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procsignal.c File Reference
#include "postgres.h"
#include <signal.h>
#include <unistd.h>
#include "access/parallel.h"
#include "commands/async.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "port/pg_bitutils.h"
#include "replication/logicalworker.h"
#include "replication/walsender.h"
#include "storage/condition_variable.h"
#include "storage/ipc.h"
#include "storage/latch.h"
#include "storage/shmem.h"
#include "storage/sinval.h"
#include "storage/smgr.h"
#include "tcop/tcopprot.h"
#include "utils/memutils.h"
Include dependency graph for procsignal.c:

Go to the source code of this file.

Data Structures

struct  ProcSignalSlot
 
struct  ProcSignalHeader
 

Macros

#define NumProcSignalSlots   (MaxBackends + NUM_AUXILIARY_PROCS)
 
#define BARRIER_SHOULD_CHECK(flags, type)    (((flags) & (((uint32) 1) << (uint32) (type))) != 0)
 
#define BARRIER_CLEAR_BIT(flags, type)    ((flags) &= ~(((uint32) 1) << (uint32) (type)))
 

Functions

static bool CheckProcSignal (ProcSignalReason reason)
 
static void CleanupProcSignalState (int status, Datum arg)
 
static void ResetProcSignalBarrierBits (uint32 flags)
 
Size ProcSignalShmemSize (void)
 
void ProcSignalShmemInit (void)
 
void ProcSignalInit (bool cancel_key_valid, int32 cancel_key)
 
int SendProcSignal (pid_t pid, ProcSignalReason reason, ProcNumber procNumber)
 
uint64 EmitProcSignalBarrier (ProcSignalBarrierType type)
 
void WaitForProcSignalBarrier (uint64 generation)
 
static void HandleProcSignalBarrierInterrupt (void)
 
void ProcessProcSignalBarrier (void)
 
void procsignal_sigusr1_handler (SIGNAL_ARGS)
 
void SendCancelRequest (int backendPID, int32 cancelAuthCode)
 

Variables

NON_EXEC_STATIC ProcSignalHeaderProcSignal = NULL
 
static ProcSignalSlotMyProcSignalSlot = NULL
 

Macro Definition Documentation

◆ BARRIER_CLEAR_BIT

#define BARRIER_CLEAR_BIT (   flags,
  type 
)     ((flags) &= ~(((uint32) 1) << (uint32) (type)))

Definition at line 101 of file procsignal.c.

◆ BARRIER_SHOULD_CHECK

#define BARRIER_SHOULD_CHECK (   flags,
  type 
)     (((flags) & (((uint32) 1) << (uint32) (type))) != 0)

Definition at line 97 of file procsignal.c.

◆ NumProcSignalSlots

#define NumProcSignalSlots   (MaxBackends + NUM_AUXILIARY_PROCS)

Definition at line 94 of file procsignal.c.

Function Documentation

◆ CheckProcSignal()

static bool CheckProcSignal ( ProcSignalReason  reason)
static

Definition at line 646 of file procsignal.c.

647{
648 volatile ProcSignalSlot *slot = MyProcSignalSlot;
649
650 if (slot != NULL)
651 {
652 /*
653 * Careful here --- don't clear flag if we haven't seen it set.
654 * pss_signalFlags is of type "volatile sig_atomic_t" to allow us to
655 * read it here safely, without holding the spinlock.
656 */
657 if (slot->pss_signalFlags[reason])
658 {
659 slot->pss_signalFlags[reason] = false;
660 return true;
661 }
662 }
663
664 return false;
665}
static ProcSignalSlot * MyProcSignalSlot
Definition: procsignal.c:105
volatile sig_atomic_t pss_signalFlags[NUM_PROCSIGNALS]
Definition: procsignal.c:68

References MyProcSignalSlot, and ProcSignalSlot::pss_signalFlags.

Referenced by procsignal_sigusr1_handler().

◆ CleanupProcSignalState()

static void CleanupProcSignalState ( int  status,
Datum  arg 
)
static

Definition at line 225 of file procsignal.c.

