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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_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 49 of file procsignal.h.

50 {
51  /*
52  * XXX. PROCSIGNAL_BARRIER_PLACEHOLDER should be replaced when the first
53  * real user of the ProcSignalBarrier mechanism is added. It's just here
54  * for now because we can't have an empty enum.
55  */
ProcSignalBarrierType
Definition: procsignal.h:49

◆ ProcSignalReason

Enumerator
PROCSIG_CATCHUP_INTERRUPT 
PROCSIG_NOTIFY_INTERRUPT 
PROCSIG_PARALLEL_MESSAGE 
PROCSIG_WALSND_INIT_STOPPING 
PROCSIG_BARRIER 
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.

Function Documentation

◆ EmitProcSignalBarrier()

uint64 EmitProcSignalBarrier ( ProcSignalBarrierType  type)

Definition at line 321 of file procsignal.c.

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

322 {
323  uint32 flagbit = 1 << (uint32) type;
324  uint64 generation;
325 
326  /*
327  * Set all the flags.
328  *
329  * Note that pg_atomic_fetch_or_u32 has full barrier semantics, so this is
330  * totally ordered with respect to anything the caller did before, and
331  * anything that we do afterwards. (This is also true of the later call to
332  * pg_atomic_add_fetch_u64.)
333  */
334  for (int i = 0; i < NumProcSignalSlots; i++)
335  {
336  volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
337 
339  }
340 
341  /*
342  * Increment the generation counter.
343  */
344  generation =
346 
347  /*
348  * Signal all the processes, so that they update their advertised barrier
349  * generation.
350  *
351  * Concurrency is not a problem here. Backends that have exited don't
352  * matter, and new backends that have joined since we entered this
353  * function must already have current state, since the caller is
354  * responsible for making sure that the relevant state is entirely visible
355  * before calling this function in the first place. We still have to wake
356  * them up - because we can't distinguish between such backends and older
357  * backends that need to update state - but they won't actually need to
358  * change any state.
359  */
360  for (int i = NumProcSignalSlots - 1; i >= 0; i--)
361  {
362  volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
363  pid_t pid = slot->pss_pid;
364 
365  if (pid != 0)
366  {
367  /* see SendProcSignal for details */
368  slot->pss_signalFlags[PROCSIG_BARRIER] = true;
369  kill(pid, SIGUSR1);
370  }
371  }
372 
373  return generation;
374 }
#define SIGUSR1
Definition: win32_port.h:171
pg_atomic_uint64 psh_barrierGeneration
Definition: procsignal.c:75
#define kill(pid, sig)
Definition: win32_port.h:454
ProcSignalSlot psh_slot[FLEXIBLE_ARRAY_MEMBER]
Definition: procsignal.c:76
pg_atomic_uint32 pss_barrierCheckMask
Definition: procsignal.c:64
unsigned int uint32
Definition: c.h:429
static ProcSignalHeader * ProcSignal
Definition: procsignal.c:90
static uint64 pg_atomic_add_fetch_u64(volatile pg_atomic_uint64 *ptr, int64 add_)
Definition: atomics.h:504
int i
sig_atomic_t pss_signalFlags[NUM_PROCSIGNALS]
Definition: procsignal.c:62
#define NumProcSignalSlots
Definition: procsignal.c:84
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:372

◆ ProcessProcSignalBarrier()

void ProcessProcSignalBarrier ( void  )

Definition at line 452 of file procsignal.c.

References Assert, BARRIER_SHOULD_CHECK, pg_atomic_exchange_u32(), pg_atomic_read_u64(), pg_atomic_write_u64(), ProcessBarrierPlaceholder(), PROCSIGNAL_BARRIER_PLACEHOLDER, ProcSignalBarrierPending, ProcSignalHeader::psh_barrierGeneration, ProcSignalSlot::pss_barrierCheckMask, and ProcSignalSlot::pss_barrierGeneration.

