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procsignal.h File Reference
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Enumerations

enum  ProcSignalReason {
  PROCSIG_CATCHUP_INTERRUPT , PROCSIG_NOTIFY_INTERRUPT , PROCSIG_PARALLEL_MESSAGE , PROCSIG_WALSND_INIT_STOPPING ,
  PROCSIG_BARRIER , PROCSIG_LOG_MEMORY_CONTEXT , PROCSIG_RECOVERY_CONFLICT_DATABASE , PROCSIG_RECOVERY_CONFLICT_TABLESPACE ,
  PROCSIG_RECOVERY_CONFLICT_LOCK , PROCSIG_RECOVERY_CONFLICT_SNAPSHOT , PROCSIG_RECOVERY_CONFLICT_BUFFERPIN , PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK ,
  NUM_PROCSIGNALS
}
 
enum  ProcSignalBarrierType { PROCSIGNAL_BARRIER_PLACEHOLDER = 0 }
 

Functions

Size ProcSignalShmemSize (void)
 
void ProcSignalShmemInit (void)
 
void ProcSignalInit (int pss_idx)
 
int SendProcSignal (pid_t pid, ProcSignalReason reason, BackendId backendId)
 
uint64 EmitProcSignalBarrier (ProcSignalBarrierType type)
 
void WaitForProcSignalBarrier (uint64 generation)
 
void ProcessProcSignalBarrier (void)
 
void procsignal_sigusr1_handler (SIGNAL_ARGS)
 

Enumeration Type Documentation

◆ ProcSignalBarrierType

Enumerator
PROCSIGNAL_BARRIER_PLACEHOLDER 

Definition at line 50 of file procsignal.h.

51 {
52  /*
53  * XXX. PROCSIGNAL_BARRIER_PLACEHOLDER should be replaced when the first
54  * real user of the ProcSignalBarrier mechanism is added. It's just here
55  * for now because we can't have an empty enum.
56  */
ProcSignalBarrierType
Definition: procsignal.h:51
@ PROCSIGNAL_BARRIER_PLACEHOLDER
Definition: procsignal.h:57

◆ ProcSignalReason

Enumerator
PROCSIG_CATCHUP_INTERRUPT 
PROCSIG_NOTIFY_INTERRUPT 
PROCSIG_PARALLEL_MESSAGE 
PROCSIG_WALSND_INIT_STOPPING 
PROCSIG_BARRIER 
PROCSIG_LOG_MEMORY_CONTEXT 
PROCSIG_RECOVERY_CONFLICT_DATABASE 
PROCSIG_RECOVERY_CONFLICT_TABLESPACE 
PROCSIG_RECOVERY_CONFLICT_LOCK 
PROCSIG_RECOVERY_CONFLICT_SNAPSHOT 
PROCSIG_RECOVERY_CONFLICT_BUFFERPIN 
PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK 
NUM_PROCSIGNALS 

Definition at line 30 of file procsignal.h.

31 {
32  PROCSIG_CATCHUP_INTERRUPT, /* sinval catchup interrupt */
33  PROCSIG_NOTIFY_INTERRUPT, /* listen/notify interrupt */
34  PROCSIG_PARALLEL_MESSAGE, /* message from cooperating parallel backend */
35  PROCSIG_WALSND_INIT_STOPPING, /* ask walsenders to prepare for shutdown */
36  PROCSIG_BARRIER, /* global barrier interrupt */
37  PROCSIG_LOG_MEMORY_CONTEXT, /* ask backend to log the memory contexts */
38 
39  /* Recovery conflict reasons */
46 
47  NUM_PROCSIGNALS /* Must be last! */
ProcSignalReason
Definition: procsignal.h:31
@ PROCSIG_PARALLEL_MESSAGE
Definition: procsignal.h:34
@ PROCSIG_RECOVERY_CONFLICT_BUFFERPIN
Definition: procsignal.h:44
@ PROCSIG_CATCHUP_INTERRUPT
Definition: procsignal.h:32
@ PROCSIG_RECOVERY_CONFLICT_LOCK
Definition: procsignal.h:42
@ PROCSIG_LOG_MEMORY_CONTEXT
Definition: procsignal.h:37
@ PROCSIG_BARRIER
Definition: procsignal.h:36
@ PROCSIG_RECOVERY_CONFLICT_DATABASE
Definition: procsignal.h:40
@ PROCSIG_WALSND_INIT_STOPPING
Definition: procsignal.h:35
@ PROCSIG_RECOVERY_CONFLICT_SNAPSHOT
Definition: procsignal.h:43
@ PROCSIG_NOTIFY_INTERRUPT
Definition: procsignal.h:33
@ PROCSIG_RECOVERY_CONFLICT_TABLESPACE
Definition: procsignal.h:41
@ NUM_PROCSIGNALS
Definition: procsignal.h:47
@ PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK
Definition: procsignal.h:45