226{
227 pid_t old_pid;
229
230 /*
231 * Clear MyProcSignalSlot, so that a SIGUSR1 received after this point
232 * won't try to access it after it's no longer ours (and perhaps even
233 * after we've unmapped the shared memory segment).
234 */
235 Assert(MyProcSignalSlot != NULL);
236 MyProcSignalSlot = NULL;
237
238 /* sanity check */
240 old_pid = pg_atomic_read_u32(&slot->pss_pid);
241 if (old_pid != MyProcPid)
242 {
243 /*
244 * don't ERROR here. We're exiting anyway, and don't want to get into
245 * infinite loop trying to exit
246 */
248 elog(LOG, "process %d releasing ProcSignal slot %d, but it contains %d",
249 MyProcPid, (int) (slot - ProcSignal->psh_slot), (int) old_pid);
250 return; /* XXX better to zero the slot anyway? */
251 }
252
253 /* Mark the slot as unused */
254 pg_atomic_write_u32(&slot->pss_pid, 0);
255 slot->pss_cancel_key_valid = false;
256 slot->pss_cancel_key = 0;
257
258 /*
259 * Make this slot look like it's absorbed all possible barriers, so that
260 * no barrier waits block on it.
261 */
263
265
267}
static void pg_atomic_write_u64(volatile pg_atomic_uint64 *ptr, uint64 val)
Definition: atomics.h:485
static void pg_atomic_write_u32(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: atomics.h:276
static uint32 pg_atomic_read_u32(volatile pg_atomic_uint32 *ptr)
Definition: atomics.h:239
#define Assert(condition)
Definition: c.h:812
#define PG_UINT64_MAX
Definition: c.h:547
void ConditionVariableBroadcast(ConditionVariable *cv)
#define LOG
Definition: elog.h:31
#define elog(elevel,...)
Definition: elog.h:225
int MyProcPid
Definition: globals.c:46
NON_EXEC_STATIC ProcSignalHeader * ProcSignal
Definition: procsignal.c:104
#define SpinLockRelease(lock)
Definition: spin.h:61
#define SpinLockAcquire(lock)
Definition: spin.h:59
ProcSignalSlot psh_slot[FLEXIBLE_ARRAY_MEMBER]
Definition: procsignal.c:86
int32 pss_cancel_key
Definition: procsignal.c:67
ConditionVariable pss_barrierCV
Definition: procsignal.c:74
pg_atomic_uint64 pss_barrierGeneration
Definition: procsignal.c:72
bool pss_cancel_key_valid
Definition: procsignal.c:66
slock_t pss_mutex
Definition: procsignal.c:69
pg_atomic_uint32 pss_pid
Definition: procsignal.c:65

References Assert, ConditionVariableBroadcast(), elog, LOG, MyProcPid, MyProcSignalSlot, pg_atomic_read_u32(), pg_atomic_write_u32(), pg_atomic_write_u64(), PG_UINT64_MAX, ProcSignal, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_barrierCV, ProcSignalSlot::pss_barrierGeneration, ProcSignalSlot::pss_cancel_key, ProcSignalSlot::pss_cancel_key_valid, ProcSignalSlot::pss_mutex, ProcSignalSlot::pss_pid, SpinLockAcquire, and SpinLockRelease.

Referenced by ProcSignalInit().

◆ EmitProcSignalBarrier()

uint64 EmitProcSignalBarrier ( ProcSignalBarrierType  type)

Definition at line 353 of file procsignal.c.