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

453 {
454  uint64 local_gen;
455  uint64 shared_gen;
456  uint32 flags;
457 
459 
460  /* Exit quickly if there's no work to do. */
462  return;
463  ProcSignalBarrierPending = false;
464 
465  /*
466  * It's not unlikely to process multiple barriers at once, before the
467  * signals for all the barriers have arrived. To avoid unnecessary work in
468  * response to subsequent signals, exit early if we already have processed
469  * all of them.
470  */
473 
474  Assert(local_gen <= shared_gen);
475 
476  if (local_gen == shared_gen)
477  return;
478 
479  /*
480  * Get and clear the flags that are set for this backend. Note that
481  * pg_atomic_exchange_u32 is a full barrier, so we're guaranteed that the
482  * read of the barrier generation above happens before we atomically
483  * extract the flags, and that any subsequent state changes happen
484  * afterward.
485  */
487 
488  /*
489  * Process each type of barrier. It's important that nothing we call from
490  * here throws an error, because pss_barrierCheckMask has already been
491  * cleared. If we jumped out of here before processing all barrier types,
492  * then we'd forget about the need to do so later.
493  *
494  * NB: It ought to be OK to call the barrier-processing functions
495  * unconditionally, but it's more efficient to call only the ones that
496  * might need us to do something based on the flags.
497  */
500 
501  /*
502  * State changes related to all types of barriers that might have been
503  * emitted have now been handled, so we can update our notion of the
504  * generation to the one we observed before beginning the updates. If
505  * things have changed further, it'll get fixed up when this function is
506  * next called.
507  */
509 }
pg_atomic_uint64 psh_barrierGeneration
Definition: procsignal.c:75
static void ProcessBarrierPlaceholder(void)
Definition: procsignal.c:512
pg_atomic_uint64 pss_barrierGeneration
Definition: procsignal.c:63
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
pg_atomic_uint32 pss_barrierCheckMask
Definition: procsignal.c:64
unsigned int uint32
Definition: c.h:429
static ProcSignalHeader * ProcSignal
Definition: procsignal.c:90
#define Assert(condition)
Definition: c.h:800
volatile sig_atomic_t ProcSignalBarrierPending
Definition: globals.c:35
#define BARRIER_SHOULD_CHECK(flags, type)
Definition: procsignal.c:87
static uint64 pg_atomic_read_u64(volatile pg_atomic_uint64 *ptr)
Definition: atomics.h:429
static volatile ProcSignalSlot * MyProcSignalSlot
Definition: procsignal.c:91

◆ procsignal_sigusr1_handler()

void procsignal_sigusr1_handler ( SIGNAL_ARGS  )

Definition at line 551 of file procsignal.c.

References CheckProcSignal(), HandleCatchupInterrupt(), HandleNotifyInterrupt(), HandleParallelMessageInterrupt(), HandleProcSignalBarrierInterrupt(), HandleWalSndInitStopping(), latch_sigusr1_handler(), MyLatch, PROCSIG_BARRIER, PROCSIG_CATCHUP_INTERRUPT, 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(), PostgresMain(), StartBackgroundWorker(), StartupProcessMain(), WalReceiverMain(), WalSndSignals(), and WalWriterMain().

552 {
553  int save_errno = errno;
554 
557 
560 
563 
566 
569 
572 
575 
578 
581 
584 
587 
588  SetLatch(MyLatch);
589 
591 
592  errno = save_errno;
593 }
void RecoveryConflictInterrupt(ProcSignalReason reason)
Definition: postgres.c:2896
static void HandleProcSignalBarrierInterrupt(void)
Definition: procsignal.c:436
void SetLatch(Latch *latch)
Definition: latch.c:505
void HandleWalSndInitStopping(void)
Definition: walsender.c:3017
static bool CheckProcSignal(ProcSignalReason reason)
Definition: procsignal.c:530
void HandleNotifyInterrupt(void)
Definition: async.c:1875
struct Latch * MyLatch
Definition: globals.c:54
void HandleParallelMessageInterrupt(void)
Definition: parallel.c:991
void latch_sigusr1_handler(void)
Definition: latch.c:1944
void HandleCatchupInterrupt(void)
Definition: sinval.c:156

◆ ProcSignalInit()

void ProcSignalInit ( int  pss_idx)

Definition at line 151 of file procsignal.c.

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

Referenced by AuxiliaryProcessMain(), and InitPostgres().

