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

Enumerations

enum  LWLockWaitState { LW_WS_NOT_WAITING , LW_WS_WAITING , LW_WS_PENDING_WAKEUP }
 
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_LAUNCHER_DSA ,
  LWTRANCHE_LAUNCHER_HASH , LWTRANCHE_FIRST_USER_DEFINED
}
 

Functions

 StaticAssertDecl (sizeof(LWLock)<=LWLOCK_PADDED_SIZE, "Miscalculated LWLock padding")
 
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 LWLockAnyHeldByMe (LWLock *lock, int nlocks, size_t stride)
 
bool LWLockHeldByMeInMode (LWLock *lock, LWLockMode mode)
 
bool LWLockWaitForVar (LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval)
 
void LWLockUpdateVar (LWLock *lock, uint64 *valptr, uint64 val)
 
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 105 of file lwlock.h.

◆ LOCK_MANAGER_LWLOCK_OFFSET

#define LOCK_MANAGER_LWLOCK_OFFSET    (BUFFER_MAPPING_LWLOCK_OFFSET + NUM_BUFFER_PARTITIONS)

Definition at line 106 of file lwlock.h.

◆ LOG2_NUM_LOCK_PARTITIONS

#define LOG2_NUM_LOCK_PARTITIONS   4

Definition at line 97 of file lwlock.h.

◆ LOG2_NUM_PREDICATELOCK_PARTITIONS

#define LOG2_NUM_PREDICATELOCK_PARTITIONS   4

Definition at line 101 of file lwlock.h.

◆ LWLOCK_PADDED_SIZE

#define LWLOCK_PADDED_SIZE   PG_CACHE_LINE_SIZE

Definition at line 60 of file lwlock.h.

◆ NUM_BUFFER_PARTITIONS

#define NUM_BUFFER_PARTITIONS   128

Definition at line 94 of file lwlock.h.

◆ NUM_FIXED_LWLOCKS

Definition at line 110 of file lwlock.h.

◆ NUM_LOCK_PARTITIONS

#define NUM_LOCK_PARTITIONS   (1 << LOG2_NUM_LOCK_PARTITIONS)

Definition at line 98 of file lwlock.h.

◆ NUM_PREDICATELOCK_PARTITIONS

#define NUM_PREDICATELOCK_PARTITIONS   (1 << LOG2_NUM_PREDICATELOCK_PARTITIONS)

Definition at line 102 of file lwlock.h.

◆ PREDICATELOCK_MANAGER_LWLOCK_OFFSET

#define PREDICATELOCK_MANAGER_LWLOCK_OFFSET    (LOCK_MANAGER_LWLOCK_OFFSET + NUM_LOCK_PARTITIONS)

Definition at line 108 of file lwlock.h.

Typedef Documentation

◆ BuiltinTrancheIds

◆ LWLock

typedef struct LWLock LWLock

◆ LWLockId

typedef LWLock* LWLockId

Definition at line 217 of file lwlock.h.

◆ LWLockMode

typedef enum LWLockMode LWLockMode

◆ LWLockPadded

typedef union LWLockPadded LWLockPadded

◆ LWLockWaitState

◆ 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_LAUNCHER_DSA 
LWTRANCHE_LAUNCHER_HASH 
LWTRANCHE_FIRST_USER_DEFINED 

Definition at line 178 of file lwlock.h.

179 {
180  LWTRANCHE_XACT_BUFFER = NUM_INDIVIDUAL_LWLOCKS,
BuiltinTrancheIds
Definition: lwlock.h:179
@ LWTRANCHE_FIRST_USER_DEFINED
Definition: lwlock.h:209
@ LWTRANCHE_SHARED_TIDBITMAP
Definition: lwlock.h:201
@ LWTRANCHE_PER_SESSION_DSA
Definition: lwlock.h:197
@ LWTRANCHE_PARALLEL_QUERY_DSA
Definition: lwlock.h:196
@ LWTRANCHE_COMMITTS_BUFFER
Definition: lwlock.h:181
@ LWTRANCHE_PGSTATS_HASH
Definition: lwlock.h:205
@ LWTRANCHE_SUBTRANS_BUFFER
Definition: lwlock.h:182
@ LWTRANCHE_PER_SESSION_RECORD_TYPMOD
Definition: lwlock.h:199
@ LWTRANCHE_LAUNCHER_HASH
Definition: lwlock.h:208
@ LWTRANCHE_XACT_BUFFER
Definition: lwlock.h:180
@ LWTRANCHE_REPLICATION_ORIGIN_STATE
Definition: lwlock.h:189
@ LWTRANCHE_PARALLEL_APPEND
Definition: lwlock.h:202
@ LWTRANCHE_REPLICATION_SLOT_IO
Definition: lwlock.h:190
@ LWTRANCHE_BUFFER_CONTENT
Definition: lwlock.h:188
@ LWTRANCHE_MULTIXACTMEMBER_BUFFER
Definition: lwlock.h:184
@ LWTRANCHE_NOTIFY_BUFFER
Definition: lwlock.h:185
@ LWTRANCHE_PER_SESSION_RECORD_TYPE
Definition: lwlock.h:198
@ LWTRANCHE_PREDICATE_LOCK_MANAGER
Definition: lwlock.h:194
@ LWTRANCHE_BUFFER_MAPPING
Definition: lwlock.h:192
@ LWTRANCHE_SERIAL_BUFFER
Definition: lwlock.h:186
@ LWTRANCHE_LAUNCHER_DSA
Definition: lwlock.h:207
@ LWTRANCHE_PGSTATS_DSA
Definition: lwlock.h:204
@ LWTRANCHE_PARALLEL_HASH_JOIN
Definition: lwlock.h:195
@ LWTRANCHE_PGSTATS_DATA
Definition: lwlock.h:206
@ LWTRANCHE_PER_XACT_PREDICATE_LIST
Definition: lwlock.h:203
@ LWTRANCHE_MULTIXACTOFFSET_BUFFER
Definition: lwlock.h:183
@ LWTRANCHE_WAL_INSERT
Definition: lwlock.h:187
@ LWTRANCHE_LOCK_MANAGER
Definition: lwlock.h:193
@ LWTRANCHE_SHARED_TUPLESTORE
Definition: lwlock.h:200
@ LWTRANCHE_LOCK_FASTPATH
Definition: lwlock.h:191

◆ LWLockMode

enum LWLockMode
Enumerator
LW_EXCLUSIVE 
LW_SHARED 
LW_WAIT_UNTIL_FREE 

Definition at line 113 of file lwlock.h.

