PostgreSQL Source Code  git master
lwlock.h File Reference
#include "port/atomics.h"
#include "storage/proclist_types.h"
#include "storage/lwlocknames.h"
Include dependency graph for lwlock.h:
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Data Structures

struct  LWLock
 
union  LWLockPadded
 
struct  NamedLWLockTranche
 

Macros

#define LWLOCK_PADDED_SIZE   PG_CACHE_LINE_SIZE
 
#define NUM_BUFFER_PARTITIONS   128
 
#define LOG2_NUM_LOCK_PARTITIONS   4
 
#define NUM_LOCK_PARTITIONS   (1 << LOG2_NUM_LOCK_PARTITIONS)
 
#define LOG2_NUM_PREDICATELOCK_PARTITIONS   4
 
#define NUM_PREDICATELOCK_PARTITIONS   (1 << LOG2_NUM_PREDICATELOCK_PARTITIONS)
 
#define BUFFER_MAPPING_LWLOCK_OFFSET   NUM_INDIVIDUAL_LWLOCKS
 
#define LOCK_MANAGER_LWLOCK_OFFSET    (BUFFER_MAPPING_LWLOCK_OFFSET + NUM_BUFFER_PARTITIONS)
 
#define PREDICATELOCK_MANAGER_LWLOCK_OFFSET    (LOCK_MANAGER_LWLOCK_OFFSET + NUM_LOCK_PARTITIONS)
 
#define NUM_FIXED_LWLOCKS    (PREDICATELOCK_MANAGER_LWLOCK_OFFSET + NUM_PREDICATELOCK_PARTITIONS)
 

Typedefs

typedef struct LWLock LWLock
 
typedef union LWLockPadded LWLockPadded
 
typedef struct NamedLWLockTranche NamedLWLockTranche
 
typedef enum LWLockMode LWLockMode
 
typedef enum BuiltinTrancheIds BuiltinTrancheIds
 
typedef LWLockLWLockId
 

Enumerations

enum  LWLockMode { LW_EXCLUSIVE , LW_SHARED , LW_WAIT_UNTIL_FREE }
 
enum  BuiltinTrancheIds {
  LWTRANCHE_XACT_BUFFER = NUM_INDIVIDUAL_LWLOCKS , LWTRANCHE_COMMITTS_BUFFER , LWTRANCHE_SUBTRANS_BUFFER , LWTRANCHE_MULTIXACTOFFSET_BUFFER ,
  LWTRANCHE_MULTIXACTMEMBER_BUFFER , LWTRANCHE_NOTIFY_BUFFER , LWTRANCHE_SERIAL_BUFFER , LWTRANCHE_WAL_INSERT ,
  LWTRANCHE_BUFFER_CONTENT , LWTRANCHE_REPLICATION_ORIGIN_STATE , LWTRANCHE_REPLICATION_SLOT_IO , LWTRANCHE_LOCK_FASTPATH ,
  LWTRANCHE_BUFFER_MAPPING , LWTRANCHE_LOCK_MANAGER , LWTRANCHE_PREDICATE_LOCK_MANAGER , LWTRANCHE_PARALLEL_HASH_JOIN ,
  LWTRANCHE_PARALLEL_QUERY_DSA , LWTRANCHE_PER_SESSION_DSA , LWTRANCHE_PER_SESSION_RECORD_TYPE , LWTRANCHE_PER_SESSION_RECORD_TYPMOD ,
  LWTRANCHE_SHARED_TUPLESTORE , LWTRANCHE_SHARED_TIDBITMAP , LWTRANCHE_PARALLEL_APPEND , LWTRANCHE_PER_XACT_PREDICATE_LIST ,
  LWTRANCHE_PGSTATS_DSA , LWTRANCHE_PGSTATS_HASH , LWTRANCHE_PGSTATS_DATA , LWTRANCHE_FIRST_USER_DEFINED
}
 

Functions

bool LWLockAcquire (LWLock *lock, LWLockMode mode)
 
bool LWLockConditionalAcquire (LWLock *lock, LWLockMode mode)
 
bool LWLockAcquireOrWait (LWLock *lock, LWLockMode mode)
 
void LWLockRelease (LWLock *lock)
 
void LWLockReleaseClearVar (LWLock *lock, uint64 *valptr, uint64 val)
 
void LWLockReleaseAll (void)
 
bool LWLockHeldByMe (LWLock *lock)
 
bool LWLockHeldByMeInMode (LWLock *lock, LWLockMode mode)
 
int LWLockHeldCount (void)
 
bool LWLockWaitForVar (LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval)
 
void LWLockUpdateVar (LWLock *lock, uint64 *valptr, uint64 value)
 
Size LWLockShmemSize (void)
 
void CreateLWLocks (void)
 
void InitLWLockAccess (void)
 
const char * GetLWLockIdentifier (uint32 classId, uint16 eventId)
 
void RequestNamedLWLockTranche (const char *tranche_name, int num_lwlocks)
 
LWLockPaddedGetNamedLWLockTranche (const char *tranche_name)
 
int LWLockNewTrancheId (void)
 
void LWLockRegisterTranche (int tranche_id, const char *tranche_name)
 
void LWLockInitialize (LWLock *lock, int tranche_id)
 

Variables

PGDLLIMPORT LWLockPaddedMainLWLockArray
 
PGDLLIMPORT NamedLWLockTrancheNamedLWLockTrancheArray
 
PGDLLIMPORT int NamedLWLockTrancheRequests
 

Macro Definition Documentation

◆ BUFFER_MAPPING_LWLOCK_OFFSET

#define BUFFER_MAPPING_LWLOCK_OFFSET   NUM_INDIVIDUAL_LWLOCKS

Definition at line 94 of file lwlock.h.

◆ LOCK_MANAGER_LWLOCK_OFFSET

#define LOCK_MANAGER_LWLOCK_OFFSET    (BUFFER_MAPPING_LWLOCK_OFFSET + NUM_BUFFER_PARTITIONS)

Definition at line 95 of file lwlock.h.

◆ LOG2_NUM_LOCK_PARTITIONS

#define LOG2_NUM_LOCK_PARTITIONS   4

Definition at line 86 of file lwlock.h.

◆ LOG2_NUM_PREDICATELOCK_PARTITIONS

#define LOG2_NUM_PREDICATELOCK_PARTITIONS   4

Definition at line 90 of file lwlock.h.

◆ LWLOCK_PADDED_SIZE

#define LWLOCK_PADDED_SIZE   PG_CACHE_LINE_SIZE

Definition at line 52 of file lwlock.h.

◆ NUM_BUFFER_PARTITIONS

#define NUM_BUFFER_PARTITIONS   128

Definition at line 83 of file lwlock.h.

◆ NUM_FIXED_LWLOCKS

Definition at line 99 of file lwlock.h.

◆ NUM_LOCK_PARTITIONS

#define NUM_LOCK_PARTITIONS   (1 << LOG2_NUM_LOCK_PARTITIONS)

Definition at line 87 of file lwlock.h.

◆ NUM_PREDICATELOCK_PARTITIONS

#define NUM_PREDICATELOCK_PARTITIONS   (1 << LOG2_NUM_PREDICATELOCK_PARTITIONS)

Definition at line 91 of file lwlock.h.

◆ PREDICATELOCK_MANAGER_LWLOCK_OFFSET

#define PREDICATELOCK_MANAGER_LWLOCK_OFFSET    (LOCK_MANAGER_LWLOCK_OFFSET + NUM_LOCK_PARTITIONS)

Definition at line 97 of file lwlock.h.

Typedef Documentation

◆ BuiltinTrancheIds

◆ LWLock

typedef struct LWLock LWLock

◆ LWLockId

typedef LWLock* LWLockId

Definition at line 204 of file lwlock.h.

◆ LWLockMode

typedef enum LWLockMode LWLockMode

◆ LWLockPadded

typedef union LWLockPadded LWLockPadded

◆ NamedLWLockTranche

Enumeration Type Documentation

◆ BuiltinTrancheIds

Enumerator
LWTRANCHE_XACT_BUFFER 
LWTRANCHE_COMMITTS_BUFFER 
LWTRANCHE_SUBTRANS_BUFFER 
LWTRANCHE_MULTIXACTOFFSET_BUFFER 
LWTRANCHE_MULTIXACTMEMBER_BUFFER 
LWTRANCHE_NOTIFY_BUFFER 
LWTRANCHE_SERIAL_BUFFER 
LWTRANCHE_WAL_INSERT 
LWTRANCHE_BUFFER_CONTENT 
LWTRANCHE_REPLICATION_ORIGIN_STATE 
LWTRANCHE_REPLICATION_SLOT_IO 
LWTRANCHE_LOCK_FASTPATH 
LWTRANCHE_BUFFER_MAPPING 
LWTRANCHE_LOCK_MANAGER 
LWTRANCHE_PREDICATE_LOCK_MANAGER 
LWTRANCHE_PARALLEL_HASH_JOIN 
LWTRANCHE_PARALLEL_QUERY_DSA 
LWTRANCHE_PER_SESSION_DSA 
LWTRANCHE_PER_SESSION_RECORD_TYPE 
LWTRANCHE_PER_SESSION_RECORD_TYPMOD 
LWTRANCHE_SHARED_TUPLESTORE 
LWTRANCHE_SHARED_TIDBITMAP 
LWTRANCHE_PARALLEL_APPEND 
LWTRANCHE_PER_XACT_PREDICATE_LIST 
LWTRANCHE_PGSTATS_DSA 
LWTRANCHE_PGSTATS_HASH 
LWTRANCHE_PGSTATS_DATA 
LWTRANCHE_FIRST_USER_DEFINED 

Definition at line 167 of file lwlock.h.