Function Documentation

◆ EmitProcSignalBarrier()

uint64 EmitProcSignalBarrier ( ProcSignalBarrierType  type)

Definition at line 332 of file procsignal.c.

333 {
334  uint32 flagbit = 1 << (uint32) type;
335  uint64 generation;
336 
337  /*
338  * Set all the flags.
339  *
340  * Note that pg_atomic_fetch_or_u32 has full barrier semantics, so this is
341  * totally ordered with respect to anything the caller did before, and
342  * anything that we do afterwards. (This is also true of the later call to
343  * pg_atomic_add_fetch_u64.)
344  */
345  for (int i = 0; i < NumProcSignalSlots; i++)
346  {
347  volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
348 
350  }
351 
352  /*
353  * Increment the generation counter.
354  */
355  generation =
357 
358  /*
359  * Signal all the processes, so that they update their advertised barrier
360  * generation.
361  *
362  * Concurrency is not a problem here. Backends that have exited don't
363  * matter, and new backends that have joined since we entered this
364  * function must already have current state, since the caller is
365  * responsible for making sure that the relevant state is entirely visible
366  * before calling this function in the first place. We still have to wake
367  * them up - because we can't distinguish between such backends and older
368  * backends that need to update state - but they won't actually need to
369  * change any state.
370  */
371  for (int i = NumProcSignalSlots - 1; i >= 0; i--)
372  {
373  volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
374  pid_t pid = slot->pss_pid;
375 
376  if (pid != 0)
377  {
378  /* see SendProcSignal for details */
379  slot->pss_signalFlags[PROCSIG_BARRIER] = true;
380  kill(pid, SIGUSR1);
381  }
382  }
383 
384  return generation;
385 }
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372
static uint64 pg_atomic_add_fetch_u64(volatile pg_atomic_uint64 *ptr, int64 add_)
Definition: atomics.h:504
unsigned int uint32
Definition: c.h:441
int i
Definition: isn.c:73
static ProcSignalHeader * ProcSignal
Definition: procsignal.c:98
#define NumProcSignalSlots
Definition: procsignal.c:88
ProcSignalSlot psh_slot[FLEXIBLE_ARRAY_MEMBER]
Definition: procsignal.c:80
pg_atomic_uint64 psh_barrierGeneration
Definition: procsignal.c:79
volatile pid_t pss_pid
Definition: procsignal.c:64
volatile sig_atomic_t pss_signalFlags[NUM_PROCSIGNALS]
Definition: procsignal.c:65
pg_atomic_uint32 pss_barrierCheckMask
Definition: procsignal.c:67
#define kill(pid, sig)
Definition: win32_port.h:464
#define SIGUSR1
Definition: win32_port.h:179

References i, kill, NumProcSignalSlots, pg_atomic_add_fetch_u64(), pg_atomic_fetch_or_u32(), PROCSIG_BARRIER, ProcSignal, ProcSignalHeader::psh_barrierGeneration, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_barrierCheckMask, ProcSignalSlot::pss_pid, ProcSignalSlot::pss_signalFlags, SIGUSR1, and generate_unaccent_rules::type.

◆ ProcessProcSignalBarrier()

void ProcessProcSignalBarrier ( void  )

Definition at line 453 of file procsignal.c.