114 {
115  LW_EXCLUSIVE,
116  LW_SHARED,
117  LW_WAIT_UNTIL_FREE /* A special mode used in PGPROC->lwWaitMode,
118  * when waiting for lock to become free. Not
119  * to be used as LWLockAcquire argument */
120 } LWLockMode;
LWLockMode
Definition: lwlock.h:114
@ LW_SHARED
Definition: lwlock.h:116
@ LW_WAIT_UNTIL_FREE
Definition: lwlock.h:117
@ LW_EXCLUSIVE
Definition: lwlock.h:115

◆ LWLockWaitState

Enumerator
LW_WS_NOT_WAITING 
LW_WS_WAITING 
LW_WS_PENDING_WAKEUP 

Definition at line 27 of file lwlock.h.

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 */
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

Function Documentation

◆ CreateLWLocks()

void CreateLWLocks ( void  )

Definition at line 474 of file lwlock.c.

475 {
476  if (!IsUnderPostmaster)
477  {
478  Size spaceLocks = LWLockShmemSize();
479  int *LWLockCounter;
480  char *ptr;
481 
482  /* Allocate space */
483  ptr = (char *) ShmemAlloc(spaceLocks);
484 
485  /* Leave room for dynamic allocation of tranches */
486  ptr += sizeof(int);
487 
488  /* Ensure desired alignment of LWLock array */
489  ptr += LWLOCK_PADDED_SIZE - ((uintptr_t) ptr) % LWLOCK_PADDED_SIZE;
490 
491  MainLWLockArray = (LWLockPadded *) ptr;
492 
493  /*
494  * Initialize the dynamic-allocation counter for tranches, which is
495  * stored just before the first LWLock.
496  */
497  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
498  *LWLockCounter = LWTRANCHE_FIRST_USER_DEFINED;
499 
500  /* Initialize all LWLocks */
502  }
503 
504  /* Register named extension LWLock tranches in the current process. */
505  for (int i = 0; i < NamedLWLockTrancheRequests; i++)
507  NamedLWLockTrancheArray[i].trancheName);
508 }
size_t Size
Definition: c.h:589
bool IsUnderPostmaster
Definition: globals.c:113
int i
Definition: isn.c:73
NamedLWLockTranche * NamedLWLockTrancheArray
Definition: lwlock.c:251
void LWLockRegisterTranche(int tranche_id, const char *tranche_name)
Definition: lwlock.c:651
int NamedLWLockTrancheRequests
Definition: lwlock.c:248
static void InitializeLWLocks(void)
Definition: lwlock.c:514
LWLockPadded * MainLWLockArray
Definition: lwlock.c:212
Size LWLockShmemSize(void)
Definition: lwlock.c:444
#define LWLOCK_PADDED_SIZE
Definition: lwlock.h:60
void * ShmemAlloc(Size size)
Definition: shmem.c:161

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

Referenced by CreateSharedMemoryAndSemaphores().

◆ GetLWLockIdentifier()

const char* GetLWLockIdentifier ( uint32  classId,
uint16  eventId 
)

Definition at line 794 of file lwlock.c.

795 {
796  Assert(classId == PG_WAIT_LWLOCK);
797  /* The event IDs are just tranche numbers. */
798  return GetLWTrancheName(eventId);
799 }
Assert(fmt[strlen(fmt) - 1] !='\n')
static const char * GetLWTrancheName(uint16 trancheId)
Definition: lwlock.c:766
#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 597 of file lwlock.c.

598 {
599  int lock_pos;
600  int i;
601 
602  /*
603  * Obtain the position of base address of LWLock belonging to requested
604  * tranche_name in MainLWLockArray. LWLocks for named tranches are placed
605  * in MainLWLockArray after fixed locks.
606  */
607  lock_pos = NUM_FIXED_LWLOCKS;
608  for (i = 0; i < NamedLWLockTrancheRequests; i++)
609  {
610  if (strcmp(NamedLWLockTrancheRequestArray[i].tranche_name,
611  tranche_name) == 0)
612  return &MainLWLockArray[lock_pos];
613 
615  }
616 
617  elog(ERROR, "requested tranche is not registered");
618 
619  /* just to keep compiler quiet */
620  return NULL;
621 }
#define ERROR
Definition: elog.h:39
static NamedLWLockTrancheRequest * NamedLWLockTrancheRequestArray
Definition: lwlock.c:239
#define NUM_FIXED_LWLOCKS
Definition: lwlock.h:110

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 581 of file lwlock.c.

582 {
583 #ifdef LWLOCK_STATS
584  init_lwlock_stats();
585 #endif
586 }

Referenced by InitProcess().

◆ LWLockAcquire()

bool LWLockAcquire ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1195 of file lwlock.c.