168 {
169  LWTRANCHE_XACT_BUFFER = NUM_INDIVIDUAL_LWLOCKS,
BuiltinTrancheIds
Definition: lwlock.h:168
@ LWTRANCHE_FIRST_USER_DEFINED
Definition: lwlock.h:196
@ LWTRANCHE_SHARED_TIDBITMAP
Definition: lwlock.h:190
@ LWTRANCHE_PER_SESSION_DSA
Definition: lwlock.h:186
@ LWTRANCHE_PARALLEL_QUERY_DSA
Definition: lwlock.h:185
@ LWTRANCHE_COMMITTS_BUFFER
Definition: lwlock.h:170
@ LWTRANCHE_PGSTATS_HASH
Definition: lwlock.h:194
@ LWTRANCHE_SUBTRANS_BUFFER
Definition: lwlock.h:171
@ LWTRANCHE_PER_SESSION_RECORD_TYPMOD
Definition: lwlock.h:188
@ LWTRANCHE_XACT_BUFFER
Definition: lwlock.h:169
@ LWTRANCHE_REPLICATION_ORIGIN_STATE
Definition: lwlock.h:178
@ LWTRANCHE_PARALLEL_APPEND
Definition: lwlock.h:191
@ LWTRANCHE_REPLICATION_SLOT_IO
Definition: lwlock.h:179
@ LWTRANCHE_BUFFER_CONTENT
Definition: lwlock.h:177
@ LWTRANCHE_MULTIXACTMEMBER_BUFFER
Definition: lwlock.h:173
@ LWTRANCHE_NOTIFY_BUFFER
Definition: lwlock.h:174
@ LWTRANCHE_PER_SESSION_RECORD_TYPE
Definition: lwlock.h:187
@ LWTRANCHE_PREDICATE_LOCK_MANAGER
Definition: lwlock.h:183
@ LWTRANCHE_BUFFER_MAPPING
Definition: lwlock.h:181
@ LWTRANCHE_SERIAL_BUFFER
Definition: lwlock.h:175
@ LWTRANCHE_PGSTATS_DSA
Definition: lwlock.h:193
@ LWTRANCHE_PARALLEL_HASH_JOIN
Definition: lwlock.h:184
@ LWTRANCHE_PGSTATS_DATA
Definition: lwlock.h:195
@ LWTRANCHE_PER_XACT_PREDICATE_LIST
Definition: lwlock.h:192
@ LWTRANCHE_MULTIXACTOFFSET_BUFFER
Definition: lwlock.h:172
@ LWTRANCHE_WAL_INSERT
Definition: lwlock.h:176
@ LWTRANCHE_LOCK_MANAGER
Definition: lwlock.h:182
@ LWTRANCHE_SHARED_TUPLESTORE
Definition: lwlock.h:189
@ LWTRANCHE_LOCK_FASTPATH
Definition: lwlock.h:180

◆ LWLockMode

enum LWLockMode
Enumerator
LW_EXCLUSIVE 
LW_SHARED 
LW_WAIT_UNTIL_FREE 

Definition at line 102 of file lwlock.h.

103 {
104  LW_EXCLUSIVE,
105  LW_SHARED,
106  LW_WAIT_UNTIL_FREE /* A special mode used in PGPROC->lwWaitMode,
107  * when waiting for lock to become free. Not
108  * to be used as LWLockAcquire argument */
109 } LWLockMode;
LWLockMode
Definition: lwlock.h:103
@ LW_SHARED
Definition: lwlock.h:105
@ LW_WAIT_UNTIL_FREE
Definition: lwlock.h:106
@ LW_EXCLUSIVE
Definition: lwlock.h:104

Function Documentation

◆ CreateLWLocks()

void CreateLWLocks ( void  )

Definition at line 467 of file lwlock.c.

468 {
470  "MAX_BACKENDS too big for lwlock.c");
471 
473  "Miscalculated LWLock padding");
474 
475  if (!IsUnderPostmaster)
476  {
477  Size spaceLocks = LWLockShmemSize();
478  int *LWLockCounter;
479  char *ptr;
480 
481  /* Allocate space */
482  ptr = (char *) ShmemAlloc(spaceLocks);
483 
484  /* Leave room for dynamic allocation of tranches */
485  ptr += sizeof(int);
486 
487  /* Ensure desired alignment of LWLock array */
488  ptr += LWLOCK_PADDED_SIZE - ((uintptr_t) ptr) % LWLOCK_PADDED_SIZE;
489 
490  MainLWLockArray = (LWLockPadded *) ptr;
491 
492  /*
493  * Initialize the dynamic-allocation counter for tranches, which is
494  * stored just before the first LWLock.
495  */
496  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
497  *LWLockCounter = LWTRANCHE_FIRST_USER_DEFINED;
498 
499  /* Initialize all LWLocks */
501  }
502 
503  /* Register named extension LWLock tranches in the current process. */
504  for (int i = 0; i < NamedLWLockTrancheRequests; i++)
506  NamedLWLockTrancheArray[i].trancheName);
507 }
unsigned int uint32
Definition: c.h:441
#define StaticAssertStmt(condition, errmessage)
Definition: c.h:918
size_t Size
Definition: c.h:540
bool IsUnderPostmaster
Definition: globals.c:113
int i
Definition: isn.c:73
#define LW_VAL_EXCLUSIVE
Definition: lwlock.c:104
NamedLWLockTranche * NamedLWLockTrancheArray
Definition: lwlock.c:244
void LWLockRegisterTranche(int tranche_id, const char *tranche_name)
Definition: lwlock.c:650
int NamedLWLockTrancheRequests
Definition: lwlock.c:241
static void InitializeLWLocks(void)
Definition: lwlock.c:513
LWLockPadded * MainLWLockArray
Definition: lwlock.c:205
Size LWLockShmemSize(void)
Definition: lwlock.c:437
#define LWLOCK_PADDED_SIZE
Definition: lwlock.h:52
#define MAX_BACKENDS
Definition: postmaster.h:75
void * ShmemAlloc(Size size)
Definition: shmem.c:161
Definition: lwlock.h:32

References i, InitializeLWLocks(), IsUnderPostmaster, LW_VAL_EXCLUSIVE, LWLOCK_PADDED_SIZE, LWLockRegisterTranche(), LWLockShmemSize(), LWTRANCHE_FIRST_USER_DEFINED, MainLWLockArray, MAX_BACKENDS, NamedLWLockTrancheArray, NamedLWLockTrancheRequests, ShmemAlloc(), and StaticAssertStmt.

Referenced by CreateSharedMemoryAndSemaphores().

◆ GetLWLockIdentifier()

const char* GetLWLockIdentifier ( uint32  classId,
uint16  eventId 
)

Definition at line 798 of file lwlock.c.

799 {
800  Assert(classId == PG_WAIT_LWLOCK);
801  /* The event IDs are just tranche numbers. */
802  return GetLWTrancheName(eventId);
803 }
Assert(fmt[strlen(fmt) - 1] !='\n')
static const char * GetLWTrancheName(uint16 trancheId)
Definition: lwlock.c:770
#define PG_WAIT_LWLOCK
Definition: wait_event.h:18

References Assert(), GetLWTrancheName(), and PG_WAIT_LWLOCK.

Referenced by pgstat_get_wait_event().

◆ GetNamedLWLockTranche()

LWLockPadded* GetNamedLWLockTranche ( const char *  tranche_name)

Definition at line 596 of file lwlock.c.

597 {
598  int lock_pos;
599  int i;
600 
601  /*
602  * Obtain the position of base address of LWLock belonging to requested
603  * tranche_name in MainLWLockArray. LWLocks for named tranches are placed
604  * in MainLWLockArray after fixed locks.
605  */
606  lock_pos = NUM_FIXED_LWLOCKS;
607  for (i = 0; i < NamedLWLockTrancheRequests; i++)
608  {
609  if (strcmp(NamedLWLockTrancheRequestArray[i].tranche_name,
610  tranche_name) == 0)
611  return &MainLWLockArray[lock_pos];
612 
614  }
615 
616  elog(ERROR, "requested tranche is not registered");
617 
618  /* just to keep compiler quiet */
619  return NULL;
620 }
#define ERROR
Definition: elog.h:33
#define elog(elevel,...)
Definition: elog.h:218
static NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:232
#define NUM_FIXED_LWLOCKS
Definition: lwlock.h:99

References elog, ERROR, i, MainLWLockArray, NamedLWLockTrancheRequestArray, NamedLWLockTrancheRequests, NUM_FIXED_LWLOCKS, and NamedLWLockTrancheRequest::num_lwlocks.

Referenced by pgss_shmem_startup().

◆ InitLWLockAccess()

void InitLWLockAccess ( void  )

Definition at line 580 of file lwlock.c.

581 {
582 #ifdef LWLOCK_STATS
583  init_lwlock_stats();
584 #endif
585 }

Referenced by InitProcess().

◆ LWLockAcquire()

bool LWLockAcquire ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1196 of file lwlock.c.

