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lwlock.h
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1 /*-------------------------------------------------------------------------
2  *
3  * lwlock.h
4  * Lightweight lock manager
5  *
6  *
7  * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
8  * Portions Copyright (c) 1994, Regents of the University of California
9  *
10  * src/include/storage/lwlock.h
11  *
12  *-------------------------------------------------------------------------
13  */
14 #ifndef LWLOCK_H
15 #define LWLOCK_H
16 
17 #ifdef FRONTEND
18 #error "lwlock.h may not be included from frontend code"
19 #endif
20 
21 #include "port/atomics.h"
22 #include "storage/proclist_types.h"
23 
24 struct PGPROC;
25 
26 /* what state of the wait process is a backend in */
27 typedef enum LWLockWaitState
28 {
29  LW_WS_NOT_WAITING, /* not currently waiting / woken up */
30  LW_WS_WAITING, /* currently waiting */
31  LW_WS_PENDING_WAKEUP, /* removed from waitlist, but not yet signalled */
33 
34 /*
35  * Code outside of lwlock.c should not manipulate the contents of this
36  * structure directly, but we have to declare it here to allow LWLocks to be
37  * incorporated into other data structures.
38  */
39 typedef struct LWLock
40 {
41  uint16 tranche; /* tranche ID */
42  pg_atomic_uint32 state; /* state of exclusive/nonexclusive lockers */
43  proclist_head waiters; /* list of waiting PGPROCs */
44 #ifdef LOCK_DEBUG
45  pg_atomic_uint32 nwaiters; /* number of waiters */
46  struct PGPROC *owner; /* last exclusive owner of the lock */
47 #endif
49 
50 /*
51  * In most cases, it's desirable to force each tranche of LWLocks to be aligned
52  * on a cache line boundary and make the array stride a power of 2. This saves
53  * a few cycles in indexing, but more importantly ensures that individual
54  * LWLocks don't cross cache line boundaries. This reduces cache contention
55  * problems, especially on AMD Opterons. In some cases, it's useful to add
56  * even more padding so that each LWLock takes up an entire cache line; this is
57  * useful, for example, in the main LWLock array, where the overall number of
58  * locks is small but some are heavily contended.
59  */
60 #define LWLOCK_PADDED_SIZE PG_CACHE_LINE_SIZE
61 
62 /* LWLock, padded to a full cache line size */
63 typedef union LWLockPadded
64 {
68 
70 
71 /* struct for storing named tranche information */
72 typedef struct NamedLWLockTranche
73 {
74  int trancheId;
75  char *trancheName;
77 
80 
81 /* Names for fixed lwlocks */
82 #include "storage/lwlocknames.h"
83 
84 /*
85  * It's a bit odd to declare NUM_BUFFER_PARTITIONS and NUM_LOCK_PARTITIONS
86  * here, but we need them to figure out offsets within MainLWLockArray, and
87  * having this file include lock.h or bufmgr.h would be backwards.
88  */
89 
90 /* Number of partitions of the shared buffer mapping hashtable */
91 #define NUM_BUFFER_PARTITIONS 128
92 
93 /* Number of partitions the shared lock tables are divided into */
94 #define LOG2_NUM_LOCK_PARTITIONS 4
95 #define NUM_LOCK_PARTITIONS (1 << LOG2_NUM_LOCK_PARTITIONS)
96 
97 /* Number of partitions the shared predicate lock tables are divided into */
98 #define LOG2_NUM_PREDICATELOCK_PARTITIONS 4
99 #define NUM_PREDICATELOCK_PARTITIONS (1 << LOG2_NUM_PREDICATELOCK_PARTITIONS)
100 
101 /* Offsets for various chunks of preallocated lwlocks. */
102 #define BUFFER_MAPPING_LWLOCK_OFFSET NUM_INDIVIDUAL_LWLOCKS
103 #define LOCK_MANAGER_LWLOCK_OFFSET \
104  (BUFFER_MAPPING_LWLOCK_OFFSET + NUM_BUFFER_PARTITIONS)
105 #define PREDICATELOCK_MANAGER_LWLOCK_OFFSET \
106  (LOCK_MANAGER_LWLOCK_OFFSET + NUM_LOCK_PARTITIONS)
107 #define NUM_FIXED_LWLOCKS \
108  (PREDICATELOCK_MANAGER_LWLOCK_OFFSET + NUM_PREDICATELOCK_PARTITIONS)
109 
110 typedef enum LWLockMode
111 {