152 {
153  volatile ProcSignalSlot *slot;
154  uint64 barrier_generation;
155 
156  Assert(pss_idx >= 1 && pss_idx <= NumProcSignalSlots);
157 
158  slot = &ProcSignal->psh_slot[pss_idx - 1];
159 
160  /* sanity check */
161  if (slot->pss_pid != 0)
162  elog(LOG, "process %d taking over ProcSignal slot %d, but it's not empty",
163  MyProcPid, pss_idx);
164 
165  /* Clear out any leftover signal reasons */
166  MemSet(slot->pss_signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
167 
168  /*
169  * Initialize barrier state. Since we're a brand-new process, there
170  * shouldn't be any leftover backend-private state that needs to be
171  * updated. Therefore, we can broadcast the latest barrier generation and
172  * disregard any previously-set check bits.
173  *
174  * NB: This only works if this initialization happens early enough in the
175  * startup sequence that we haven't yet cached any state that might need
176  * to be invalidated. That's also why we have a memory barrier here, to be
177  * sure that any later reads of memory happen strictly after this.
178  */
180  barrier_generation =
182  pg_atomic_write_u64(&slot->pss_barrierGeneration, barrier_generation);
184 
185  /* Mark slot with my PID */
186  slot->pss_pid = MyProcPid;
187 
188  /* Remember slot location for CheckProcSignal */
189  MyProcSignalSlot = slot;
190 
191  /* Set up to release the slot on process exit */
193 }
int MyProcPid
Definition: globals.c:40
pg_atomic_uint64 psh_barrierGeneration
Definition: procsignal.c:75
#define MemSet(start, val, len)
Definition: c.h:1004
#define LOG
Definition: elog.h:26
pg_atomic_uint64 pss_barrierGeneration
Definition: procsignal.c:63
static void pg_atomic_write_u64(volatile pg_atomic_uint64 *ptr, uint64 val)
Definition: atomics.h:438
ProcSignalSlot psh_slot[FLEXIBLE_ARRAY_MEMBER]
Definition: procsignal.c:76
static void CleanupProcSignalState(int status, Datum arg)
Definition: procsignal.c:202
void on_shmem_exit(pg_on_exit_callback function, Datum arg)
Definition: ipc.c:361
pg_atomic_uint32 pss_barrierCheckMask
Definition: procsignal.c:64
static ProcSignalHeader * ProcSignal
Definition: procsignal.c:90
#define pg_memory_barrier()
Definition: atomics.h:145
#define Assert(condition)
Definition: c.h:800
#define Int32GetDatum(X)
Definition: postgres.h:479
static uint64 pg_atomic_read_u64(volatile pg_atomic_uint64 *ptr)
Definition: atomics.h:429
#define elog(elevel,...)
Definition: elog.h:228
sig_atomic_t pss_signalFlags[NUM_PROCSIGNALS]
Definition: procsignal.c:62
static volatile ProcSignalSlot * MyProcSignalSlot
Definition: procsignal.c:91
#define NumProcSignalSlots
Definition: procsignal.c:84
static void pg_atomic_write_u32(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: atomics.h:258

◆ ProcSignalShmemInit()

void ProcSignalShmemInit ( void  )

Definition at line 116 of file procsignal.c.

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

Referenced by CreateSharedMemoryAndSemaphores().

117 {
118  Size size = ProcSignalShmemSize();
119  bool found;
120 
122  ShmemInitStruct("ProcSignal", size, &found);
123 
124  /* If we're first, initialize. */
125  if (!found)
126  {
127  int i;
128 
130 
131  for (i = 0; i < NumProcSignalSlots; ++i)
132  {
133  ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
134 
135  slot->pss_pid = 0;
136  MemSet(slot->pss_signalFlags, 0, sizeof(slot->pss_signalFlags));
139  }
140  }
141 }
#define PG_UINT64_MAX
Definition: c.h:516
pg_atomic_uint64 psh_barrierGeneration
Definition: procsignal.c:75
#define MemSet(start, val, len)
Definition: c.h:1004
pg_atomic_uint64 pss_barrierGeneration
Definition: procsignal.c:63
ProcSignalSlot psh_slot[FLEXIBLE_ARRAY_MEMBER]
Definition: procsignal.c:76
static void pg_atomic_init_u64(volatile pg_atomic_uint64 *ptr, uint64 val)
Definition: atomics.h:415
void * ShmemInitStruct(const char *name, Size size, bool *foundPtr)
Definition: shmem.c:392
pg_atomic_uint32 pss_barrierCheckMask
Definition: procsignal.c:64
Size ProcSignalShmemSize(void)
Definition: procsignal.c:102
static ProcSignalHeader * ProcSignal
Definition: procsignal.c:90
size_t Size
Definition: c.h:528
int i
sig_atomic_t pss_signalFlags[NUM_PROCSIGNALS]
Definition: procsignal.c:62
#define NumProcSignalSlots
Definition: procsignal.c:84
static void pg_atomic_init_u32(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: atomics.h:223

◆ ProcSignalShmemSize()

Size ProcSignalShmemSize ( void  )

Definition at line 102 of file procsignal.c.

References add_size(), mul_size(), NumProcSignalSlots, and offsetof.

Referenced by CreateSharedMemoryAndSemaphores(), and ProcSignalShmemInit().

103 {
104  Size size;
105 
106  size = mul_size(NumProcSignalSlots, sizeof(ProcSignalSlot));
107  size = add_size(size, offsetof(ProcSignalHeader, psh_slot));
108  return size;
109 }
Size mul_size(Size s1, Size s2)
Definition: shmem.c:515
Size add_size(Size s1, Size s2)
Definition: shmem.c:498
size_t Size
Definition: c.h:528
#define NumProcSignalSlots
Definition: procsignal.c:84
#define offsetof(type, field)
Definition: c.h:723

◆ SendProcSignal()

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

Definition at line 250 of file procsignal.c.