1197 {
1198  PGPROC *proc = MyProc;
1199  bool result = true;
1200  int extraWaits = 0;
1201 #ifdef LWLOCK_STATS
1202  lwlock_stats *lwstats;
1203 
1204  lwstats = get_lwlock_stats_entry(lock);
1205 #endif
1206 
1208 
1209  PRINT_LWDEBUG("LWLockAcquire", lock, mode);
1210 
1211 #ifdef LWLOCK_STATS
1212  /* Count lock acquisition attempts */
1213  if (mode == LW_EXCLUSIVE)
1214  lwstats->ex_acquire_count++;
1215  else
1216  lwstats->sh_acquire_count++;
1217 #endif /* LWLOCK_STATS */
1218 
1219  /*
1220  * We can't wait if we haven't got a PGPROC. This should only occur
1221  * during bootstrap or shared memory initialization. Put an Assert here
1222  * to catch unsafe coding practices.
1223  */
1224  Assert(!(proc == NULL && IsUnderPostmaster));
1225 
1226  /* Ensure we will have room to remember the lock */
1228  elog(ERROR, "too many LWLocks taken");
1229 
1230  /*
1231  * Lock out cancel/die interrupts until we exit the code section protected
1232  * by the LWLock. This ensures that interrupts will not interfere with
1233  * manipulations of data structures in shared memory.
1234  */
1235  HOLD_INTERRUPTS();
1236 
1237  /*
1238  * Loop here to try to acquire lock after each time we are signaled by
1239  * LWLockRelease.
1240  *
1241  * NOTE: it might seem better to have LWLockRelease actually grant us the
1242  * lock, rather than retrying and possibly having to go back to sleep. But
1243  * in practice that is no good because it means a process swap for every
1244  * lock acquisition when two or more processes are contending for the same
1245  * lock. Since LWLocks are normally used to protect not-very-long
1246  * sections of computation, a process needs to be able to acquire and
1247  * release the same lock many times during a single CPU time slice, even
1248  * in the presence of contention. The efficiency of being able to do that
1249  * outweighs the inefficiency of sometimes wasting a process dispatch
1250  * cycle because the lock is not free when a released waiter finally gets
1251  * to run. See pgsql-hackers archives for 29-Dec-01.
1252  */
1253  for (;;)
1254  {
1255  bool mustwait;
1256 
1257  /*
1258  * Try to grab the lock the first time, we're not in the waitqueue
1259  * yet/anymore.
1260  */
1261  mustwait = LWLockAttemptLock(lock, mode);
1262 
1263  if (!mustwait)
1264  {
1265  LOG_LWDEBUG("LWLockAcquire", lock, "immediately acquired lock");
1266  break; /* got the lock */
1267  }
1268 
1269  /*
1270  * Ok, at this point we couldn't grab the lock on the first try. We
1271  * cannot simply queue ourselves to the end of the list and wait to be
1272  * woken up because by now the lock could long have been released.
1273  * Instead add us to the queue and try to grab the lock again. If we
1274  * succeed we need to revert the queuing and be happy, otherwise we
1275  * recheck the lock. If we still couldn't grab it, we know that the
1276  * other locker will see our queue entries when releasing since they
1277  * existed before we checked for the lock.
1278  */
1279 
1280  /* add to the queue */
1281  LWLockQueueSelf(lock, mode);
1282 
1283  /* we're now guaranteed to be woken up if necessary */
1284  mustwait = LWLockAttemptLock(lock, mode);
1285 
1286  /* ok, grabbed the lock the second time round, need to undo queueing */
1287  if (!mustwait)
1288  {
1289  LOG_LWDEBUG("LWLockAcquire", lock, "acquired, undoing queue");
1290 
1291  LWLockDequeueSelf(lock);
1292  break;
1293  }
1294 
1295  /*
1296  * Wait until awakened.
1297  *
1298  * It is possible that we get awakened for a reason other than being
1299  * signaled by LWLockRelease. If so, loop back and wait again. Once
1300  * we've gotten the LWLock, re-increment the sema by the number of
1301  * additional signals received.
1302  */
1303  LOG_LWDEBUG("LWLockAcquire", lock, "waiting");
1304 
1305 #ifdef LWLOCK_STATS
1306  lwstats->block_count++;
1307 #endif
1308 
1309  LWLockReportWaitStart(lock);
1310  if (TRACE_POSTGRESQL_LWLOCK_WAIT_START_ENABLED())
1311  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1312 
1313  for (;;)
1314  {
1315  PGSemaphoreLock(proc->sem);
1316  if (!proc->lwWaiting)
1317  break;
1318  extraWaits++;
1319  }
1320 
1321  /* Retrying, allow LWLockRelease to release waiters again. */
1323 
1324 #ifdef LOCK_DEBUG
1325  {
1326  /* not waiting anymore */
1327  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1328 
1329  Assert(nwaiters < MAX_BACKENDS);
1330  }
1331 #endif
1332 
1333  if (TRACE_POSTGRESQL_LWLOCK_WAIT_DONE_ENABLED())
1334  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1336 
1337  LOG_LWDEBUG("LWLockAcquire", lock, "awakened");
1338 
1339  /* Now loop back and try to acquire lock again. */
1340  result = false;
1341  }
1342 
1343  if (TRACE_POSTGRESQL_LWLOCK_ACQUIRE_ENABLED())
1344  TRACE_POSTGRESQL_LWLOCK_ACQUIRE(T_NAME(lock), mode);
1345 
1346  /* Add lock to list of locks held by this backend */
1349 
1350  /*
1351  * Fix the process wait semaphore's count for any absorbed wakeups.
1352  */
1353  while (extraWaits-- > 0)
1354  PGSemaphoreUnlock(proc->sem);
1355 
1356  return result;
1357 }
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372
static uint32 pg_atomic_fetch_sub_u32(volatile pg_atomic_uint32 *ptr, int32 sub_)
Definition: atomics.h:343
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:155
#define AssertArg(condition)
Definition: c.h:806
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:223
static bool LWLockAttemptLock(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:815
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:761
#define LW_FLAG_RELEASE_OK
Definition: lwlock.c:101
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:213
#define T_NAME(lock)
Definition: lwlock.c:251
static int num_held_lwlocks
Definition: lwlock.c:222
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:316
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1058
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:315
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:752
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1101
#define HOLD_INTERRUPTS()
Definition: miscadmin.h:132
static PgChecksumMode mode
Definition: pg_checksums.c:65
void PGSemaphoreUnlock(PGSemaphore sema)
Definition: posix_sema.c:340
void PGSemaphoreLock(PGSemaphore sema)
Definition: posix_sema.c:320
PGPROC * MyProc
Definition: proc.c:68
LWLockMode mode
Definition: lwlock.c:219
LWLock * lock
Definition: lwlock.c:218
pg_atomic_uint32 state
Definition: lwlock.h:34
Definition: proc.h:160
bool lwWaiting
Definition: proc.h:208
PGSemaphore sem
Definition: proc.h:165

References Assert(), AssertArg, elog, ERROR, held_lwlocks, HOLD_INTERRUPTS, IsUnderPostmaster, LWLockHandle::lock, LOG_LWDEBUG, LW_EXCLUSIVE, LW_FLAG_RELEASE_OK, LW_SHARED, LWLockAttemptLock(), LWLockDequeueSelf(), LWLockQueueSelf(), LWLockReportWaitEnd(), LWLockReportWaitStart(), PGPROC::lwWaiting, MAX_BACKENDS, MAX_SIMUL_LWLOCKS, LWLockHandle::mode, mode, MyProc, num_held_lwlocks, pg_atomic_fetch_or_u32(), pg_atomic_fetch_sub_u32(), PG_USED_FOR_ASSERTS_ONLY, PGSemaphoreLock(), PGSemaphoreUnlock(), PRINT_LWDEBUG, PGPROC::sem, LWLock::state, and T_NAME.