454 {
455  uint64 local_gen;
456  uint64 shared_gen;
457  volatile uint32 flags;
458 
460 
461  /* Exit quickly if there's no work to do. */
463  return;
464  ProcSignalBarrierPending = false;
465 
466  /*
467  * It's not unlikely to process multiple barriers at once, before the
468  * signals for all the barriers have arrived. To avoid unnecessary work in
469  * response to subsequent signals, exit early if we already have processed
470  * all of them.
471  */
474 
475  Assert(local_gen <= shared_gen);
476 
477  if (local_gen == shared_gen)
478  return;
479 
480  /*
481  * Get and clear the flags that are set for this backend. Note that
482  * pg_atomic_exchange_u32 is a full barrier, so we're guaranteed that the
483  * read of the barrier generation above happens before we atomically
484  * extract the flags, and that any subsequent state changes happen
485  * afterward.
486  *
487  * NB: In order to avoid race conditions, we must zero
488  * pss_barrierCheckMask first and only afterwards try to do barrier
489  * processing. If we did it in the other order, someone could send us
490  * another barrier of some type right after we called the
491  * barrier-processing function but before we cleared the bit. We would
492  * have no way of knowing that the bit needs to stay set in that case, so
493  * the need to call the barrier-processing function again would just get
494  * forgotten. So instead, we tentatively clear all the bits and then put
495  * back any for which we don't manage to successfully absorb the barrier.
496  */
498 
499  /*
500  * If there are no flags set, then we can skip doing any real work.
501  * Otherwise, establish a PG_TRY block, so that we don't lose track of
502  * which types of barrier processing are needed if an ERROR occurs.
503  */
504  if (flags != 0)
505  {
506  bool success = true;
507 
508  PG_TRY();
509  {
510  /*
511  * Process each type of barrier. The barrier-processing functions
512  * should normally return true, but may return false if the
513  * barrier can't be absorbed at the current time. This should be
514  * rare, because it's pretty expensive. Every single
515  * CHECK_FOR_INTERRUPTS() will return here until we manage to
516  * absorb the barrier, and that cost will add up in a hurry.
517  *
518  * NB: It ought to be OK to call the barrier-processing functions
519  * unconditionally, but it's more efficient to call only the ones
520  * that might need us to do something based on the flags.
521  */
522  while (flags != 0)
523  {
525  bool processed = true;
526 
528  switch (type)
529  {
531  processed = ProcessBarrierPlaceholder();
532  break;
533  }
534 
535  /*
536  * To avoid an infinite loop, we must always unset the bit in
537  * flags.
538  */
539  BARRIER_CLEAR_BIT(flags, type);
540 
541  /*
542  * If we failed to process the barrier, reset the shared bit
543  * so we try again later, and set a flag so that we don't bump
544  * our generation.
545  */
546  if (!processed)
547  {
549  success = false;
550  }
551  }
552  }
553  PG_CATCH();
554  {
555  /*
556  * If an ERROR occurred, we'll need to try again later to handle
557  * that barrier type and any others that haven't been handled yet
558  * or weren't successfully absorbed.
559  */
561  PG_RE_THROW();
562  }
563  PG_END_TRY();
564 
565  /*
566  * If some barrier types were not successfully absorbed, we will have
567  * to try again later.
568  */
569  if (!success)
570  return;
571  }
572 
573  /*
574  * State changes related to all types of barriers that might have been
575  * emitted have now been handled, so we can update our notion of the
576  * generation to the one we observed before beginning the updates. If
577  * things have changed further, it'll get fixed up when this function is
578  * next called.
579  */
582 }
static void pg_atomic_write_u64(volatile pg_atomic_uint64 *ptr, uint64 val)
Definition: atomics.h:438
static uint32 pg_atomic_exchange_u32(volatile pg_atomic_uint32 *ptr, uint32 newval)
Definition: atomics.h:292
static uint64 pg_atomic_read_u64(volatile pg_atomic_uint64 *ptr)
Definition: atomics.h:429
void ConditionVariableBroadcast(ConditionVariable *cv)
#define PG_RE_THROW()
Definition: elog.h:340
#define PG_END_TRY()
Definition: elog.h:324
#define PG_TRY()
Definition: elog.h:299
#define PG_CATCH()
Definition: elog.h:309
volatile sig_atomic_t ProcSignalBarrierPending
Definition: globals.c:37
static bool success
Definition: initdb.c:166
Assert(fmt[strlen(fmt) - 1] !='\n')
static int pg_rightmost_one_pos32(uint32 word)
Definition: pg_bitutils.h:79
static void ResetProcSignalBarrierBits(uint32 flags)
Definition: procsignal.c:590
static bool ProcessBarrierPlaceholder(void)
Definition: procsignal.c:598
static ProcSignalSlot * MyProcSignalSlot
Definition: procsignal.c:99
#define BARRIER_CLEAR_BIT(flags, type)
Definition: procsignal.c:95
ConditionVariable pss_barrierCV
Definition: procsignal.c:68
pg_atomic_uint64 pss_barrierGeneration
Definition: procsignal.c:66