354{
355 uint32 flagbit = 1 << (uint32) type;
356 uint64 generation;
357
358 /*
359 * Set all the flags.
360 *
361 * Note that pg_atomic_fetch_or_u32 has full barrier semantics, so this is
362 * totally ordered with respect to anything the caller did before, and
363 * anything that we do afterwards. (This is also true of the later call to
364 * pg_atomic_add_fetch_u64.)
365 */
366 for (int i = 0; i < NumProcSignalSlots; i++)
367 {
368 volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
369
371 }
372
373 /*
374 * Increment the generation counter.
375 */
376 generation =
378
379 /*
380 * Signal all the processes, so that they update their advertised barrier
381 * generation.
382 *
383 * Concurrency is not a problem here. Backends that have exited don't
384 * matter, and new backends that have joined since we entered this
385 * function must already have current state, since the caller is
386 * responsible for making sure that the relevant state is entirely visible
387 * before calling this function in the first place. We still have to wake
388 * them up - because we can't distinguish between such backends and older
389 * backends that need to update state - but they won't actually need to
390 * change any state.
391 */
392 for (int i = NumProcSignalSlots - 1; i >= 0; i--)
393 {
394 volatile ProcSignalSlot *slot = &ProcSignal->psh_slot[i];
395 pid_t pid = pg_atomic_read_u32(&slot->pss_pid);
396
397 if (pid != 0)
398 {
400 pid = pg_atomic_read_u32(&slot->pss_pid);
401 if (pid != 0)
402 {
403 /* see SendProcSignal for details */
404 slot->pss_signalFlags[PROCSIG_BARRIER] = true;
406 kill(pid, SIGUSR1);
407 }
408 else
410 }
411 }
412
413 return generation;
414}
static uint32 pg_atomic_fetch_or_u32(volatile pg_atomic_uint32 *ptr, uint32 or_)
Definition: atomics.h:410
static uint64 pg_atomic_add_fetch_u64(volatile pg_atomic_uint64 *ptr, int64 add_)
Definition: atomics.h:559
uint64_t uint64
Definition: c.h:486
uint32_t uint32
Definition: c.h:485
int i
Definition: isn.c:72
#define NumProcSignalSlots
Definition: procsignal.c:94
@ PROCSIG_BARRIER
Definition: procsignal.h:36
pg_atomic_uint64 psh_barrierGeneration
Definition: procsignal.c:85
pg_atomic_uint32 pss_barrierCheckMask
Definition: procsignal.c:73
const char * type
#define kill(pid, sig)
Definition: win32_port.h:503
#define SIGUSR1
Definition: win32_port.h:180

References i, kill, NumProcSignalSlots, pg_atomic_add_fetch_u64(), pg_atomic_fetch_or_u32(), pg_atomic_read_u32(), PROCSIG_BARRIER, ProcSignal, ProcSignalHeader::psh_barrierGeneration, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_barrierCheckMask, ProcSignalSlot::pss_mutex, ProcSignalSlot::pss_pid, ProcSignalSlot::pss_signalFlags, SIGUSR1, SpinLockAcquire, SpinLockRelease, and type.

Referenced by dbase_redo(), dropdb(), DropTableSpace(), movedb(), and tblspc_redo().

◆ HandleProcSignalBarrierInterrupt()

static void HandleProcSignalBarrierInterrupt ( void  )
static

Definition at line 480 of file procsignal.c.

481{
482 InterruptPending = true;
484 /* latch will be set by procsignal_sigusr1_handler */
485}
volatile sig_atomic_t ProcSignalBarrierPending
Definition: globals.c:39
volatile sig_atomic_t InterruptPending
Definition: globals.c:31

References InterruptPending, and ProcSignalBarrierPending.

Referenced by procsignal_sigusr1_handler().

◆ ProcessProcSignalBarrier()

void ProcessProcSignalBarrier ( void  )

Definition at line 496 of file procsignal.c.