Referenced by _bt_end_vacuum(), _bt_start_vacuum(), _bt_vacuum_cycleid(), AbsorbSyncRequests(), ActivateCommitTs(), AdvanceNextFullTransactionIdPastXid(), AdvanceOldestClogXid(), AdvanceOldestCommitTsXid(), AdvanceXLInsertBuffer(), alloc_object(), AlterSystemSetConfigFile(), ApplyLauncherMain(), apw_detach_shmem(), apw_dump_now(), apw_init_shmem(), apw_load_buffers(), asyncQueueAddEntries(), asyncQueueAdvanceTail(), asyncQueueReadAllNotifications(), asyncQueueUnregister(), AtAbort_Twophase(), AtPrepare_PredicateLocks(), attach_internal(), autoprewarm_main(), autoprewarm_start_worker(), AutoVacLauncherMain(), AutoVacuumRequestWork(), AutoVacWorkerMain(), BackendIdGetProc(), BackendIdGetTransactionIds(), BackendPidGetProc(), BackendXidGetPid(), BecomeLockGroupLeader(), BecomeLockGroupMember(), BootStrapCLOG(), BootStrapMultiXact(), BootStrapSUBTRANS(), BootStrapXLOG(), BufferAlloc(), CancelDBBackends(), check_for_freed_segments(), CheckDeadLock(), CheckForSerializableConflictOut(), CheckPointPredicate(), CheckPointRelationMap(), CheckPointReplicationOrigin(), CheckPointReplicationSlots(), CheckPointTwoPhase(), CheckTableForSerializableConflictIn(), CheckTargetForConflictsIn(), choose_next_subplan_for_leader(), choose_next_subplan_for_worker(), CleanupInvalidationState(), ClearOldPredicateLocks(), clog_redo(), commit_ts_redo(), ComputeXidHorizons(), copy_replication_slot(), CountDBBackends(), CountDBConnections(), CountOtherDBBackends(), CountUserBackends(), CreateCheckPoint(), CreateEndOfRecoveryRecord(), CreateInitDecodingContext(), CreatePredicateLock(), CreateRestartPoint(), DeactivateCommitTs(), DeleteChildTargetLocks(), DeleteLockTarget(), destroy_superblock(), do_autovacuum(), do_pg_backup_start(), do_pg_backup_stop(), do_start_worker(), DropAllPredicateLocksFromTable(), DropSubscription(), DropTableSpace(), dsa_allocate_extended(), dsa_dump(), dsa_free(), dsa_pin(), dsa_release_in_place(), dsa_set_size_limit(), dsa_trim(), dsa_unpin(), dshash_delete_key(), dshash_dump(), dshash_find(), dshash_find_or_insert(), dshash_seq_next(), dsm_attach(), dsm_create(), dsm_detach(), dsm_pin_segment(), dsm_unpin_segment(), ensure_active_superblock(), entry_reset(), Exec_ListenPreCommit(), ExecParallelHashMergeCounters(), ExecParallelHashPopChunkQueue(), ExecParallelHashTupleAlloc(), ExecParallelHashTuplePrealloc(), ExpireAllKnownAssignedTransactionIds(), ExpireOldKnownAssignedTransactionIds(), ExpireTreeKnownAssignedTransactionIds(), ExtendCLOG(), ExtendCommitTs(), ExtendMultiXactMember(), ExtendMultiXactOffset(), ExtendSUBTRANS(), FastPathGetRelationLockEntry(), FastPathTransferRelationLocks(), FindAndDropRelFileNodeBuffers(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLockConflicts(), GetLockStatusData(), GetMultiXactIdMembers(), GetNewMultiXactId(), GetNewObjectId(), GetNewTransactionId(), GetOldestActiveTransactionId(), GetOldestMultiXactId(), GetOldestRestartPoint(), GetOldestSafeDecodingTransactionId(), GetOldSnapshotFromTimeMapping(), GetOldSnapshotTimeMapping(), GetPredicateLockStatusData(), GetPreparedTransactionList(), GetRunningTransactionData(), GetRunningTransactionLocks(), GetSafeSnapshot(), GetSafeSnapshotBlockingPids(), GetSerializableTransactionSnapshotInt(), GetSnapshotData(), GetVirtualXIDsDelayingChkpt(), HandleAutoVacLauncherInterrupts(), HaveVirtualXIDsDelayingChkpt(), InstallXLogFileSegment(), InvalidateBuffer(), InvalidateObsoleteReplicationSlots(), InvalidatePossiblyObsoleteSlot(), IsInstallXLogFileSegmentActive(), KnownAssignedXidsAdd(), KnownAssignedXidsReset(), lock_twophase_recover(), LockAcquireExtended(), LockBuffer(), LockErrorCleanup(), LockGXact(), LockHasWaiters(), LockRefindAndRelease(), LockRelease(), LockReleaseAll(), LockWaiterCount(), logicalrep_worker_attach(), logicalrep_worker_detach(), logicalrep_worker_launch(), logicalrep_worker_stop(), logicalrep_worker_wakeup(), LookupGXact(), MaintainOldSnapshotTimeMapping(), MarkAsPrepared(), MarkAsPreparing(), MaybeExtendOffsetSlru(), multixact_redo(), MultiXactAdvanceNextMXact(), MultiXactGetCheckptMulti(), MultiXactIdSetOldestMember(), MultiXactIdSetOldestVisible(), MultiXactSetNextMXact(), PageIsPredicateLocked(), perform_relmap_update(), pg_get_replication_slots(), pg_get_shmem_allocations(), pg_notification_queue_usage(), pg_show_replication_origin_status(), pg_stat_get_subscription(), pg_stat_statements_internal(), pg_xact_status(), pgss_shmem_startup(), pgss_store(), pgstat_archiver_reset_all_cb(), pgstat_archiver_snapshot_cb(), pgstat_bgwriter_reset_all_cb(), pgstat_bgwriter_snapshot_cb(), pgstat_checkpointer_reset_all_cb(), pgstat_checkpointer_snapshot_cb(), pgstat_flush_wal(), pgstat_lock_entry(), pgstat_reset_matching_entries(), pgstat_reset_slru_counter_internal(), pgstat_slru_flush(), pgstat_slru_snapshot_cb(), pgstat_wal_reset_all_cb(), pgstat_wal_snapshot_cb(), PostPrepare_Locks(), PostPrepare_MultiXact(), PostPrepare_Twophase(), PreCommit_CheckForSerializationFailure(), PreCommit_Notify(), predicatelock_twophase_recover(), PredicateLockPageSplit(), PredicateLockTwoPhaseFinish(), PrefetchSharedBuffer(), PrescanPreparedTransactions(), ProcArrayAdd(), ProcArrayApplyRecoveryInfo(), ProcArrayApplyXidAssignment(), ProcArrayClearTransaction(), ProcArrayEndTransaction(), ProcArrayGetReplicationSlotXmin(), ProcArrayGroupClearXid(), ProcArrayInstallImportedXmin(), ProcArrayInstallRestoredXmin(), ProcArrayRemove(), ProcArraySetReplicationSlotXmin(), process_syncing_tables_for_apply(), ProcKill(), ProcSleep(), ReachedEndOfBackup(), read_relmap_file(), ReadBuffer_common(), ReadMultiXactCounts(), ReadMultiXactIdRange(), ReadNextFullTransactionId(), ReadNextMultiXactId(), ReadReplicationSlot(), RecordNewMultiXact(), RecoverPreparedTransactions(), RegisterDynamicBackgroundWorker(), RegisterPredicateLockingXid(), RelationCacheInitFilePreInvalidate(), ReleaseOneSerializableXact(), ReleasePredicateLocks(), relmap_redo(), RemoveScratchTarget(), ReplicationOriginExitCleanup(), ReplicationSlotAcquire(), ReplicationSlotCleanup(), ReplicationSlotCreate(), ReplicationSlotDropPtr(), ReplicationSlotRelease(), ReplicationSlotsComputeLogicalRestartLSN(), ReplicationSlotsComputeRequiredLSN(), ReplicationSlotsComputeRequiredXmin(), ReplicationSlotsCountDBSlots(), ReplicationSlotsDropDBSlots(), replorigin_advance(), replorigin_drop_guts(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), resize(), RestoreScratchTarget(), restoreTwoPhaseData(), SaveSlotToPath(), SearchNamedReplicationSlot(), SerialAdd(), SerialGetMinConflictCommitSeqNo(), SerialSetActiveSerXmin(), set_indexsafe_procflags(), SetCommitTsLimit(), SetInstallXLogFileSegmentActive(), SetMultiXactIdLimit(), SetNextObjectId(), SetOffsetVacuumLimit(), SetTransactionIdLimit(), SetXidCommitTsInPage(), SharedInvalBackendInit(), ShmemInitStruct(), SICleanupQueue(), SIGetDataEntries(), SignalBackends(), SignalVirtualTransaction(), SIInsertDataEntries(), SimpleLruReadPage(), SimpleLruReadPage_ReadOnly(), SimpleLruTruncate(), SimpleLruWaitIO(), SimpleLruWriteAll(), SlruDeleteSegment(), SlruInternalWritePage(), SnapBuildInitialSnapshot(), ss_get_location(), StandbyRecoverPreparedTransactions(), StartupCLOG(), StartupDecodingContext(), StartupSUBTRANS(), StartupXLOG(), sts_parallel_scan_next(), SubTransSetParent(), SummarizeOldestCommittedSxact(), SwitchIntoArchiveRecovery(), SyncOneBuffer(), SyncRepCancelWait(), SyncRepCleanupAtProcExit(), SyncRepReleaseWaiters(), SyncRepUpdateSyncStandbysDefined(), SyncRepWaitForLSN(), TablespaceCreateDbspace(), tbm_shared_iterate(), TerminateBackgroundWorker(), TerminateOtherDBBackends(), TransactionGroupUpdateXidStatus(), TransactionIdGetCommitTsData(), TransactionIdIsActive(), TransactionIdIsInProgress(), TransactionIdSetPageStatus(), TransactionTreeSetCommitTsData(), TransferPredicateLocksToNewTarget(), TrimCLOG(), TrimMultiXact(), TruncateMultiXact(), TwoPhaseGetGXact(), TwoPhaseGetXidByVirtualXID(), update_cached_xid_range(), UpdateMinRecoveryPoint(), vac_truncate_clog(), vacuum_rel(), VirtualXactLock(), VirtualXactLockTableCleanup(), VirtualXactLockTableInsert(), wait_for_relation_state_change(), wait_for_worker_state_change(), WaitForReplicationWorkerAttach(), WALInsertLockAcquire(), WALInsertLockAcquireExclusive(), write_relcache_init_file(), xact_redo(), XidCacheRemoveRunningXids(), xlog_redo(), XLogBackgroundFlush(), XLogReportParameters(), and XLogShutdownWalRcv().

◆ LWLockAcquireOrWait()

bool LWLockAcquireOrWait ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1424 of file lwlock.c.