114  LW_WAIT_UNTIL_FREE /* A special mode used in PGPROC->lwWaitMode,
115  * when waiting for lock to become free. Not
116  * to be used as LWLockAcquire argument */
118 
119 
120 #ifdef LOCK_DEBUG
121 extern PGDLLIMPORT bool Trace_lwlocks;
122 #endif
123 
124 extern bool LWLockAcquire(LWLock *lock, LWLockMode mode);
125 extern bool LWLockConditionalAcquire(LWLock *lock, LWLockMode mode);
126 extern bool LWLockAcquireOrWait(LWLock *lock, LWLockMode mode);
127 extern void LWLockRelease(LWLock *lock);
128 extern void LWLockReleaseClearVar(LWLock *lock, uint64 *valptr, uint64 val);
129 extern void LWLockReleaseAll(void);
130 extern bool LWLockHeldByMe(LWLock *lock);
131 extern bool LWLockAnyHeldByMe(LWLock *lock, int nlocks, size_t stride);
132 extern bool LWLockHeldByMeInMode(LWLock *lock, LWLockMode mode);
133 
134 extern bool LWLockWaitForVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval);
135 extern void LWLockUpdateVar(LWLock *lock, uint64 *valptr, uint64 val);
136 
137 extern Size LWLockShmemSize(void);
138 extern void CreateLWLocks(void);
139 extern void InitLWLockAccess(void);
140 
141 extern const char *GetLWLockIdentifier(uint32 classId, uint16 eventId);
142 
143 /*
144  * Extensions (or core code) can obtain an LWLocks by calling
145  * RequestNamedLWLockTranche() during postmaster startup. Subsequently,
146  * call GetNamedLWLockTranche() to obtain a pointer to an array containing
147  * the number of LWLocks requested.
148  */
149 extern void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks);
150 extern LWLockPadded *GetNamedLWLockTranche(const char *tranche_name);
151 
152 /*
153  * There is another, more flexible method of obtaining lwlocks. First, call
154  * LWLockNewTrancheId just once to obtain a tranche ID; this allocates from
155  * a shared counter. Next, each individual process using the tranche should
156  * call LWLockRegisterTranche() to associate that tranche ID with a name.
157  * Finally, LWLockInitialize should be called just once per lwlock, passing
158  * the tranche ID as an argument.
159  *
160  * It may seem strange that each process using the tranche must register it
161  * separately, but dynamic shared memory segments aren't guaranteed to be
162  * mapped at the same address in all coordinating backends, so storing the
163  * registration in the main shared memory segment wouldn't work for that case.
164  */
165 extern int LWLockNewTrancheId(void);
166 extern void LWLockRegisterTranche(int tranche_id, const char *tranche_name);
167 extern void LWLockInitialize(LWLock *lock, int tranche_id);
168 
169 /*
170  * Every tranche ID less than NUM_INDIVIDUAL_LWLOCKS is reserved; also,
171  * we reserve additional tranche IDs for builtin tranches not included in
172  * the set of individual LWLocks. A call to LWLockNewTrancheId will never
173  * return a value less than LWTRANCHE_FIRST_USER_DEFINED.
174  */
175 typedef enum BuiltinTrancheIds
176 {
177  LWTRANCHE_XACT_BUFFER = NUM_INDIVIDUAL_LWLOCKS,
206 
207 /*
208  * Prior to PostgreSQL 9.4, we used an enum type called LWLockId to refer
209  * to LWLocks. New code should instead use LWLock *. However, for the
210  * convenience of third-party code, we include the following typedef.
211  */
212 typedef LWLock *LWLockId;
213 
214 #endif /* LWLOCK_H */
unsigned short uint16
Definition: c.h:441
unsigned int uint32
Definition: c.h:442
#define PGDLLIMPORT
Definition: c.h:1252
size_t Size
Definition: c.h:541
#define newval
long val
Definition: informix.c:664
union LWLockPadded LWLockPadded
bool LWLockHeldByMe(LWLock *lock)
Definition: lwlock.c:1918
const char * GetLWLockIdentifier(uint32 classId, uint16 eventId)
Definition: lwlock.c:793
LWLockPadded * GetNamedLWLockTranche(const char *tranche_name)
Definition: lwlock.c:596
bool LWLockAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1194
void CreateLWLocks(void)