1196 {
1197  PGPROC *proc = MyProc;
1198  bool result = true;
1199  int extraWaits = 0;
1200 #ifdef LWLOCK_STATS
1201  lwlock_stats *lwstats;
1202 
1203  lwstats = get_lwlock_stats_entry(lock);
1204 #endif
1205 
1207 
1208  PRINT_LWDEBUG("LWLockAcquire", lock, mode);
1209 
1210 #ifdef LWLOCK_STATS
1211  /* Count lock acquisition attempts */
1212  if (mode == LW_EXCLUSIVE)
1213  lwstats->ex_acquire_count++;
1214  else
1215  lwstats->sh_acquire_count++;
1216 #endif /* LWLOCK_STATS */
1217 
1218  /*
1219  * We can't wait if we haven't got a PGPROC. This should only occur
1220  * during bootstrap or shared memory initialization. Put an Assert here
1221  * to catch unsafe coding practices.
1222  */
1223  Assert(!(proc == NULL && IsUnderPostmaster));
1224 
1225  /* Ensure we will have room to remember the lock */
1227  elog(ERROR, "too many LWLocks taken");
1228 
1229  /*
1230  * Lock out cancel/die interrupts until we exit the code section protected
1231  * by the LWLock. This ensures that interrupts will not interfere with
1232  * manipulations of data structures in shared memory.
1233  */
1234  HOLD_INTERRUPTS();
1235 
1236  /*
1237  * Loop here to try to acquire lock after each time we are signaled by
1238  * LWLockRelease.
1239  *
1240  * NOTE: it might seem better to have LWLockRelease actually grant us the
1241  * lock, rather than retrying and possibly having to go back to sleep. But
1242  * in practice that is no good because it means a process swap for every
1243  * lock acquisition when two or more processes are contending for the same
1244  * lock. Since LWLocks are normally used to protect not-very-long
1245  * sections of computation, a process needs to be able to acquire and
1246  * release the same lock many times during a single CPU time slice, even
1247  * in the presence of contention. The efficiency of being able to do that
1248  * outweighs the inefficiency of sometimes wasting a process dispatch
1249  * cycle because the lock is not free when a released waiter finally gets
1250  * to run. See pgsql-hackers archives for 29-Dec-01.
1251  */
1252  for (;;)
1253  {
1254  bool mustwait;
1255 
1256  /*
1257  * Try to grab the lock the first time, we're not in the waitqueue
1258  * yet/anymore.
1259  */
1260  mustwait = LWLockAttemptLock(lock, mode);
1261 
1262  if (!mustwait)
1263  {
1264  LOG_LWDEBUG("LWLockAcquire", lock, "immediately acquired lock");
1265  break; /* got the lock */
1266  }
1267 
1268  /*
1269  * Ok, at this point we couldn't grab the lock on the first try. We
1270  * cannot simply queue ourselves to the end of the list and wait to be
1271  * woken up because by now the lock could long have been released.
1272  * Instead add us to the queue and try to grab the lock again. If we
1273  * succeed we need to revert the queuing and be happy, otherwise we
1274  * recheck the lock. If we still couldn't grab it, we know that the
1275  * other locker will see our queue entries when releasing since they
1276  * existed before we checked for the lock.
1277  */
1278 
1279  /* add to the queue */
1280  LWLockQueueSelf(lock, mode);
1281 
1282  /* we're now guaranteed to be woken up if necessary */
1283  mustwait = LWLockAttemptLock(lock, mode);
1284 
1285  /* ok, grabbed the lock the second time round, need to undo queueing */
1286  if (!mustwait)
1287  {
1288  LOG_LWDEBUG("LWLockAcquire", lock, "acquired, undoing queue");
1289 
1290  LWLockDequeueSelf(lock);
1291  break;
1292  }
1293 
1294  /*
1295  * Wait until awakened.
1296  *
1297  * It is possible that we get awakened for a reason other than being
1298  * signaled by LWLockRelease. If so, loop back and wait again. Once
1299  * we've gotten the LWLock, re-increment the sema by the number of
1300  * additional signals received.
1301  */
1302  LOG_LWDEBUG("LWLockAcquire", lock, "waiting");
1303 
1304 #ifdef LWLOCK_STATS
1305  lwstats->block_count++;
1306 #endif
1307 
1308  LWLockReportWaitStart(lock);
1309  if (TRACE_POSTGRESQL_LWLOCK_WAIT_START_ENABLED())
1310  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1311 
1312  for (;;)
1313  {
1314  PGSemaphoreLock(proc->sem);
1315  if (proc->lwWaiting == LW_WS_NOT_WAITING)
1316  break;
1317  extraWaits++;
1318  }
1319 
1320  /* Retrying, allow LWLockRelease to release waiters again. */
1322 
1323 #ifdef LOCK_DEBUG
1324  {
1325  /* not waiting anymore */
1326  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1327 
1328  Assert(nwaiters < MAX_BACKENDS);
1329  }
1330 #endif
1331 
1332  if (TRACE_POSTGRESQL_LWLOCK_WAIT_DONE_ENABLED())
1333  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1335 
1336  LOG_LWDEBUG("LWLockAcquire", lock, "awakened");
1337 
1338  /* Now loop back and try to acquire lock again. */
1339  result = false;
1340  }
1341 
1342  if (TRACE_POSTGRESQL_LWLOCK_ACQUIRE_ENABLED())
1343  TRACE_POSTGRESQL_LWLOCK_ACQUIRE(T_NAME(lock), mode);
1344 
1345  /* Add lock to list of locks held by this backend */
1348 
1349  /*
1350  * Fix the process wait semaphore's count for any absorbed wakeups.
1351  */
1352  while (extraWaits-- > 0)
1353  PGSemaphoreUnlock(proc->sem);
1354 
1355  return result;
1356 }
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:367
static uint32 pg_atomic_fetch_sub_u32(volatile pg_atomic_uint32 *ptr, int32 sub_)
Definition: atomics.h:338
unsigned int uint32
Definition: c.h:490
#define PG_USED_FOR_ASSERTS_ONLY
Definition: c.h:166
static LWLockHandle held_lwlocks[MAX_SIMUL_LWLOCKS]
Definition: lwlock.c:230
static bool LWLockAttemptLock(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:811
static void LWLockReportWaitEnd(void)
Definition: lwlock.c:757
#define LW_FLAG_RELEASE_OK
Definition: lwlock.c:101
#define MAX_SIMUL_LWLOCKS
Definition: lwlock.c:220
#define T_NAME(lock)
Definition: lwlock.c:258
static int num_held_lwlocks
Definition: lwlock.c:229
#define LOG_LWDEBUG(a, b, c)
Definition: lwlock.c:323
static void LWLockQueueSelf(LWLock *lock, LWLockMode mode)
Definition: lwlock.c:1063
#define PRINT_LWDEBUG(a, b, c)
Definition: lwlock.c:322
static void LWLockReportWaitStart(LWLock *lock)
Definition: lwlock.c:748
static void LWLockDequeueSelf(LWLock *lock)
Definition: lwlock.c:1106
#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
#define MAX_BACKENDS
Definition: postmaster.h:78
PGPROC * MyProc
Definition: proc.c:66
LWLockMode mode
Definition: lwlock.c:226
LWLock * lock
Definition: lwlock.c:225
pg_atomic_uint32 state
Definition: lwlock.h:42
Definition: proc.h:162
PGSemaphore sem
Definition: proc.h:167
uint8 lwWaiting
Definition: proc.h:214