References Assert(), BARRIER_CLEAR_BIT, ConditionVariableBroadcast(), MyProcSignalSlot, pg_atomic_exchange_u32(), pg_atomic_read_u64(), pg_atomic_write_u64(), PG_CATCH, PG_END_TRY, PG_RE_THROW, pg_rightmost_one_pos32(), PG_TRY, ProcessBarrierPlaceholder(), ProcSignal, PROCSIGNAL_BARRIER_PLACEHOLDER, ProcSignalBarrierPending, ProcSignalHeader::psh_barrierGeneration, ProcSignalSlot::pss_barrierCheckMask, ProcSignalSlot::pss_barrierCV, ProcSignalSlot::pss_barrierGeneration, ResetProcSignalBarrierBits(), success, and generate_unaccent_rules::type.

Referenced by BufferSync(), CheckpointWriteDelay(), HandleAutoVacLauncherInterrupts(), HandleCheckpointerInterrupts(), HandleMainLoopInterrupts(), HandlePgArchInterrupts(), HandleStartupProcInterrupts(), HandleWalWriterInterrupts(), and ProcessInterrupts().

◆ procsignal_sigusr1_handler()

void procsignal_sigusr1_handler ( SIGNAL_ARGS  )

Definition at line 642 of file procsignal.c.

643 {
644  int save_errno = errno;
645 
648 
651 
654 
657 
660 
663 
666 
669 
672 
675 
678 
681 
682  SetLatch(MyLatch);
683 
684  errno = save_errno;
685 }
void HandleNotifyInterrupt(void)
Definition: async.c:1853
void HandleParallelMessageInterrupt(void)
Definition: parallel.c:1003
struct Latch * MyLatch
Definition: globals.c:57
void SetLatch(Latch *latch)
Definition: latch.c:567
void HandleLogMemoryContextInterrupt(void)
Definition: mcxt.c:1024
void RecoveryConflictInterrupt(ProcSignalReason reason)
Definition: postgres.c:2989
static bool CheckProcSignal(ProcSignalReason reason)
Definition: procsignal.c:621
static void HandleProcSignalBarrierInterrupt(void)
Definition: procsignal.c:437
void HandleCatchupInterrupt(void)
Definition: sinval.c:156
void HandleWalSndInitStopping(void)
Definition: walsender.c:3132

References CheckProcSignal(), HandleCatchupInterrupt(), HandleLogMemoryContextInterrupt(), HandleNotifyInterrupt(), HandleParallelMessageInterrupt(), HandleProcSignalBarrierInterrupt(), HandleWalSndInitStopping(), MyLatch, PROCSIG_BARRIER, PROCSIG_CATCHUP_INTERRUPT, PROCSIG_LOG_MEMORY_CONTEXT, PROCSIG_NOTIFY_INTERRUPT, PROCSIG_PARALLEL_MESSAGE, PROCSIG_RECOVERY_CONFLICT_BUFFERPIN, PROCSIG_RECOVERY_CONFLICT_DATABASE, PROCSIG_RECOVERY_CONFLICT_LOCK, PROCSIG_RECOVERY_CONFLICT_SNAPSHOT, PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK, PROCSIG_RECOVERY_CONFLICT_TABLESPACE, PROCSIG_WALSND_INIT_STOPPING, RecoveryConflictInterrupt(), and SetLatch().

Referenced by autoprewarm_main(), AutoVacLauncherMain(), AutoVacWorkerMain(), BackgroundWriterMain(), CheckpointerMain(), PgArchiverMain(), PostgresMain(), StartBackgroundWorker(), StartupProcessMain(), WalReceiverMain(), WalSndSignals(), and WalWriterMain().

◆ ProcSignalInit()

void ProcSignalInit ( int  pss_idx)

Definition at line 161 of file procsignal.c.