Definition: lwlock.c:467
LWLockWaitState
Definition: lwlock.h:28
@ LW_WS_NOT_WAITING
Definition: lwlock.h:29
@ LW_WS_WAITING
Definition: lwlock.h:30
@ LW_WS_PENDING_WAKEUP
Definition: lwlock.h:31
PGDLLIMPORT NamedLWLockTranche * NamedLWLockTrancheArray
Definition: lwlock.c:244
struct NamedLWLockTranche NamedLWLockTranche
#define LWLOCK_PADDED_SIZE
Definition: lwlock.h:60
void LWLockRegisterTranche(int tranche_id, const char *tranche_name)
Definition: lwlock.c:650
bool LWLockHeldByMeInMode(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1962
PGDLLIMPORT int NamedLWLockTrancheRequests
Definition: lwlock.c:241
int LWLockNewTrancheId(void)
Definition: lwlock.c:626
void RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)
Definition: lwlock.c:692
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1802
void LWLockUpdateVar(LWLock *lock, uint64 *valptr, uint64 val)
Definition: lwlock.c:1744
BuiltinTrancheIds
Definition: lwlock.h:176
@ LWTRANCHE_FIRST_USER_DEFINED
Definition: lwlock.h:204
@ LWTRANCHE_SHARED_TIDBITMAP
Definition: lwlock.h:198
@ LWTRANCHE_PER_SESSION_DSA
Definition: lwlock.h:194
@ LWTRANCHE_PARALLEL_QUERY_DSA
Definition: lwlock.h:193
@ LWTRANCHE_COMMITTS_BUFFER
Definition: lwlock.h:178
@ LWTRANCHE_PGSTATS_HASH
Definition: lwlock.h:202
@ LWTRANCHE_SUBTRANS_BUFFER
Definition: lwlock.h:179
@ LWTRANCHE_PER_SESSION_RECORD_TYPMOD
Definition: lwlock.h:196
@ LWTRANCHE_XACT_BUFFER
Definition: lwlock.h:177
@ LWTRANCHE_REPLICATION_ORIGIN_STATE
Definition: lwlock.h:186
@ LWTRANCHE_PARALLEL_APPEND
Definition: lwlock.h:199
@ LWTRANCHE_REPLICATION_SLOT_IO
Definition: lwlock.h:187
@ LWTRANCHE_BUFFER_CONTENT
Definition: lwlock.h:185
@ LWTRANCHE_MULTIXACTMEMBER_BUFFER
Definition: lwlock.h:181
@ LWTRANCHE_NOTIFY_BUFFER
Definition: lwlock.h:182
@ LWTRANCHE_PER_SESSION_RECORD_TYPE
Definition: lwlock.h:195
@ LWTRANCHE_PREDICATE_LOCK_MANAGER
Definition: lwlock.h:191
@ LWTRANCHE_BUFFER_MAPPING
Definition: lwlock.h:189
@ LWTRANCHE_SERIAL_BUFFER
Definition: lwlock.h:183
@ LWTRANCHE_PGSTATS_DSA
Definition: lwlock.h:201
@ LWTRANCHE_PARALLEL_HASH_JOIN
Definition: lwlock.h:192
@ LWTRANCHE_PGSTATS_DATA
Definition: lwlock.h:203
@ LWTRANCHE_PER_XACT_PREDICATE_LIST
Definition: lwlock.h:200
@ LWTRANCHE_MULTIXACTOFFSET_BUFFER
Definition: lwlock.h:180
@ LWTRANCHE_WAL_INSERT
Definition: lwlock.h:184
@ LWTRANCHE_LOCK_MANAGER
Definition: lwlock.h:190
@ LWTRANCHE_SHARED_TUPLESTORE
Definition: lwlock.h:197
@ LWTRANCHE_LOCK_FASTPATH
Definition: lwlock.h:188
void LWLockReleaseAll(void)
Definition: lwlock.c:1901
void LWLockInitialize(LWLock *lock, int tranche_id)
Definition: lwlock.c:729
bool LWLockConditionalAcquire(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1365
bool LWLockAcquireOrWait(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1422
LWLockMode
Definition: lwlock.h:111
@ LW_SHARED
Definition: lwlock.h:113
@ LW_WAIT_UNTIL_FREE
Definition: lwlock.h:114
@ LW_EXCLUSIVE
Definition: lwlock.h:112
PGDLLIMPORT LWLockPadded * MainLWLockArray
Definition: lwlock.c:205
LWLock * LWLockId
Definition: lwlock.h:212
bool LWLockWaitForVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval)
Definition: lwlock.c:1609
struct LWLock LWLock
void LWLockReleaseClearVar(LWLock *lock, uint64 *valptr, uint64 val)
Definition: lwlock.c:1875
Size LWLockShmemSize(void)
Definition: lwlock.c:437
bool LWLockAnyHeldByMe(LWLock *lock, int nlocks, size_t stride)
Definition: lwlock.c:1936
void InitLWLockAccess(void)
Definition: lwlock.c:580
static PgChecksumMode mode
Definition: pg_checksums.c:65
Definition: lwlock.h:40
pg_atomic_uint32 state
Definition: lwlock.h:42
uint16 tranche
Definition: lwlock.h:41
proclist_head waiters
Definition: lwlock.h:43
char * trancheName
Definition: lwlock.h:75
Definition: proc.h:162
LWLock lock
Definition: lwlock.h:65
char pad[LWLOCK_PADDED_SIZE]
Definition: lwlock.h:66