References Assert(), elog(), ERROR, held_lwlocks, HOLD_INTERRUPTS, IsUnderPostmaster, LWLockHandle::lock, LOG_LWDEBUG, LW_EXCLUSIVE, LW_FLAG_RELEASE_OK, LW_SHARED, LW_WS_NOT_WAITING, 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(), AtEOXact_LogicalRepWorkers(), AtPrepare_PredicateLocks(), attach_internal(), autoprewarm_main(), autoprewarm_start_worker(), AutoVacLauncherMain(), AutoVacuumRequestWork(), AutoVacWorkerMain(), BackendIdGetProc(), BackendIdGetTransactionIds(), BackendPidGetProc(), BackendXidGetPid(), BecomeLockGroupLeader(), BecomeLockGroupMember(), BootStrapCLOG(), BootStrapMultiXact(), BootStrapSUBTRANS(), 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(), FindAndDropRelationBuffers(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLeaderApplyWorkerPid(), 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(), KnownAssignedXidsCompress(), KnownAssignedXidsReset(), lock_twophase_recover(), LockAcquireExtended(), LockBuffer(), LockErrorCleanup(), LockGXact(), LockHasWaiters(), LockRefindAndRelease(), LockRelease(), LockReleaseAll(), LockWaiterCount(), logicalrep_launcher_attach_dshmem(), logicalrep_pa_worker_stop(), logicalrep_worker_attach(), logicalrep_worker_detach(), logicalrep_worker_launch(), logicalrep_worker_stop(), logicalrep_worker_stop_internal(), 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_build_snapshot(), pgstat_checkpointer_reset_all_cb(), pgstat_checkpointer_snapshot_cb(), pgstat_flush_io(), pgstat_flush_wal(), pgstat_io_reset_all_cb(), pgstat_io_snapshot_cb(), pgstat_lock_entry(), pgstat_lock_entry_shared(), 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(), ReplicationSlotName(), ReplicationSlotRelease(), ReplicationSlotsComputeLogicalRestartLSN(), ReplicationSlotsComputeRequiredLSN(), ReplicationSlotsComputeRequiredXmin(), ReplicationSlotsCountDBSlots(), ReplicationSlotsDropDBSlots(), replorigin_advance(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), replorigin_state_clear(), 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(), test_slru_page_exists(), test_slru_page_read(), test_slru_page_write(), 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 1423 of file lwlock.c.

1424 {
1425  PGPROC *proc = MyProc;
1426  bool mustwait;
1427  int extraWaits = 0;
1428 #ifdef LWLOCK_STATS
1429  lwlock_stats *lwstats;
1430 
1431  lwstats = get_lwlock_stats_entry(lock);
1432 #endif
1433 
1435 
1436  PRINT_LWDEBUG("LWLockAcquireOrWait", lock, mode);
1437 
1438  /* Ensure we will have room to remember the lock */
1440  elog(ERROR, "too many LWLocks taken");
1441 
1442  /*
1443  * Lock out cancel/die interrupts until we exit the code section protected
1444  * by the LWLock. This ensures that interrupts will not interfere with
1445  * manipulations of data structures in shared memory.
1446  */
1447  HOLD_INTERRUPTS();
1448 
1449  /*
1450  * NB: We're using nearly the same twice-in-a-row lock acquisition
1451  * protocol as LWLockAcquire(). Check its comments for details.
1452  */
1453  mustwait = LWLockAttemptLock(lock, mode);
1454 
1455  if (mustwait)
1456  {
1458 
1459  mustwait = LWLockAttemptLock(lock, mode);
1460 
1461  if (mustwait)
1462  {
1463  /*
1464  * Wait until awakened. Like in LWLockAcquire, be prepared for
1465  * bogus wakeups.
1466  */
1467  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "waiting");
1468 
1469 #ifdef LWLOCK_STATS
1470  lwstats->block_count++;
1471 #endif
1472 
1473  LWLockReportWaitStart(lock);
1474  if (TRACE_POSTGRESQL_LWLOCK_WAIT_START_ENABLED())
1475  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), mode);
1476 
1477  for (;;)
1478  {
1479  PGSemaphoreLock(proc->sem);
1480  if (proc->lwWaiting == LW_WS_NOT_WAITING)
1481  break;
1482  extraWaits++;
1483  }
1484 
1485 #ifdef LOCK_DEBUG
1486  {
1487  /* not waiting anymore */
1488  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1489 
1490  Assert(nwaiters < MAX_BACKENDS);
1491  }
1492 #endif
1493  if (TRACE_POSTGRESQL_LWLOCK_WAIT_DONE_ENABLED())
1494  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), mode);
1496 
1497  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "awakened");
1498  }
1499  else
1500  {
1501  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "acquired, undoing queue");
1502 
1503  /*
1504  * Got lock in the second attempt, undo queueing. We need to treat
1505  * this as having successfully acquired the lock, otherwise we'd
1506  * not necessarily wake up people we've prevented from acquiring
1507  * the lock.
1508  */
1509  LWLockDequeueSelf(lock);
1510  }
1511  }
1512 
1513  /*
1514  * Fix the process wait semaphore's count for any absorbed wakeups.
1515  */
1516  while (extraWaits-- > 0)
1517  PGSemaphoreUnlock(proc->sem);
1518 
1519  if (mustwait)
1520  {
1521  /* Failed to get lock, so release interrupt holdoff */
1523  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "failed");
1524  if (TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_FAIL_ENABLED())
1525  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_FAIL(T_NAME(lock), mode);
1526  }
1527  else
1528  {
1529  LOG_LWDEBUG("LWLockAcquireOrWait", lock, "succeeded");
1530  /* Add lock to list of locks held by this backend */
1533  if (TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT_ENABLED())
1534  TRACE_POSTGRESQL_LWLOCK_ACQUIRE_OR_WAIT(T_NAME(lock), mode);
1535  }
1536 
1537  return !mustwait;
1538 }
#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, LW_WS_NOT_WAITING, 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().