162 {
163  ProcSignalSlot *slot;
164  uint64 barrier_generation;
165 
166  Assert(pss_idx >= 1 && pss_idx <= NumProcSignalSlots);
167 
168  slot = &ProcSignal->psh_slot[pss_idx - 1];
169 
170  /* sanity check */
171  if (slot->pss_pid != 0)
172  elog(LOG, "process %d taking over ProcSignal slot %d, but it's not empty",
173  MyProcPid, pss_idx);
174 
175  /* Clear out any leftover signal reasons */
176  MemSet(slot->pss_signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
177 
178  /*
179  * Initialize barrier state. Since we're a brand-new process, there
180  * shouldn't be any leftover backend-private state that needs to be
181  * updated. Therefore, we can broadcast the latest barrier generation and
182  * disregard any previously-set check bits.
183  *
184  * NB: This only works if this initialization happens early enough in the
185  * startup sequence that we haven't yet cached any state that might need
186  * to be invalidated. That's also why we have a memory barrier here, to be
187  * sure that any later reads of memory happen strictly after this.
188  */
190  barrier_generation =
192  pg_atomic_write_u64(&slot->pss_barrierGeneration, barrier_generation);
194 
195  /* Mark slot with my PID */
196  slot->pss_pid = MyProcPid;
197 
198  /* Remember slot location for CheckProcSignal */
199  MyProcSignalSlot = slot;
200 
201  /* Set up to release the slot on process exit */
203 }
#define pg_memory_barrier()
Definition: atomics.h:145
static void pg_atomic_write_u32(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: atomics.h:258
#define MemSet(start, val, len)
Definition: c.h:1008
#define LOG
Definition: elog.h:25
#define elog(elevel,...)
Definition: elog.h:218
int MyProcPid
Definition: globals.c:43
void on_shmem_exit(pg_on_exit_callback function, Datum arg)
Definition: ipc.c:361
#define Int32GetDatum(X)
Definition: postgres.h:523
static void CleanupProcSignalState(int status, Datum arg)
Definition: procsignal.c:212

References Assert(), CleanupProcSignalState(), elog, Int32GetDatum, LOG, MemSet, MyProcPid, MyProcSignalSlot, NUM_PROCSIGNALS, NumProcSignalSlots, on_shmem_exit(), pg_atomic_read_u64(), pg_atomic_write_u32(), pg_atomic_write_u64(), pg_memory_barrier, ProcSignal, ProcSignalHeader::psh_barrierGeneration, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_barrierCheckMask, ProcSignalSlot::pss_barrierGeneration, ProcSignalSlot::pss_pid, and ProcSignalSlot::pss_signalFlags.

Referenced by AuxiliaryProcessMain(), and InitPostgres().

◆ ProcSignalShmemInit()

void ProcSignalShmemInit ( void  )

Definition at line 125 of file procsignal.c.

126 {
127  Size size = ProcSignalShmemSize();
128  bool found;
129 
131  ShmemInitStruct("ProcSignal", size, &found);
132 
133  /* If we're first, initialize. */
134  if (!found)
135  {
136  int i;
137 
139 
140  for (i = 0; i < NumProcSignalSlots; ++i)
141  {
142  ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
143 
144  slot->pss_pid = 0;
145  MemSet(slot->pss_signalFlags, 0, sizeof(slot->pss_signalFlags));
149  }
150  }
151 }
static void pg_atomic_init_u32(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: atomics.h:223
static void pg_atomic_init_u64(volatile pg_atomic_uint64 *ptr, uint64 val)
Definition: atomics.h:415
#define PG_UINT64_MAX
Definition: c.h:528
size_t Size
Definition: c.h:540
void ConditionVariableInit(ConditionVariable *cv)
Size ProcSignalShmemSize(void)
Definition: procsignal.c:111
void * ShmemInitStruct(const char *name, Size size, bool *foundPtr)
Definition: shmem.c:396

References ConditionVariableInit(), i, MemSet, NumProcSignalSlots, pg_atomic_init_u32(), pg_atomic_init_u64(), PG_UINT64_MAX, ProcSignal, ProcSignalShmemSize(), ProcSignalHeader::psh_barrierGeneration, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_barrierCheckMask, ProcSignalSlot::pss_barrierCV, ProcSignalSlot::pss_barrierGeneration, ProcSignalSlot::pss_pid, ProcSignalSlot::pss_signalFlags, and ShmemInitStruct().

Referenced by CreateSharedMemoryAndSemaphores().

◆ ProcSignalShmemSize()

Size ProcSignalShmemSize ( void  )

Definition at line 111 of file procsignal.c.