1425 {
1426  PGPROC *proc = MyProc;
1427  bool mustwait;
1428  int extraWaits = 0;
1429 #ifdef LWLOCK_STATS
1430  lwlock_stats *lwstats;
1431 
1432  lwstats = get_lwlock_stats_entry(lock);
1433 #endif
1434 
1436 
1437  PRINT_LWDEBUG("LWLockAcquireOrWait", lock, mode);
1438 
1439  /* Ensure we will have room to remember the lock */
1441  elog(ERROR, "too many LWLocks taken");
1442 
1443  /*
1444  * Lock out cancel/die interrupts until we exit the code section protected
1445  * by the LWLock. This ensures that interrupts will not interfere with
1446  * manipulations of data structures in shared memory.
1447  */
1448  HOLD_INTERRUPTS();
1449 
1450  /*
1451  * NB: We're using nearly the same twice-in-a-row lock acquisition
1452  * protocol as LWLockAcquire(). Check its comments for details.
1453  */
1454  mustwait = LWLockAttemptLock(lock, mode);
1455 
1456  if (mustwait)
1457  {
1459 
1460  mustwait = LWLockAttemptLock(lock, mode);
1461 
1462  if (mustwait)
1463  {
1464  /*
1465  * Wait until awakened. Like in LWLockAcquire, be prepared for
1466  * bogus wakeups.
1467  */
1468  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "waiting");
1469 
1470 #ifdef LWLOCK_STATS
1471  lwstats->block_count++;
1472 #endif
1473 
1474  LWLockReportWaitStart(lock);
1475  if (TRACE_POSTGRESQL_LWLOCK_WAIT_START_ENABLED())
1476  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1477 
1478  for (;;)
1479  {
1480  PGSemaphoreLock(proc->sem);
1481  if (!proc->lwWaiting)
1482  break;
1483  extraWaits++;
1484  }
1485 
1486 #ifdef LOCK_DEBUG
1487  {
1488  /* not waiting anymore */
1489  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1490 
1491  Assert(nwaiters < MAX_BACKENDS);
1492  }
1493 #endif
1494  if (TRACE_POSTGRESQL_LWLOCK_WAIT_DONE_ENABLED())
1495  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1497 
1498  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "awakened");
1499  }
1500  else
1501  {
1502  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "acquired, undoing queue");
1503 
1504  /*
1505  * Got lock in the second attempt, undo queueing. We need to treat
1506  * this as having successfully acquired the lock, otherwise we'd
1507  * not necessarily wake up people we've prevented from acquiring
1508  * the lock.
1509  */
1510  LWLockDequeueSelf(lock);
1511  }
1512  }
1513 
1514  /*
1515  * Fix the process wait semaphore's count for any absorbed wakeups.
1516  */
1517  while (extraWaits-- > 0)
1518  PGSemaphoreUnlock(proc->sem);
1519 
1520  if (mustwait)
1521  {
1522  /* Failed to get lock, so release interrupt holdoff */
1524  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "failed");
1525  if (TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_FAIL_ENABLED())
1526  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_FAIL(T_NAME(lock), mode);
1527  }
1528  else
1529  {
1530  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "succeeded");
1531  /* Add lock to list of locks held by this backend */
1534  if (TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_ENABLED())
1535  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT(T_NAME(lock), mode);
1536  }
1537 
1538  return !mustwait;
1539 }
#define RESUME_INTERRUPTS()
Definition: miscadmin.h:134

References Assert(), elog, ERROR, held_lwlocks, HOLD_INTERRUPTS, LWLockHandle::lock, LOG_LWDEBUG, LW_EXCLUSIVE, LW_SHARED, LW_WAIT_UNTIL_FREE, LWLockAttemptLock(), LWLockDequeueSelf(), LWLockQueueSelf(), LWLockReportWaitEnd(), LWLockReportWaitStart(), PGPROC::lwWaiting, MAX_BACKENDS, MAX_SIMUL_LWLOCKS, LWLockHandle::mode, mode, MyProc, num_held_lwlocks, pg_atomic_fetch_sub_u32(), PG_USED_FOR_ASSERTS_ONLY, PGSemaphoreLock(), PGSemaphoreUnlock(), PRINT_LWDEBUG, RESUME_INTERRUPTS, PGPROC::sem, and T_NAME.

Referenced by XLogFlush().

◆ LWLockConditionalAcquire()

bool LWLockConditionalAcquire ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1367 of file lwlock.c.

1368 {
1369  bool mustwait;
1370 
1372 
1373  PRINT_LWDEBUG("LWLockConditionalAcquire", lock, mode);
1374 
1375  /* Ensure we will have room to remember the lock */
1377  elog(ERROR, "too many LWLocks taken");
1378 
1379  /*
1380  * Lock out cancel/die interrupts until we exit the code section protected
1381  * by the LWLock. This ensures that interrupts will not interfere with
1382  * manipulations of data structures in shared memory.
1383  */
1384  HOLD_INTERRUPTS();
1385 
1386  /* Check for the lock */
1387  mustwait = LWLockAttemptLock(lock, mode);
1388 
1389  if (mustwait)
1390  {
1391  /* Failed to get lock, so release interrupt holdoff */
1393 
1394  LOG_LWDEBUG("LWLockConditionalAcquire", lock, "failed");
1395  if (TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_FAIL_ENABLED())
1396  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_FAIL(T_NAME(lock), mode);
1397  }
1398  else
1399  {
1400  /* Add lock to list of locks held by this backend */
1403  if (TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_ENABLED())
1404  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE(T_NAME(lock), mode);
1405  }
1406  return !mustwait;
1407 }

References AssertArg, elog, ERROR, held_lwlocks, HOLD_INTERRUPTS, LWLockHandle::lock, LOG_LWDEBUG, LW_EXCLUSIVE, LW_SHARED, LWLockAttemptLock(), MAX_SIMUL_LWLOCKS, LWLockHandle::mode, mode, num_held_lwlocks, PRINT_LWDEBUG, RESUME_INTERRUPTS, and T_NAME.

Referenced by BufferAlloc(), ConditionalLockBuffer(), pgstat_flush_wal(), pgstat_lock_entry(), pgstat_slru_flush(), ProcArrayEndTransaction(), SimpleLruWaitIO(), ss_report_location(), TransactionIdSetPageStatus(), and XLogNeedsFlush().

◆ LWLockHeldByMe()

◆ LWLockHeldByMeInMode()

◆ LWLockHeldCount()

int LWLockHeldCount ( void  )

Definition at line 1948 of file lwlock.c.

1949 {
1950  return num_held_lwlocks;
1951 }

References num_held_lwlocks.

Referenced by ShutdownPostgres().

◆ LWLockInitialize()

void LWLockInitialize ( LWLock lock,
int  tranche_id 
)

Definition at line 734 of file lwlock.c.

735 {
737 #ifdef LOCK_DEBUG
738  pg_atomic_init_u32(&lock->nwaiters, 0);
739 #endif
740  lock->tranche = tranche_id;
741  proclist_init(&lock->waiters);
742 }
static void pg_atomic_init_u32(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: atomics.h:223
static void proclist_init(proclist_head *list)
Definition: proclist.h:29
uint16 tranche
Definition: lwlock.h:33
proclist_head waiters
Definition: lwlock.h:35

References LW_FLAG_RELEASE_OK, pg_atomic_init_u32(), proclist_init(), LWLock::state, LWLock::tranche, and LWLock::waiters.

Referenced by apw_init_shmem(), create_internal(), dshash_create(), ExecAppendInitializeDSM(), ExecHashJoinInitializeDSM(), InitBufferPool(), InitializeLWLocks(), InitPredicateLocks(), InitProcGlobal(), pgstat_init_entry(), ReplicationOriginShmemInit(), ReplicationSlotsShmemInit(), SimpleLruInit(), StatsShmemInit(), sts_initialize(), tbm_prepare_shared_iterate(), and XLOGShmemInit().

◆ LWLockNewTrancheId()

int LWLockNewTrancheId ( void  )

Definition at line 626 of file lwlock.c.

627 {
628  int result;
629  int *LWLockCounter;
630 
631  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
633  result = (*LWLockCounter)++;
635 
636  return result;
637 }
slock_t * ShmemLock
Definition: shmem.c:88
#define SpinLockRelease(lock)
Definition: spin.h:64
#define SpinLockAcquire(lock)
Definition: spin.h:62

References MainLWLockArray, ShmemLock, SpinLockAcquire, and SpinLockRelease.

Referenced by apw_init_shmem(), and InitializeLWLocks().

◆ LWLockRegisterTranche()

void LWLockRegisterTranche ( int  tranche_id,
const char *  tranche_name 
)

Definition at line 650 of file lwlock.c.

651 {
652  /* This should only be called for user-defined tranches. */
653  if (tranche_id < LWTRANCHE_FIRST_USER_DEFINED)
654  return;
655 
656  /* Convert to array index. */
657  tranche_id -= LWTRANCHE_FIRST_USER_DEFINED;
658 
659  /* If necessary, create or enlarge array. */
660  if (tranche_id >= LWLockTrancheNamesAllocated)
661  {
662  int newalloc;
663 
664  newalloc = pg_nextpower2_32(Max(8, tranche_id + 1));
665 
666  if (LWLockTrancheNames == NULL)
667  LWLockTrancheNames = (const char **)
669  newalloc * sizeof(char *));
670  else
671  {
672  LWLockTrancheNames = (const char **)
673  repalloc(LWLockTrancheNames, newalloc * sizeof(char *));
675  0,
676  (newalloc - LWLockTrancheNamesAllocated) * sizeof(char *));
677  }
678  LWLockTrancheNamesAllocated = newalloc;
679  }
680 
681  LWLockTrancheNames[tranche_id] = tranche_name;
682 }
#define Max(x, y)
Definition: c.h:980
static int LWLockTrancheNamesAllocated
Definition: lwlock.c:198
static const char ** LWLockTrancheNames
Definition: lwlock.c:197
MemoryContext TopMemoryContext
Definition: mcxt.c:48
void * MemoryContextAllocZero(MemoryContext context, Size size)
Definition: mcxt.c:906
void * repalloc(void *pointer, Size size)
Definition: mcxt.c:1188
static uint32 pg_nextpower2_32(uint32 num)
Definition: pg_bitutils.h:140

References LWLockTrancheNames, LWLockTrancheNamesAllocated, LWTRANCHE_FIRST_USER_DEFINED, Max, MemoryContextAllocZero(), pg_nextpower2_32(), repalloc(), and TopMemoryContext.