497{
498 uint64 local_gen;
499 uint64 shared_gen;
500 volatile uint32 flags;
501
503
504 /* Exit quickly if there's no work to do. */
506 return;
508
509 /*
510 * It's not unlikely to process multiple barriers at once, before the
511 * signals for all the barriers have arrived. To avoid unnecessary work in
512 * response to subsequent signals, exit early if we already have processed
513 * all of them.
514 */
517
518 Assert(local_gen <= shared_gen);
519
520 if (local_gen == shared_gen)
521 return;
522
523 /*
524 * Get and clear the flags that are set for this backend. Note that
525 * pg_atomic_exchange_u32 is a full barrier, so we're guaranteed that the
526 * read of the barrier generation above happens before we atomically
527 * extract the flags, and that any subsequent state changes happen
528 * afterward.
529 *
530 * NB: In order to avoid race conditions, we must zero
531 * pss_barrierCheckMask first and only afterwards try to do barrier
532 * processing. If we did it in the other order, someone could send us
533 * another barrier of some type right after we called the
534 * barrier-processing function but before we cleared the bit. We would
535 * have no way of knowing that the bit needs to stay set in that case, so
536 * the need to call the barrier-processing function again would just get
537 * forgotten. So instead, we tentatively clear all the bits and then put
538 * back any for which we don't manage to successfully absorb the barrier.
539 */
541
542 /*
543 * If there are no flags set, then we can skip doing any real work.
544 * Otherwise, establish a PG_TRY block, so that we don't lose track of
545 * which types of barrier processing are needed if an ERROR occurs.
546 */
547 if (flags != 0)
548 {
549 bool success = true;
550
551 PG_TRY();
552 {
553 /*
554 * Process each type of barrier. The barrier-processing functions
555 * should normally return true, but may return false if the
556 * barrier can't be absorbed at the current time. This should be
557 * rare, because it's pretty expensive. Every single
558 * CHECK_FOR_INTERRUPTS() will return here until we manage to
559 * absorb the barrier, and that cost will add up in a hurry.
560 *
561 * NB: It ought to be OK to call the barrier-processing functions
562 * unconditionally, but it's more efficient to call only the ones
563 * that might need us to do something based on the flags.
564 */
565 while (flags != 0)
566 {
568 bool processed = true;
569
571 switch (type)
572 {
574 processed = ProcessBarrierSmgrRelease();
575 break;
576 }
577
578 /*
579 * To avoid an infinite loop, we must always unset the bit in
580 * flags.
581 */
582 BARRIER_CLEAR_BIT(flags, type);
583
584 /*
585 * If we failed to process the barrier, reset the shared bit
586 * so we try again later, and set a flag so that we don't bump
587 * our generation.
588 */
589 if (!processed)
590 {
592 success = false;
593 }
594 }
595 }
596 PG_CATCH();
597 {
598 /*
599 * If an ERROR occurred, we'll need to try again later to handle
600 * that barrier type and any others that haven't been handled yet
601 * or weren't successfully absorbed.
602 */
604 PG_RE_THROW();
605 }
606 PG_END_TRY();
607
608 /*
609 * If some barrier types were not successfully absorbed, we will have
610 * to try again later.
611 */
612 if (!success)
613 return;
614 }
615
616 /*
617 * State changes related to all types of barriers that might have been
618 * emitted have now been handled, so we can update our notion of the
619 * generation to the one we observed before beginning the updates. If
620 * things have changed further, it'll get fixed up when this function is
621 * next called.
622 */
625}
static uint32 pg_atomic_exchange_u32(volatile pg_atomic_uint32 *ptr, uint32 newval)
Definition: atomics.h:330
static uint64 pg_atomic_read_u64(volatile pg_atomic_uint64 *ptr)
Definition: atomics.h:467
#define PG_RE_THROW()
Definition: elog.h:412
#define PG_TRY(...)
Definition: elog.h:371
#define PG_END_TRY(...)
Definition: elog.h:396
#define PG_CATCH(...)
Definition: elog.h:381
static bool success
Definition: initdb.c:186
static int pg_rightmost_one_pos32(uint32 word)
Definition: pg_bitutils.h:111
static void ResetProcSignalBarrierBits(uint32 flags)
Definition: procsignal.c:633
#define BARRIER_CLEAR_BIT(flags, type)
Definition: procsignal.c:101
ProcSignalBarrierType
Definition: procsignal.h:55
@ PROCSIGNAL_BARRIER_SMGRRELEASE
Definition: procsignal.h:56
bool ProcessBarrierSmgrRelease(void)
Definition: smgr.c:845

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, ProcessBarrierSmgrRelease(), ProcSignal, PROCSIGNAL_BARRIER_SMGRRELEASE, ProcSignalBarrierPending, ProcSignalHeader::psh_barrierGeneration, ProcSignalSlot::pss_barrierCheckMask, ProcSignalSlot::pss_barrierCV, ProcSignalSlot::pss_barrierGeneration, ResetProcSignalBarrierBits(), success, and type.

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

◆ procsignal_sigusr1_handler()

void procsignal_sigusr1_handler ( SIGNAL_ARGS  )

Definition at line 671 of file procsignal.c.

