGSemaphore sem
Definition: proc.h:100
int syncRepState
Definition: proc.h:148
Definition: proc.h:94
int pid
Definition: proc.h:108
Size ProcGlobalShmemSize(void)
Definition: proc.c:102
XLogRecPtr waitLSN
Definition: proc.h:147
PGPROC * lockGroupLeader
Definition: proc.h:188
LocalTransactionId fpLocalTransactionId
Definition: proc.h:181
TransactionId procArrayGroupMemberXid
Definition: proc.h:170
LOCKMASK heldLocks
Definition: proc.h:138
#define NUM_LOCK_PARTITIONS
Definition: lwlock.h:117
Definition: proc.h:37
LocalTransactionId lxid
Definition: proc.h:105
struct PGXACT PGXACT