Referenced by apw_init_shmem(), and CreateLWLocks().

◆ LWLockRelease()

void LWLockRelease ( LWLock lock)

Definition at line 1800 of file lwlock.c.

1801 {
1802  LWLockMode mode;
1803  uint32 oldstate;
1804  bool check_waiters;
1805  int i;
1806 
1807  /*
1808  * Remove lock from list of locks held. Usually, but not always, it will
1809  * be the latest-acquired lock; so search array backwards.
1810  */
1811  for (i = num_held_lwlocks; --i >= 0;)
1812  if (lock == held_lwlocks[i].lock)
1813  break;
1814 
1815  if (i < 0)
1816  elog(ERROR, "lock %s is not held", T_NAME(lock));
1817 
1818  mode = held_lwlocks[i].mode;
1819 
1820  num_held_lwlocks--;
1821  for (; i < num_held_lwlocks; i++)
1822  held_lwlocks[i] = held_lwlocks[i + 1];
1823 
1824  PRINT_LWDEBUG("LWLockRelease", lock, mode);
1825 
1826  /*
1827  * Release my hold on lock, after that it can immediately be acquired by
1828  * others, even if we still have to wakeup other waiters.
1829  */
1830  if (mode == LW_EXCLUSIVE)
1831  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_EXCLUSIVE);
1832  else
1833  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_SHARED);
1834 
1835  /* nobody else can have that kind of lock */
1836  Assert(!(oldstate & LW_VAL_EXCLUSIVE));
1837 
1838  if (TRACE_POSTGRESQL_LWLOCK_RELEASE_ENABLED())
1839  TRACE_POSTGRESQL_LWLOCK_RELEASE(T_NAME(lock));
1840 
1841  /*
1842  * We're still waiting for backends to get scheduled, don't wake them up
1843  * again.
1844  */
1845  if ((oldstate & (LW_FLAG_HAS_WAITERS | LW_FLAG_RELEASE_OK)) ==
1847  (oldstate & LW_LOCK_MASK) == 0)
1848  check_waiters = true;
1849  else
1850  check_waiters = false;
1851 
1852  /*
1853  * As waking up waiters requires the spinlock to be acquired, only do so
1854  * if necessary.
1855  */
1856  if (check_waiters)
1857  {
1858  /* XXX: remove before commit? */
1859  LOG_LWDEBUG("LWLockRelease", lock, "releasing waiters");
1860  LWLockWakeup(lock);
1861  }
1862 
1863  /*
1864  * Now okay to allow cancel/die interrupts.
1865  */
1867 }
static uint32 pg_atomic_sub_fetch_u32(volatile pg_atomic_uint32 *ptr, int32 sub_)
Definition: atomics.h:401
static void LWLockWakeup(LWLock *lock)
Definition: lwlock.c:951
#define LW_VAL_SHARED
Definition: lwlock.c:105
#define LW_LOCK_MASK
Definition: lwlock.c:107
#define LW_FLAG_HAS_WAITERS
Definition: lwlock.c:100

References Assert(), elog, ERROR, held_lwlocks, i, LOG_LWDEBUG, LW_EXCLUSIVE, LW_FLAG_HAS_WAITERS, LW_FLAG_RELEASE_OK, LW_LOCK_MASK, LW_VAL_EXCLUSIVE, LW_VAL_SHARED, LWLockWakeup(), LWLockHandle::mode, mode, num_held_lwlocks, pg_atomic_sub_fetch_u32(), PRINT_LWDEBUG, RESUME_INTERRUPTS, LWLock::state, and T_NAME.