672{
675
678
681
684
687
690
693
696
699
702
705
708
711
714
716}
void HandleParallelApplyMessageInterrupt(void)
void HandleNotifyInterrupt(void)
Definition: async.c:1804
void HandleParallelMessageInterrupt(void)
Definition: parallel.c:1033
struct Latch * MyLatch
Definition: globals.c:62
void SetLatch(Latch *latch)
Definition: latch.c:632
void HandleLogMemoryContextInterrupt(void)
Definition: mcxt.c:1272
void HandleRecoveryConflictInterrupt(ProcSignalReason reason)
Definition: postgres.c:3064
static bool CheckProcSignal(ProcSignalReason reason)
Definition: procsignal.c:646
static void HandleProcSignalBarrierInterrupt(void)
Definition: procsignal.c:480
@ PROCSIG_PARALLEL_MESSAGE
Definition: procsignal.h:34
@ PROCSIG_RECOVERY_CONFLICT_BUFFERPIN
Definition: procsignal.h:47
@ PROCSIG_CATCHUP_INTERRUPT
Definition: procsignal.h:32
@ PROCSIG_RECOVERY_CONFLICT_LOCK
Definition: procsignal.h:44
@ PROCSIG_LOG_MEMORY_CONTEXT
Definition: procsignal.h:37
@ PROCSIG_RECOVERY_CONFLICT_LOGICALSLOT
Definition: procsignal.h:46
@ PROCSIG_RECOVERY_CONFLICT_DATABASE
Definition: procsignal.h:42
@ PROCSIG_WALSND_INIT_STOPPING
Definition: procsignal.h:35
@ PROCSIG_PARALLEL_APPLY_MESSAGE
Definition: procsignal.h:38
@ PROCSIG_RECOVERY_CONFLICT_SNAPSHOT
Definition: procsignal.h:45
@ PROCSIG_NOTIFY_INTERRUPT
Definition: procsignal.h:33
@ PROCSIG_RECOVERY_CONFLICT_TABLESPACE
Definition: procsignal.h:43
@ PROCSIG_RECOVERY_CONFLICT_STARTUP_DEADLOCK
Definition: procsignal.h:48
void HandleCatchupInterrupt(void)
Definition: sinval.c:154
void HandleWalSndInitStopping(void)
Definition: walsender.c:3533

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

Referenced by autoprewarm_main(), AutoVacWorkerMain(), BackgroundWorkerMain(), BackgroundWriterMain(), CheckpointerMain(), PgArchiverMain(), PostgresMain(), ReplSlotSyncWorkerMain(), StartupProcessMain(), WalReceiverMain(), WalSndSignals(), WalSummarizerMain(), and WalWriterMain().

◆ ProcSignalInit()

void ProcSignalInit ( bool  cancel_key_valid,
int32  cancel_key 
)

Definition at line 166 of file procsignal.c.

167{
168 ProcSignalSlot *slot;
169 uint64 barrier_generation;
170
171 if (MyProcNumber < 0)
172 elog(ERROR, "MyProcNumber not set");
174 elog(ERROR, "unexpected MyProcNumber %d in ProcSignalInit (max %d)", MyProcNumber, NumProcSignalSlots);
176
177 /* sanity check */
179 if (pg_atomic_read_u32(&slot->pss_pid) != 0)
180 {
182 elog(LOG, "process %d taking over ProcSignal slot %d, but it's not empty",
184 }
185
186 /* Clear out any leftover signal reasons */
187 MemSet(slot->pss_signalFlags, 0, NUM_PROCSIGNALS * sizeof(sig_atomic_t));
188
189 /*
190 * Initialize barrier state. Since we're a brand-new process, there
191 * shouldn't be any leftover backend-private state that needs to be
192 * updated. Therefore, we can broadcast the latest barrier generation and
193 * disregard any previously-set check bits.
194 *
195 * NB: This only works if this initialization happens early enough in the
196 * startup sequence that we haven't yet cached any state that might need
197 * to be invalidated. That's also why we have a memory barrier here, to be
198 * sure that any later reads of memory happen strictly after this.
199 */
201 barrier_generation =
203 pg_atomic_write_u64(&slot->pss_barrierGeneration, barrier_generation);
204
205 slot->pss_cancel_key_valid = cancel_key_valid;
206 slot->pss_cancel_key = cancel_key;
208
210
211 /* Remember slot location for CheckProcSignal */
212 MyProcSignalSlot = slot;
213
214 /* Set up to release the slot on process exit */
216}
#define MemSet(start, val, len)
Definition: c.h:974
#define ERROR
Definition: elog.h:39
ProcNumber MyProcNumber
Definition: globals.c:89
void on_shmem_exit(pg_on_exit_callback function, Datum arg)
Definition: ipc.c:365
uintptr_t Datum
Definition: postgres.h:64
static void CleanupProcSignalState(int status, Datum arg)
Definition: procsignal.c:225
#define NUM_PROCSIGNALS
Definition: procsignal.h:52