◆ LWLockAnyHeldByMe()

bool LWLockAnyHeldByMe ( LWLock lock,
int  nlocks,
size_t  stride 
)

Definition at line 1937 of file lwlock.c.

1938 {
1939  char *held_lock_addr;
1940  char *begin;
1941  char *end;
1942  int i;
1943 
1944  begin = (char *) lock;
1945  end = begin + nlocks * stride;
1946  for (i = 0; i < num_held_lwlocks; i++)
1947  {
1948  held_lock_addr = (char *) held_lwlocks[i].lock;
1949  if (held_lock_addr >= begin &&
1950  held_lock_addr < end &&
1951  (held_lock_addr - begin) % stride == 0)
1952  return true;
1953  }
1954  return false;
1955 }

References held_lwlocks, i, and num_held_lwlocks.

◆ LWLockConditionalAcquire()

bool LWLockConditionalAcquire ( LWLock lock,
LWLockMode  mode 
)

Definition at line 1366 of file lwlock.c.

1367 {
1368  bool mustwait;
1369 
1371 
1372  PRINT_LWDEBUG("LWLockConditionalAcquire", lock, mode);
1373 
1374  /* Ensure we will have room to remember the lock */
1376  elog(ERROR, "too many LWLocks taken");
1377 
1378  /*
1379  * Lock out cancel/die interrupts until we exit the code section protected
1380  * by the LWLock. This ensures that interrupts will not interfere with
1381  * manipulations of data structures in shared memory.
1382  */
1383  HOLD_INTERRUPTS();
1384 
1385  /* Check for the lock */
1386  mustwait = LWLockAttemptLock(lock, mode);
1387 
1388  if (mustwait)
1389  {
1390  /* Failed to get lock, so release interrupt holdoff */
1392 
1393  LOG_LWDEBUG("LWLockConditionalAcquire", lock, "failed");
1394  if (TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_FAIL_ENABLED())
1395  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_FAIL(T_NAME(lock), mode);
1396  }
1397  else
1398  {
1399  /* Add lock to list of locks held by this backend */
1402  if (TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE_ENABLED())
1403  TRACE_POSTGRESQL_LWLOCK_CONDACQUIRE(T_NAME(lock), mode);
1404  }
1405  return !mustwait;
1406 }

References Assert(), 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_io(), pgstat_flush_wal(), pgstat_lock_entry(), pgstat_lock_entry_shared(), pgstat_slru_flush(), ProcArrayEndTransaction(), SimpleLruWaitIO(), ss_report_location(), TransactionIdSetPageStatus(), and XLogNeedsFlush().

◆ LWLockHeldByMe()

◆ LWLockHeldByMeInMode()

◆ LWLockInitialize()

void LWLockInitialize ( LWLock lock,
int  tranche_id 
)

Definition at line 730 of file lwlock.c.

731 {
733 #ifdef LOCK_DEBUG
734  pg_atomic_init_u32(&lock->nwaiters, 0);
735 #endif
736  lock->tranche = tranche_id;
737  proclist_init(&lock->waiters);
738 }
static void pg_atomic_init_u32(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: atomics.h:218
static void proclist_init(proclist_head *list)
Definition: proclist.h:29
uint16 tranche
Definition: lwlock.h:41
proclist_head waiters
Definition: lwlock.h:43

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(), test_slru_shmem_startup(), and XLOGShmemInit().

◆ LWLockNewTrancheId()

int LWLockNewTrancheId ( void  )

Definition at line 627 of file lwlock.c.

628 {
629  int result;
630  int *LWLockCounter;
631 
632  LWLockCounter = (int *) ((char *) MainLWLockArray - sizeof(int));
634  result = (*LWLockCounter)++;
636 
637  return result;
638 }
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(), InitializeLWLocks(), and test_slru_shmem_startup().

◆ LWLockRegisterTranche()

void LWLockRegisterTranche ( int  tranche_id,
const char *  tranche_name 
)

Definition at line 651 of file lwlock.c.