Referenced by _bt_end_vacuum(), _bt_start_vacuum(), _bt_vacuum_cycleid(), AbsorbSyncRequests(), ActivateCommitTs(), AdvanceNextFullTransactionIdPastXid(), AdvanceOldestClogXid(), AdvanceOldestCommitTsXid(), AdvanceXLInsertBuffer(), alloc_object(), AlterSystemSetConfigFile(), ApplyLauncherMain(), apw_detach_shmem(), apw_dump_now(), apw_init_shmem(), apw_load_buffers(), asyncQueueAddEntries(), asyncQueueAdvanceTail(), asyncQueueReadAllNotifications(), asyncQueueUnregister(), AtAbort_Twophase(), AtPrepare_PredicateLocks(), attach_internal(), autoprewarm_main(), autoprewarm_start_worker(), AutoVacLauncherMain(), AutoVacuumRequestWork(), AutoVacWorkerMain(), BackendIdGetProc(), BackendIdGetTransactionIds(), BackendPidGetProc(), BackendXidGetPid(), BecomeLockGroupLeader(), BecomeLockGroupMember(), BootStrapCLOG(), BootStrapMultiXact(), BootStrapSUBTRANS(), BootStrapXLOG(), BufferAlloc(), CancelDBBackends(), check_for_freed_segments(), CheckDeadLock(), CheckForSerializableConflictOut(), CheckPointPredicate(), CheckPointRelationMap(), CheckPointReplicationOrigin(), CheckPointReplicationSlots(), CheckPointTwoPhase(), CheckTableForSerializableConflictIn(), CheckTargetForConflictsIn(), choose_next_subplan_for_leader(), choose_next_subplan_for_worker(), CleanupInvalidationState(), ClearOldPredicateLocks(), clog_redo(), commit_ts_redo(), ComputeXidHorizons(), copy_replication_slot(), CountDBBackends(), CountDBConnections(), CountOtherDBBackends(), CountUserBackends(), CreateCheckPoint(), CreateEndOfRecoveryRecord(), CreateInitDecodingContext(), CreatePredicateLock(), CreateRestartPoint(), DeactivateCommitTs(), DeleteChildTargetLocks(), DeleteLockTarget(), destroy_superblock(), do_autovacuum(), do_pg_backup_start(), do_pg_backup_stop(), do_start_worker(), DropAllPredicateLocksFromTable(), DropSubscription(), DropTableSpace(), dsa_allocate_extended(), dsa_dump(), dsa_free(), dsa_pin(), dsa_release_in_place(), dsa_set_size_limit(), dsa_trim(), dsa_unpin(), dshash_delete_entry(), dshash_delete_key(), dshash_dump(), dshash_find(), dshash_find_or_insert(), dshash_release_lock(), dshash_seq_next(), dshash_seq_term(), dsm_attach(), dsm_create(), dsm_detach(), dsm_pin_segment(), dsm_unpin_segment(), ensure_active_superblock(), entry_reset(), Exec_ListenPreCommit(), ExecParallelHashMergeCounters(), ExecParallelHashPopChunkQueue(), ExecParallelHashTupleAlloc(), ExecParallelHashTuplePrealloc(), ExpireAllKnownAssignedTransactionIds(), ExpireOldKnownAssignedTransactionIds(), ExpireTreeKnownAssignedTransactionIds(), ExtendCLOG(), ExtendCommitTs(), ExtendMultiXactMember(), ExtendMultiXactOffset(), ExtendSUBTRANS(), FastPathGetRelationLockEntry(), FastPathTransferRelationLocks(), find_multixact_start(), FindAndDropRelFileNodeBuffers(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLockConflicts(), GetLockStatusData(), GetMultiXactIdMembers(), GetNewMultiXactId(), GetNewObjectId(), GetNewTransactionId(), GetOldestActiveTransactionId(), GetOldestMultiXactId(), GetOldestRestartPoint(), GetOldestSafeDecodingTransactionId(), GetOldSnapshotFromTimeMapping(), GetOldSnapshotTimeMapping(), GetPredicateLockStatusData(), GetPreparedTransactionList(), GetRunningTransactionLocks(), GetSafeSnapshot(), GetSafeSnapshotBlockingPids(), GetSerializableTransactionSnapshotInt(), GetSnapshotData(), GetVirtualXIDsDelayingChkpt(), HandleAutoVacLauncherInterrupts(), HaveVirtualXIDsDelayingChkpt(), InstallXLogFileSegment(), InvalidateBuffer(), InvalidateObsoleteReplicationSlots(), InvalidatePossiblyObsoleteSlot(), IsInstallXLogFileSegmentActive(), KnownAssignedXidsAdd(), KnownAssignedXidsReset(), lock_twophase_recover(), LockAcquireExtended(), LockBuffer(), LockErrorCleanup(), LockGXact(), LockHasWaiters(), LockRefindAndRelease(), LockRelease(), LockReleaseAll(), LockWaiterCount(), logicalrep_worker_attach(), logicalrep_worker_detach(), logicalrep_worker_launch(), logicalrep_worker_stop(), logicalrep_worker_wakeup(), LogStandbySnapshot(), LookupGXact(), LWLockReleaseAll(), LWLockReleaseClearVar(), MaintainOldSnapshotTimeMapping(), MarkAsPrepared(), MarkAsPreparing(), MaybeExtendOffsetSlru(), multixact_redo(), MultiXactAdvanceNextMXact(), MultiXactGetCheckptMulti(), MultiXactIdSetOldestMember(), MultiXactIdSetOldestVisible(), MultiXactSetNextMXact(), OnConflict_CheckForSerializationFailure(), PageIsPredicateLocked(), perform_relmap_update(), pg_get_replication_slots(), pg_get_shmem_allocations(), pg_notification_queue_usage(), pg_show_replication_origin_status(), pg_stat_get_subscription(), pg_stat_statements_internal(), pg_xact_status(), pgss_shmem_startup(), pgss_store(), pgstat_archiver_reset_all_cb(), pgstat_archiver_snapshot_cb(), pgstat_bgwriter_reset_all_cb(), pgstat_bgwriter_snapshot_cb(), pgstat_checkpointer_reset_all_cb(), pgstat_checkpointer_snapshot_cb(), pgstat_flush_wal(), pgstat_reset_matching_entries(), pgstat_reset_slru_counter_internal(), pgstat_slru_flush(), pgstat_slru_snapshot_cb(), pgstat_unlock_entry(), pgstat_wal_reset_all_cb(), pgstat_wal_snapshot_cb(), PostPrepare_Locks(), PostPrepare_MultiXact(), PostPrepare_Twophase(), PreCommit_CheckForSerializationFailure(), PreCommit_Notify(), predicatelock_twophase_recover(), PredicateLockPageSplit(), PredicateLockTwoPhaseFinish(), PrefetchSharedBuffer(), PrescanPreparedTransactions(), ProcArrayAdd(), ProcArrayApplyRecoveryInfo(), ProcArrayApplyXidAssignment(), ProcArrayClearTransaction(), ProcArrayEndTransaction(), ProcArrayGetReplicationSlotXmin(), ProcArrayGroupClearXid(), ProcArrayInstallImportedXmin(), ProcArrayInstallRestoredXmin(), ProcArrayRemove(), ProcArraySetReplicationSlotXmin(), process_syncing_tables_for_apply(), ProcKill(), ProcSleep(), ReachedEndOfBackup(), read_relmap_file(), ReadMultiXactCounts(), ReadMultiXactIdRange(), ReadNextFullTransactionId(), ReadNextMultiXactId(), ReadReplicationSlot(), RecordNewMultiXact(), RecoverPreparedTransactions(), RegisterDynamicBackgroundWorker(), RegisterPredicateLockingXid(), RelationCacheInitFilePostInvalidate(), ReleaseOneSerializableXact(), ReleasePredicateLocks(), relmap_redo(), RemoveScratchTarget(), ReplicationOriginExitCleanup(), ReplicationSlotAcquire(), ReplicationSlotCleanup(), ReplicationSlotCreate(), ReplicationSlotDropPtr(), ReplicationSlotRelease(), ReplicationSlotsComputeLogicalRestartLSN(), ReplicationSlotsComputeRequiredLSN(), ReplicationSlotsComputeRequiredXmin(), ReplicationSlotsCountDBSlots(), ReplicationSlotsDropDBSlots(), replorigin_advance(), replorigin_drop_guts(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), resize(), RestoreScratchTarget(), restoreTwoPhaseData(), SaveSlotToPath(), SearchNamedReplicationSlot(), SerialAdd(), SerialGetMinConflictCommitSeqNo(), SerialSetActiveSerXmin(), set_indexsafe_procflags(), SetCommitTsLimit(), SetInstallXLogFileSegmentActive(), SetMultiXactIdLimit(), SetNextObjectId(), SetOffsetVacuumLimit(), SetTransactionIdLimit(), SetXidCommitTsInPage(), SharedInvalBackendInit(), ShmemInitStruct(), SICleanupQueue(), SIGetDataEntries(), SignalBackends(), SignalVirtualTransaction(), SIInsertDataEntries(), SimpleLruReadPage(), SimpleLruReadPage_ReadOnly(), SimpleLruTruncate(), SimpleLruWaitIO(), SimpleLruWriteAll(), SlruDeleteSegment(), SlruInternalWritePage(), SnapBuildInitialSnapshot(), ss_get_location(), ss_report_location(), StandbyRecoverPreparedTransactions(), StartupCLOG(), StartupDecodingContext(), StartupSUBTRANS(), StartupXLOG(), sts_parallel_scan_next(), SubTransGetParent(), SubTransSetParent(), SummarizeOldestCommittedSxact(), SwitchIntoArchiveRecovery(), SyncOneBuffer(), SyncRepCancelWait(), SyncRepCleanupAtProcExit(), SyncRepReleaseWaiters(), SyncRepUpdateSyncStandbysDefined(), SyncRepWaitForLSN(), TablespaceCreateDbspace(), tbm_shared_iterate(), TerminateBackgroundWorker(), TerminateOtherDBBackends(), TransactionGroupUpdateXidStatus(), TransactionIdGetCommitTsData(), TransactionIdGetStatus(), TransactionIdIsActive(), TransactionIdIsInProgress(), TransactionIdSetPageStatus(), TransactionTreeSetCommitTsData(), TransferPredicateLocksToNewTarget(), TrimCLOG(), TrimMultiXact(), TruncateMultiXact(), TwoPhaseGetGXact(), TwoPhaseGetXidByVirtualXID(), update_cached_xid_range(), UpdateMinRecoveryPoint(), vac_truncate_clog(), vacuum_rel(), VirtualXactLock(), VirtualXactLockTableCleanup(), VirtualXactLockTableInsert(), wait_for_relation_state_change(), wait_for_worker_state_change(), WaitForReplicationWorkerAttach(), WaitOnLock(), write_relcache_init_file(), xact_redo(), XidCacheRemoveRunningXids(), xlog_redo(), XLogBackgroundFlush(), XLogFlush(), XLogNeedsFlush(), XLogReportParameters(), and XLogShutdownWalRcv().

◆ LWLockReleaseAll()

void LWLockReleaseAll ( void  )

Definition at line 1899 of file lwlock.c.

1900 {
1901  while (num_held_lwlocks > 0)
1902  {
1903  HOLD_INTERRUPTS(); /* match the upcoming RESUME_INTERRUPTS */
1904 
1906  }
1907 }
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1800

References held_lwlocks, HOLD_INTERRUPTS, LWLockRelease(), and num_held_lwlocks.

Referenced by AbortSubTransaction(), AbortTransaction(), AutoVacLauncherMain(), AuxiliaryProcKill(), BackgroundWriterMain(), CheckpointerMain(), ProcKill(), ShutdownAuxiliaryProcess(), WalSndErrorCleanup(), and WalWriterMain().

◆ LWLockReleaseClearVar()

void LWLockReleaseClearVar ( LWLock lock,
uint64 *  valptr,
uint64  val 
)

Definition at line 1873 of file lwlock.c.

1874 {
1875  LWLockWaitListLock(lock);
1876 
1877  /*
1878  * Set the variable's value before releasing the lock, that prevents race
1879  * a race condition wherein a new locker acquires the lock, but hasn't yet
1880  * set the variables value.
1881  */
1882  *valptr = val;
1883  LWLockWaitListUnlock(lock);
1884 
1885  LWLockRelease(lock);
1886 }
long val
Definition: informix.c:664
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:886
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:938

References LWLockRelease(), LWLockWaitListLock(), LWLockWaitListUnlock(), and val.

Referenced by WALInsertLockRelease().

◆ LWLockShmemSize()

Size LWLockShmemSize ( void  )

Definition at line 437 of file lwlock.c.

438 {
439  Size size;
440  int i;
441  int numLocks = NUM_FIXED_LWLOCKS;
442 
443  /* Calculate total number of locks needed in the main array. */
444  numLocks += NumLWLocksForNamedTranches();
445 
446  /* Space for the LWLock array. */
447  size = mul_size(numLocks, sizeof(LWLockPadded));
448 
449  /* Space for dynamic allocation counter, plus room for alignment. */
450  size = add_size(size, sizeof(int) + LWLOCK_PADDED_SIZE);
451 
452  /* space for named tranches. */
454 
455  /* space for name of each tranche. */
456  for (i = 0; i < NamedLWLockTrancheRequests; i++)
457  size = add_size(size, strlen(NamedLWLockTrancheRequestArray[i].tranche_name) + 1);
458 
459  return size;
460 }
static int NumLWLocksForNamedTranches(void)
Definition: lwlock.c:422
Size add_size(Size s1, Size s2)
Definition: shmem.c:502
Size mul_size(Size s1, Size s2)
Definition: shmem.c:519

References add_size(), i, LWLOCK_PADDED_SIZE, mul_size(), NamedLWLockTrancheRequestArray, NamedLWLockTrancheRequests, NUM_FIXED_LWLOCKS, and NumLWLocksForNamedTranches().

Referenced by CalculateShmemSize(), and CreateLWLocks().

◆ LWLockUpdateVar()

void LWLockUpdateVar ( LWLock lock,
uint64 *  valptr,
uint64  value 
)

Definition at line 1746 of file lwlock.c.