112 {
113  Size size;
114 
115  size = mul_size(NumProcSignalSlots, sizeof(ProcSignalSlot));
116  size = add_size(size, offsetof(ProcSignalHeader, psh_slot));
117  return size;
118 }
#define offsetof(type, field)
Definition: c.h:727
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(), mul_size(), NumProcSignalSlots, and offsetof.

Referenced by CalculateShmemSize(), and ProcSignalShmemInit().

◆ SendProcSignal()

int SendProcSignal ( pid_t  pid,
ProcSignalReason  reason,
BackendId  backendId 
)

Definition at line 261 of file procsignal.c.

262 {
263  volatile ProcSignalSlot *slot;
264 
265  if (backendId != InvalidBackendId)
266  {
267  slot = &ProcSignal->psh_slot[backendId - 1];
268 
269  /*
270  * Note: Since there's no locking, it's possible that the target
271  * process detaches from shared memory and exits right after this
272  * test, before we set the flag and send signal. And the signal slot
273  * might even be recycled by a new process, so it's remotely possible
274  * that we set a flag for a wrong process. That's OK, all the signals
275  * are such that no harm is done if they're mistakenly fired.
276  */
277  if (slot->pss_pid == pid)
278  {
279  /* Atomically set the proper flag */
280  slot->pss_signalFlags[reason] = true;
281  /* Send signal */
282  return kill(pid, SIGUSR1);
283  }
284  }
285  else
286  {
287  /*
288  * BackendId not provided, so search the array using pid. We search
289  * the array back to front so as to reduce search overhead. Passing
290  * InvalidBackendId means that the target is most likely an auxiliary
291  * process, which will have a slot near the end of the array.
292  */
293  int i;
294 
295  for (i = NumProcSignalSlots - 1; i >= 0; i--)
296  {
297  slot = &ProcSignal->psh_slot[i];
298 
299  if (slot->pss_pid == pid)
300  {
301  /* the above note about race conditions applies here too */
302 
303  /* Atomically set the proper flag */
304  slot->pss_signalFlags[reason] = true;
305  /* Send signal */
306  return kill(pid, SIGUSR1);
307  }
308  }
309  }
310 
311  errno = ESRCH;
312  return -1;
313 }
#define InvalidBackendId
Definition: backendid.h:23

References i, InvalidBackendId, kill, NumProcSignalSlots, ProcSignal, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_pid, ProcSignalSlot::pss_signalFlags, and SIGUSR1.

Referenced by CancelDBBackends(), mq_putmessage(), ParallelWorkerShutdown(), pg_log_backend_memory_contexts(), SICleanupQueue(), SignalBackends(), SignalVirtualTransaction(), and WalSndInitStopping().

◆ WaitForProcSignalBarrier()

void WaitForProcSignalBarrier ( uint64  generation)

Definition at line 392 of file procsignal.c.

393 {
395 
396  for (int i = NumProcSignalSlots - 1; i >= 0; i--)
397  {
398  ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
399  uint64 oldval;
400 
401  /*
402  * It's important that we check only pss_barrierGeneration here and
403  * not pss_barrierCheckMask. Bits in pss_barrierCheckMask get cleared
404  * before the barrier is actually absorbed, but pss_barrierGeneration
405  * is updated only afterward.
406  */
407  oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
408  while (oldval < generation)
409  {
412  oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
413  }
415  }
416 
417  /*
418  * The caller is probably calling this function because it wants to read
419  * the shared state or perform further writes to shared state once all
420  * backends are known to have absorbed the barrier. However, the read of
421  * pss_barrierGeneration was performed unlocked; insert a memory barrier
422  * to separate it from whatever follows.
423  */
425 }
void ConditionVariableSleep(ConditionVariable *cv, uint32 wait_event_info)
void ConditionVariableCancelSleep(void)
@ WAIT_EVENT_PROC_SIGNAL_BARRIER
Definition: wait_event.h:119

References Assert(), ConditionVariableCancelSleep(), ConditionVariableSleep(), i, NumProcSignalSlots, pg_atomic_read_u64(), pg_memory_barrier, ProcSignal, ProcSignalHeader::psh_barrierGeneration, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_barrierCV, ProcSignalSlot::pss_barrierGeneration, and WAIT_EVENT_PROC_SIGNAL_BARRIER.