652 {
653  /* This should only be called for user-defined tranches. */
654  if (tranche_id < LWTRANCHE_FIRST_USER_DEFINED)
655  return;
656 
657  /* Convert to array index. */
658  tranche_id -= LWTRANCHE_FIRST_USER_DEFINED;
659 
660  /* If necessary, create or enlarge array. */
661  if (tranche_id >= LWLockTrancheNamesAllocated)
662  {
663  int newalloc;
664 
665  newalloc = pg_nextpower2_32(Max(8, tranche_id + 1));
666 
667  if (LWLockTrancheNames == NULL)
668  LWLockTrancheNames = (const char **)
670  newalloc * sizeof(char *));
671  else
674  LWLockTrancheNamesAllocated = newalloc;
675  }
676 
677  LWLockTrancheNames[tranche_id] = tranche_name;
678 }
#define Max(x, y)
Definition: c.h:982
static int LWLockTrancheNamesAllocated
Definition: lwlock.c:205
static const char ** LWLockTrancheNames
Definition: lwlock.c:204
MemoryContext TopMemoryContext
Definition: mcxt.c:141
void * MemoryContextAllocZero(MemoryContext context, Size size)
Definition: mcxt.c:1048
#define repalloc0_array(pointer, type, oldcount, count)
Definition: palloc.h:110
static uint32 pg_nextpower2_32(uint32 num)
Definition: pg_bitutils.h:185

References LWLockTrancheNames, LWLockTrancheNamesAllocated, LWTRANCHE_FIRST_USER_DEFINED, Max, MemoryContextAllocZero(), pg_nextpower2_32(), repalloc0_array, and TopMemoryContext.

Referenced by apw_init_shmem(), CreateLWLocks(), and test_slru_shmem_startup().

◆ LWLockRelease()

void LWLockRelease ( LWLock lock)

Definition at line 1803 of file lwlock.c.

1804 {
1805  LWLockMode mode;
1806  uint32 oldstate;
1807  bool check_waiters;
1808  int i;
1809 
1810  /*
1811  * Remove lock from list of locks held. Usually, but not always, it will
1812  * be the latest-acquired lock; so search array backwards.
1813  */
1814  for (i = num_held_lwlocks; --i >= 0;)
1815  if (lock == held_lwlocks[i].lock)
1816  break;
1817 
1818  if (i < 0)
1819  elog(ERROR, "lock %s is not held", T_NAME(lock));
1820 
1821  mode = held_lwlocks[i].mode;
1822 
1823  num_held_lwlocks--;
1824  for (; i < num_held_lwlocks; i++)
1825  held_lwlocks[i] = held_lwlocks[i + 1];
1826 
1827  PRINT_LWDEBUG("LWLockRelease", lock, mode);
1828 
1829  /*
1830  * Release my hold on lock, after that it can immediately be acquired by
1831  * others, even if we still have to wakeup other waiters.
1832  */
1833  if (mode == LW_EXCLUSIVE)
1834  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_EXCLUSIVE);
1835  else
1836  oldstate = pg_atomic_sub_fetch_u32(&lock->state, LW_VAL_SHARED);
1837 
1838  /* nobody else can have that kind of lock */
1839  Assert(!(oldstate & LW_VAL_EXCLUSIVE));
1840 
1841  if (TRACE_POSTGRESQL_LWLOCK_RELEASE_ENABLED())
1842  TRACE_POSTGRESQL_LWLOCK_RELEASE(T_NAME(lock));
1843 
1844  /*
1845  * We're still waiting for backends to get scheduled, don't wake them up
1846  * again.
1847  */
1848  if ((oldstate & (LW_FLAG_HAS_WAITERS | LW_FLAG_RELEASE_OK)) ==
1850  (oldstate & LW_LOCK_MASK) == 0)
1851  check_waiters = true;
1852  else
1853  check_waiters = false;
1854 
1855  /*
1856  * As waking up waiters requires the spinlock to be acquired, only do so
1857  * if necessary.
1858  */
1859  if (check_waiters)
1860  {
1861  /* XXX: remove before commit? */
1862  LOG_LWDEBUG("LWLockRelease", lock, "releasing waiters");
1863  LWLockWakeup(lock);
1864  }
1865 
1866  /*
1867  * Now okay to allow cancel/die interrupts.
1868  */
1870 }
static uint32 pg_atomic_sub_fetch_u32(volatile pg_atomic_uint32 *ptr, int32 sub_)
Definition: atomics.h:396
#define LW_VAL_EXCLUSIVE
Definition: lwlock.c:104
static void LWLockWakeup(LWLock *lock)
Definition: lwlock.c:947
#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(), AtEOXact_LogicalRepWorkers(), AtPrepare_PredicateLocks(), attach_internal(), autoprewarm_main(), autoprewarm_start_worker(), AutoVacLauncherMain(), AutoVacuumRequestWork(), AutoVacWorkerMain(), BackendIdGetProc(), BackendIdGetTransactionIds(), BackendPidGetProc(), BackendXidGetPid(), BecomeLockGroupLeader(), BecomeLockGroupMember(), BootStrapCLOG(), BootStrapMultiXact(), BootStrapSUBTRANS(), 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(), FindAndDropRelationBuffers(), FinishPreparedTransaction(), FlushDatabaseBuffers(), FlushRelationBuffers(), FlushRelationsAllBuffers(), ForceTransactionIdLimitUpdate(), ForwardSyncRequest(), FreeWorkerInfo(), GetBackgroundWorkerPid(), GetBackgroundWorkerTypeByPid(), GetBlockerStatusData(), GetConflictingVirtualXIDs(), GetCurrentVirtualXIDs(), GetLastImportantRecPtr(), GetLastSegSwitchData(), GetLatestCommitTsData(), GetLeaderApplyWorkerPid(), 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(), KnownAssignedXidsCompress(), KnownAssignedXidsReset(), lock_twophase_recover(), LockAcquireExtended(), LockBuffer(), LockErrorCleanup(), LockGXact(), LockHasWaiters(), LockRefindAndRelease(), LockRelease(), LockReleaseAll(), LockWaiterCount(), logicalrep_launcher_attach_dshmem(), logicalrep_pa_worker_stop(), logicalrep_worker_attach(), logicalrep_worker_detach(), logicalrep_worker_launch(), logicalrep_worker_stop(), logicalrep_worker_stop_internal(), 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_build_snapshot(), pgstat_checkpointer_reset_all_cb(), pgstat_checkpointer_snapshot_cb(), pgstat_flush_io(), pgstat_flush_wal(), pgstat_io_reset_all_cb(), pgstat_io_snapshot_cb(), 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(), ReplicationSlotName(), ReplicationSlotRelease(), ReplicationSlotsComputeLogicalRestartLSN(), ReplicationSlotsComputeRequiredLSN(), ReplicationSlotsComputeRequiredXmin(), ReplicationSlotsCountDBSlots(), ReplicationSlotsDropDBSlots(), replorigin_advance(), replorigin_get_progress(), replorigin_session_advance(), replorigin_session_get_progress(), replorigin_session_reset(), replorigin_session_setup(), replorigin_state_clear(), 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(), test_slru_page_exists(), test_slru_page_read(), test_slru_page_readonly(), test_slru_page_write(), 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 1902 of file lwlock.c.