1747 {
1748  proclist_head wakeup;
1749  proclist_mutable_iter iter;
1750 
1751  PRINT_LWDEBUG("LWLockUpdateVar", lock, LW_EXCLUSIVE);
1752 
1753  proclist_init(&wakeup);
1754 
1755  LWLockWaitListLock(lock);
1756 
1758 
1759  /* Update the lock's value */
1760  *valptr = val;
1761 
1762  /*
1763  * See if there are any LW_WAIT_UNTIL_FREE waiters that need to be woken
1764  * up. They are always in the front of the queue.
1765  */
1766  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
1767  {
1768  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1769 
1770  if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
1771  break;
1772 
1773  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
1774  proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
1775  }
1776 
1777  /* We are done updating shared state of the lock itself. */
1778  LWLockWaitListUnlock(lock);
1779 
1780  /*
1781  * Awaken any waiters I removed from the queue.
1782  */
1783  proclist_foreach_modify(iter, &wakeup, lwWaitLink)
1784  {
1785  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1786 
1787  proclist_delete(&wakeup, iter.cur, lwWaitLink);
1788  /* check comment in LWLockWakeup() about this barrier */
1789  pg_write_barrier();
1790  waiter->lwWaiting = false;
1791  PGSemaphoreUnlock(waiter->sem);
1792  }
1793 }
#define pg_write_barrier()
Definition: atomics.h:159
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:241
#define GetPGProcByNumber(n)
Definition: proc.h:402
#define proclist_delete(list, procno, link_member)
Definition: proclist.h:187
#define proclist_push_tail(list, procno, link_member)
Definition: proclist.h:191
#define proclist_foreach_modify(iter, lhead, link_member)
Definition: proclist.h:206
uint8 lwWaitMode
Definition: proc.h:209

References Assert(), proclist_mutable_iter::cur, GetPGProcByNumber, LW_EXCLUSIVE, LW_VAL_EXCLUSIVE, LW_WAIT_UNTIL_FREE, LWLockWaitListLock(), LWLockWaitListUnlock(), PGPROC::lwWaiting, PGPROC::lwWaitMode, pg_atomic_read_u32(), pg_write_barrier, PGSemaphoreUnlock(), PRINT_LWDEBUG, proclist_delete, proclist_foreach_modify, proclist_init(), proclist_push_tail, PGPROC::sem, LWLock::state, val, and LWLock::waiters.

Referenced by WALInsertLockAcquireExclusive(), and WALInsertLockUpdateInsertingAt().

◆ LWLockWaitForVar()

bool LWLockWaitForVar ( LWLock lock,
uint64 *  valptr,
uint64  oldval,
uint64 *  newval 
)

Definition at line 1611 of file lwlock.c.

1612 {
1613  PGPROC *proc = MyProc;
1614  int extraWaits = 0;
1615  bool result = false;
1616 #ifdef LWLOCK_STATS
1617  lwlock_stats *lwstats;
1618 
1619  lwstats = get_lwlock_stats_entry(lock);
1620 #endif
1621 
1622  PRINT_LWDEBUG("LWLockWaitForVar", lock, LW_WAIT_UNTIL_FREE);
1623 
1624  /*
1625  * Lock out cancel/die interrupts while we sleep on the lock. There is no
1626  * cleanup mechanism to remove us from the wait queue if we got
1627  * interrupted.
1628  */
1629  HOLD_INTERRUPTS();
1630 
1631  /*
1632  * Loop here to check the lock's status after each time we are signaled.
1633  */
1634  for (;;)
1635  {
1636  bool mustwait;
1637 
1638  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1639  &result);
1640 
1641  if (!mustwait)
1642  break; /* the lock was free or value didn't match */
1643 
1644  /*
1645  * Add myself to wait queue. Note that this is racy, somebody else
1646  * could wakeup before we're finished queuing. NB: We're using nearly
1647  * the same twice-in-a-row lock acquisition protocol as
1648  * LWLockAcquire(). Check its comments for details. The only
1649  * difference is that we also have to check the variable's values when
1650  * checking the state of the lock.
1651  */
1653 
1654  /*
1655  * Set RELEASE_OK flag, to make sure we get woken up as soon as the
1656  * lock is released.
1657  */
1659 
1660  /*
1661  * We're now guaranteed to be woken up if necessary. Recheck the lock
1662  * and variables state.
1663  */
1664  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1665  &result);
1666 
1667  /* Ok, no conflict after we queued ourselves. Undo queueing. */
1668  if (!mustwait)
1669  {
1670  LOG_LWDEBUG("LWLockWaitForVar", lock, "free, undoing queue");
1671 
1672  LWLockDequeueSelf(lock);
1673  break;
1674  }
1675 
1676  /*
1677  * Wait until awakened.
1678  *
1679  * It is possible that we get awakened for a reason other than being
1680  * signaled by LWLockRelease. If so, loop back and wait again. Once
1681  * we've gotten the LWLock, re-increment the sema by the number of
1682  * additional signals received.
1683  */
1684  LOG_LWDEBUG("LWLockWaitForVar", lock, "waiting");
1685 
1686 #ifdef LWLOCK_STATS
1687  lwstats->block_count++;
1688 #endif
1689 
1690  LWLockReportWaitStart(lock);
1691  if (TRACE_POSTGRESQL_LWLOCK_WAIT_START_ENABLED())
1692  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), LW_EXCLUSIVE);
1693 
1694  for (;;)
1695  {
1696  PGSemaphoreLock(proc->sem);
1697  if (!proc->lwWaiting)
1698  break;
1699  extraWaits++;
1700  }
1701 
1702 #ifdef LOCK_DEBUG
1703  {
1704  /* not waiting anymore */
1705  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1706 
1707  Assert(nwaiters < MAX_BACKENDS);
1708  }
1709 #endif
1710 
1711  if (TRACE_POSTGRESQL_LWLOCK_WAIT_DONE_ENABLED())
1712  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), LW_EXCLUSIVE);
1714 
1715  LOG_LWDEBUG("LWLockWaitForVar", lock, "awakened");
1716 
1717  /* Now loop back and check the status of the lock again. */
1718  }
1719 
1720  /*
1721  * Fix the process wait semaphore's count for any absorbed wakeups.
1722  */
1723  while (extraWaits-- > 0)
1724  PGSemaphoreUnlock(proc->sem);
1725 
1726  /*
1727  * Now okay to allow cancel/die interrupts.
1728  */
1730 
1731  return result;
1732 }
#define newval
static bool LWLockConflictsWithVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval, bool *result)
Definition: lwlock.c:1551

References Assert(), HOLD_INTERRUPTS, LOG_LWDEBUG, LW_EXCLUSIVE, LW_FLAG_RELEASE_OK, LW_WAIT_UNTIL_FREE, LWLockConflictsWithVar(), LWLockDequeueSelf(), LWLockQueueSelf(), LWLockReportWaitEnd(), LWLockReportWaitStart(), PGPROC::lwWaiting, MAX_BACKENDS, MyProc, newval, pg_atomic_fetch_or_u32(), pg_atomic_fetch_sub_u32(), PG_USED_FOR_ASSERTS_ONLY, PGSemaphoreLock(), PGSemaphoreUnlock(), PRINT_LWDEBUG, RESUME_INTERRUPTS, PGPROC::sem, LWLock::state, and T_NAME.

Referenced by WaitXLogInsertionsToFinish().

◆ RequestNamedLWLockTranche()

void RequestNamedLWLockTranche ( const char *  tranche_name,
int  num_lwlocks 
)

Definition at line 697 of file lwlock.c.

698 {
699  NamedLWLockTrancheRequest *request;
700 
702  elog(FATAL, "cannot request additional LWLocks outside shmem_request_hook");
703 
704  if (NamedLWLockTrancheRequestArray == NULL)
705  {
710  * sizeof(NamedLWLockTrancheRequest));
711  }
712 
714  {
716 
719  i * sizeof(NamedLWLockTrancheRequest));
721  }
722 
724  Assert(strlen(tranche_name) + 1 <= NAMEDATALEN);
725  strlcpy(request->tranche_name, tranche_name, NAMEDATALEN);
726  request->num_lwlocks = num_lwlocks;
728 }
#define FATAL
Definition: elog.h:35
static int NamedLWLockTrancheRequestsAllocated
Definition: lwlock.c:233
void * MemoryContextAlloc(MemoryContext context, Size size)
Definition: mcxt.c:863
bool process_shmem_requests_in_progress
Definition: miscinit.c:1622
#define NAMEDATALEN
size_t strlcpy(char *dst, const char *src, size_t siz)
Definition: strlcpy.c:45
char tranche_name[NAMEDATALEN]
Definition: lwlock.c:228

References Assert(), elog, FATAL, i, MemoryContextAlloc(), NAMEDATALEN, NamedLWLockTrancheRequestArray, NamedLWLockTrancheRequests, NamedLWLockTrancheRequestsAllocated, NamedLWLockTrancheRequest::num_lwlocks, pg_nextpower2_32(), process_shmem_requests_in_progress, repalloc(), strlcpy(), TopMemoryContext, and NamedLWLockTrancheRequest::tranche_name.

Referenced by pgss_shmem_request().

Variable Documentation

◆ MainLWLockArray

PGDLLIMPORT LWLockPadded* MainLWLockArray
extern

◆ NamedLWLockTrancheArray

PGDLLIMPORT NamedLWLockTranche* NamedLWLockTrancheArray
extern

Definition at line 244 of file lwlock.c.

Referenced by CreateLWLocks(), and InitializeLWLocks().

◆ NamedLWLockTrancheRequests