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

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

251 {
252  volatile ProcSignalSlot *slot;
253 
254  if (backendId != InvalidBackendId)
255  {
256  slot = &ProcSignal->psh_slot[backendId - 1];
257 
258  /*
259  * Note: Since there's no locking, it's possible that the target
260  * process detaches from shared memory and exits right after this
261  * test, before we set the flag and send signal. And the signal slot
262  * might even be recycled by a new process, so it's remotely possible
263  * that we set a flag for a wrong process. That's OK, all the signals
264  * are such that no harm is done if they're mistakenly fired.
265  */
266  if (slot->pss_pid == pid)
267  {
268  /* Atomically set the proper flag */
269  slot->pss_signalFlags[reason] = true;
270  /* Send signal */
271  return kill(pid, SIGUSR1);
272  }
273  }
274  else
275  {
276  /*
277  * BackendId not provided, so search the array using pid. We search
278  * the array back to front so as to reduce search overhead. Passing
279  * InvalidBackendId means that the target is most likely an auxiliary
280  * process, which will have a slot near the end of the array.
281  */
282  int i;
283 
284  for (i = NumProcSignalSlots - 1; i >= 0; i--)
285  {
286  slot = &ProcSignal->psh_slot[i];
287 
288  if (slot->pss_pid == pid)
289  {
290  /* the above note about race conditions applies here too */
291 
292  /* Atomically set the proper flag */
293  slot->pss_signalFlags[reason] = true;
294  /* Send signal */
295  return kill(pid, SIGUSR1);
296  }
297  }
298  }
299 
300  errno = ESRCH;
301  return -1;
302 }
#define SIGUSR1
Definition: win32_port.h:171
#define kill(pid, sig)
Definition: win32_port.h:454
ProcSignalSlot psh_slot[FLEXIBLE_ARRAY_MEMBER]
Definition: procsignal.c:76
#define InvalidBackendId
Definition: backendid.h:23
static ProcSignalHeader * ProcSignal
Definition: procsignal.c:90
int i
sig_atomic_t pss_signalFlags[NUM_PROCSIGNALS]
Definition: procsignal.c:62
#define NumProcSignalSlots
Definition: procsignal.c:84

◆ WaitForProcSignalBarrier()

void WaitForProcSignalBarrier ( uint64  generation)

Definition at line 386 of file procsignal.c.

References Assert, CHECK_FOR_INTERRUPTS, i, Min, MyLatch, NumProcSignalSlots, pg_atomic_read_u64(), pg_memory_barrier, ProcSignalHeader::psh_barrierGeneration, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_barrierGeneration, ResetLatch(), WAIT_EVENT_PROC_SIGNAL_BARRIER, WaitLatch(), WL_EXIT_ON_PM_DEATH, WL_LATCH_SET, and WL_TIMEOUT.

387 {
388  long timeout = 125L;
389 
391 
392  for (int i = NumProcSignalSlots - 1; i >= 0; i--)
393  {
394  volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
395  uint64 oldval;
396 
397  oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
398  while (oldval < generation)
399  {
400  int events;
401 
403 
404  events =
409 
410  oldval = pg_atomic_read_u64(&slot->pss_barrierGeneration);
411  if (events & WL_TIMEOUT)
412  timeout = Min(timeout * 2, 1000L);
413  }
414  }
415 
416  /*
417  * The caller is probably calling this function because it wants to read
418  * the shared state or perform further writes to shared state once all
419  * backends are known to have absorbed the barrier. However, the read of
420  * pss_barrierGeneration was performed unlocked; insert a memory barrier
421  * to separate it from whatever follows.
422  */
424 }
#define WL_TIMEOUT
Definition: latch.h:127
pg_atomic_uint64 psh_barrierGeneration
Definition: procsignal.c:75
#define Min(x, y)
Definition: c.h:982
pg_atomic_uint64 pss_barrierGeneration
Definition: procsignal.c:63
void ResetLatch(Latch *latch)
Definition: latch.c:588
int WaitLatch(Latch *latch, int wakeEvents, long timeout, uint32 wait_event_info)
Definition: latch.c:390
ProcSignalSlot psh_slot[FLEXIBLE_ARRAY_MEMBER]
Definition: procsignal.c:76
static ProcSignalHeader * ProcSignal
Definition: procsignal.c:90
#define pg_memory_barrier()
Definition: atomics.h:145
#define Assert(condition)
Definition: c.h:800
static uint64 pg_atomic_read_u64(volatile pg_atomic_uint64 *ptr)
Definition: atomics.h:429
int i
#define NumProcSignalSlots
Definition: procsignal.c:84
struct Latch * MyLatch
Definition: globals.c:54
#define CHECK_FOR_INTERRUPTS()
Definition: miscadmin.h:99
#define WL_LATCH_SET
Definition: latch.h:124
#define WL_EXIT_ON_PM_DEATH
Definition: latch.h:129