1903 {
1904  while (num_held_lwlocks > 0)
1905  {
1906  HOLD_INTERRUPTS(); /* match the upcoming RESUME_INTERRUPTS */
1907 
1909  }
1910 }
void LWLockRelease(LWLock *lock)
Definition: lwlock.c:1803

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 1876 of file lwlock.c.

1877 {
1878  LWLockWaitListLock(lock);
1879 
1880  /*
1881  * Set the variable's value before releasing the lock, that prevents race
1882  * a race condition wherein a new locker acquires the lock, but hasn't yet
1883  * set the variables value.
1884  */
1885  *valptr = val;
1886  LWLockWaitListUnlock(lock);
1887 
1888  LWLockRelease(lock);
1889 }
long val
Definition: informix.c:664
static void LWLockWaitListLock(LWLock *lock)
Definition: lwlock.c:882
static void LWLockWaitListUnlock(LWLock *lock)
Definition: lwlock.c:934

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

Referenced by WALInsertLockRelease().

◆ LWLockShmemSize()

Size LWLockShmemSize ( void  )

Definition at line 444 of file lwlock.c.

445 {
446  Size size;
447  int i;
448  int numLocks = NUM_FIXED_LWLOCKS;
449 
450  /* Calculate total number of locks needed in the main array. */
451  numLocks += NumLWLocksForNamedTranches();
452 
453  /* Space for the LWLock array. */
454  size = mul_size(numLocks, sizeof(LWLockPadded));
455 
456  /* Space for dynamic allocation counter, plus room for alignment. */
457  size = add_size(size, sizeof(int) + LWLOCK_PADDED_SIZE);
458 
459  /* space for named tranches. */
461 
462  /* space for name of each tranche. */
463  for (i = 0; i < NamedLWLockTrancheRequests; i++)
464  size = add_size(size, strlen(NamedLWLockTrancheRequestArray[i].tranche_name) + 1);
465 
466  return size;
467 }
static int NumLWLocksForNamedTranches(void)
Definition: lwlock.c:429
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  val 
)

Definition at line 1745 of file lwlock.c.

1746 {
1748  proclist_mutable_iter iter;
1749 
1750  PRINT_LWDEBUG("LWLockUpdateVar", lock, LW_EXCLUSIVE);
1751 
1753 
1754  LWLockWaitListLock(lock);
1755 
1757 
1758  /* Update the lock's value */
1759  *valptr = val;
1760 
1761  /*
1762  * See if there are any LW_WAIT_UNTIL_FREE waiters that need to be woken
1763  * up. They are always in the front of the queue.
1764  */
1765  proclist_foreach_modify(iter, &lock->waiters, lwWaitLink)
1766  {
1767  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1768 
1769  if (waiter->lwWaitMode != LW_WAIT_UNTIL_FREE)
1770  break;
1771 
1772  proclist_delete(&lock->waiters, iter.cur, lwWaitLink);
1773  proclist_push_tail(&wakeup, iter.cur, lwWaitLink);
1774 
1775  /* see LWLockWakeup() */
1776  Assert(waiter->lwWaiting == LW_WS_WAITING);
1777  waiter->lwWaiting = LW_WS_PENDING_WAKEUP;
1778  }
1779 
1780  /* We are done updating shared state of the lock itself. */
1781  LWLockWaitListUnlock(lock);
1782 
1783  /*
1784  * Awaken any waiters I removed from the queue.
1785  */
1786  proclist_foreach_modify(iter, &wakeup, lwWaitLink)
1787  {
1788  PGPROC *waiter = GetPGProcByNumber(iter.cur);
1789 
1790  proclist_delete(&wakeup, iter.cur, lwWaitLink);
1791  /* check comment in LWLockWakeup() about this barrier */
1792  pg_write_barrier();
1793  waiter->lwWaiting = LW_WS_NOT_WAITING;
1794  PGSemaphoreUnlock(waiter->sem);
1795  }
1796 }
#define pg_write_barrier()
Definition: atomics.h:154
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:236
#define GetPGProcByNumber(n)
Definition: proc.h:408
#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:215
static TimestampTz wakeup[NUM_WALRCV_WAKEUPS]
Definition: walreceiver.c:132

References Assert(), proclist_mutable_iter::cur, GetPGProcByNumber, LW_EXCLUSIVE, LW_VAL_EXCLUSIVE, LW_WAIT_UNTIL_FREE, LW_WS_NOT_WAITING, LW_WS_PENDING_WAKEUP, LW_WS_WAITING, 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, LWLock::waiters, and wakeup.

Referenced by WALInsertLockAcquireExclusive(), and WALInsertLockUpdateInsertingAt().

◆ LWLockWaitForVar()

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

Definition at line 1610 of file lwlock.c.

1611 {
1612  PGPROC *proc = MyProc;
1613  int extraWaits = 0;
1614  bool result = false;
1615 #ifdef LWLOCK_STATS
1616  lwlock_stats *lwstats;
1617 
1618  lwstats = get_lwlock_stats_entry(lock);
1619 #endif
1620 
1621  PRINT_LWDEBUG("LWLockWaitForVar", lock, LW_WAIT_UNTIL_FREE);
1622 
1623  /*
1624  * Lock out cancel/die interrupts while we sleep on the lock. There is no
1625  * cleanup mechanism to remove us from the wait queue if we got
1626  * interrupted.
1627  */
1628  HOLD_INTERRUPTS();
1629 
1630  /*
1631  * Loop here to check the lock's status after each time we are signaled.
1632  */
1633  for (;;)
1634  {
1635  bool mustwait;
1636 
1637  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1638  &result);
1639 
1640  if (!mustwait)
1641  break; /* the lock was free or value didn't match */
1642 
1643  /*
1644  * Add myself to wait queue. Note that this is racy, somebody else
1645  * could wakeup before we're finished queuing. NB: We're using nearly
1646  * the same twice-in-a-row lock acquisition protocol as
1647  * LWLockAcquire(). Check its comments for details. The only
1648  * difference is that we also have to check the variable's values when
1649  * checking the state of the lock.
1650  */
1652 
1653  /*
1654  * Set RELEASE_OK flag, to make sure we get woken up as soon as the
1655  * lock is released.
1656  */
1658 
1659  /*
1660  * We're now guaranteed to be woken up if necessary. Recheck the lock
1661  * and variables state.
1662  */
1663  mustwait = LWLockConflictsWithVar(lock, valptr, oldval, newval,
1664  &result);
1665 
1666  /* Ok, no conflict after we queued ourselves. Undo queueing. */
1667  if (!mustwait)
1668  {
1669  LOG_LWDEBUG("LWLockWaitForVar", lock, "free, undoing queue");
1670 
1671  LWLockDequeueSelf(lock);
1672  break;
1673  }
1674 
1675  /*
1676  * Wait until awakened.
1677  *
1678  * It is possible that we get awakened for a reason other than being
1679  * signaled by LWLockRelease. If so, loop back and wait again. Once
1680  * we've gotten the LWLock, re-increment the sema by the number of
1681  * additional signals received.
1682  */
1683  LOG_LWDEBUG("LWLockWaitForVar", lock, "waiting");
1684 
1685 #ifdef LWLOCK_STATS
1686  lwstats->block_count++;
1687 #endif
1688 
1689  LWLockReportWaitStart(lock);
1690  if (TRACE_POSTGRESQL_LWLOCK_WAIT_START_ENABLED())
1691  TRACE_POSTGRESQL_LWLOCK_WAIT_START(T_NAME(lock), LW_EXCLUSIVE);
1692 
1693  for (;;)
1694  {
1695  PGSemaphoreLock(proc->sem);
1696  if (proc->lwWaiting == LW_WS_NOT_WAITING)
1697  break;
1698  extraWaits++;
1699  }
1700 
1701 #ifdef LOCK_DEBUG
1702  {
1703  /* not waiting anymore */
1704  uint32 nwaiters PG_USED_FOR_ASSERTS_ONLY = pg_atomic_fetch_sub_u32(&lock->nwaiters, 1);
1705 
1706  Assert(nwaiters < MAX_BACKENDS);
1707  }
1708 #endif
1709 
1710  if (TRACE_POSTGRESQL_LWLOCK_WAIT_DONE_ENABLED())
1711  TRACE_POSTGRESQL_LWLOCK_WAIT_DONE(T_NAME(lock), LW_EXCLUSIVE);
1713 
1714  LOG_LWDEBUG("LWLockWaitForVar", lock, "awakened");
1715 
1716  /* Now loop back and check the status of the lock again. */
1717  }
1718 
1719  /*
1720  * Fix the process wait semaphore's count for any absorbed wakeups.
1721  */
1722  while (extraWaits-- > 0)
1723  PGSemaphoreUnlock(proc->sem);
1724 
1725  /*
1726  * Now okay to allow cancel/die interrupts.
1727  */
1729 
1730  return result;
1731 }
#define newval
static bool LWLockConflictsWithVar(LWLock *lock, uint64 *valptr, uint64 oldval, uint64 *newval, bool *result)
Definition: lwlock.c:1550

References Assert(), HOLD_INTERRUPTS, LOG_LWDEBUG, LW_EXCLUSIVE, LW_FLAG_RELEASE_OK, LW_WAIT_UNTIL_FREE, LW_WS_NOT_WAITING, 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 693 of file lwlock.c.

694 {
695  NamedLWLockTrancheRequest *request;
696 
698  elog(FATAL, "cannot request additional LWLocks outside shmem_request_hook");
699 
700  if (NamedLWLockTrancheRequestArray == NULL)
701  {
706  * sizeof(NamedLWLockTrancheRequest));
707  }
708 
710  {
712 
715  i * sizeof(NamedLWLockTrancheRequest));
717  }
718 
720  Assert(strlen(tranche_name) + 1 <= NAMEDATALEN);
721  strlcpy(request->tranche_name, tranche_name, NAMEDATALEN);
722  request->num_lwlocks = num_lwlocks;
724 }
#define FATAL
Definition: elog.h:41
static int NamedLWLockTrancheRequestsAllocated
Definition: lwlock.c:240
void * repalloc(void *pointer, Size size)
Definition: mcxt.c:1456
void * MemoryContextAlloc(MemoryContext context, Size size)
Definition: mcxt.c:1005
bool process_shmem_requests_in_progress
Definition: miscinit.c:1786
#define NAMEDATALEN
size_t strlcpy(char *dst, const char *src, size_t siz)
Definition: strlcpy.c:45
char tranche_name[NAMEDATALEN]
Definition: lwlock.c:235

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().

◆ StaticAssertDecl()

StaticAssertDecl ( sizeof(LWLock)<=  LWLOCK_PADDED_SIZE,
"Miscalculated LWLock padding"   
)

Variable Documentation

◆ MainLWLockArray

◆ NamedLWLockTrancheArray

PGDLLIMPORT NamedLWLockTranche* NamedLWLockTrancheArray
extern

Definition at line 251 of file lwlock.c.

Referenced by CreateLWLocks(), and InitializeLWLocks().

◆ NamedLWLockTrancheRequests