References CleanupProcSignalState(), elog, ERROR, LOG, MemSet, MyProcNumber, MyProcPid, MyProcSignalSlot, NUM_PROCSIGNALS, NumProcSignalSlots, on_shmem_exit(), pg_atomic_read_u32(), pg_atomic_read_u64(), pg_atomic_write_u32(), pg_atomic_write_u64(), ProcSignal, ProcSignalHeader::psh_barrierGeneration, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_barrierCheckMask, ProcSignalSlot::pss_barrierGeneration, ProcSignalSlot::pss_cancel_key, ProcSignalSlot::pss_cancel_key_valid, ProcSignalSlot::pss_mutex, ProcSignalSlot::pss_pid, ProcSignalSlot::pss_signalFlags, SpinLockAcquire, and SpinLockRelease.

Referenced by AuxiliaryProcessMainCommon(), and InitPostgres().

◆ ProcSignalShmemInit()

void ProcSignalShmemInit ( void  )

Definition at line 130 of file procsignal.c.

131{
133 bool found;
134
136 ShmemInitStruct("ProcSignal", size, &found);
137
138 /* If we're first, initialize. */
139 if (!found)
140 {
141 int i;
142
144
145 for (i = 0; i < NumProcSignalSlots; ++i)
146 {
148
149 SpinLockInit(&slot->pss_mutex);
150 pg_atomic_init_u32(&slot->pss_pid, 0);
151 slot->pss_cancel_key_valid = false;
152 slot->pss_cancel_key = 0;
153 MemSet(slot->pss_signalFlags, 0, sizeof(slot->pss_signalFlags));
157 }
158 }
159}
static void pg_atomic_init_u32(volatile pg_atomic_uint32 *ptr, uint32 val)
Definition: atomics.h:221
static void pg_atomic_init_u64(volatile pg_atomic_uint64 *ptr, uint64 val)
Definition: atomics.h:453
size_t Size
Definition: c.h:559
void ConditionVariableInit(ConditionVariable *cv)
Size ProcSignalShmemSize(void)
Definition: procsignal.c:116
void * ShmemInitStruct(const char *name, Size size, bool *foundPtr)
Definition: shmem.c:382
static pg_noinline void Size size
Definition: slab.c:607
#define SpinLockInit(lock)
Definition: spin.h:57

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_cancel_key, ProcSignalSlot::pss_cancel_key_valid, ProcSignalSlot::pss_mutex, ProcSignalSlot::pss_pid, ProcSignalSlot::pss_signalFlags, ShmemInitStruct(), size, and SpinLockInit.

Referenced by CreateOrAttachShmemStructs().

◆ ProcSignalShmemSize()

Size ProcSignalShmemSize ( void  )

Definition at line 116 of file procsignal.c.

117{
118 Size size;
119
121 size = add_size(size, offsetof(ProcSignalHeader, psh_slot));
122 return size;
123}
Size add_size(Size s1, Size s2)
Definition: shmem.c:488
Size mul_size(Size s1, Size s2)
Definition: shmem.c:505

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

Referenced by CalculateShmemSize(), and ProcSignalShmemInit().

◆ ResetProcSignalBarrierBits()

static void ResetProcSignalBarrierBits ( uint32  flags)
static

◆ SendCancelRequest()

void SendCancelRequest ( int  backendPID,
int32  cancelAuthCode 
)

Definition at line 726 of file procsignal.c.

727{
728 Assert(backendPID != 0);
729
730 /*
731 * See if we have a matching backend. Reading the pss_pid and
732 * pss_cancel_key fields is racy, a backend might die and remove itself
733 * from the array at any time. The probability of the cancellation key
734 * matching wrong process is miniscule, however, so we can live with that.
735 * PIDs are reused too, so sending the signal based on PID is inherently
736 * racy anyway, although OS's avoid reusing PIDs too soon.
737 */
738 for (int i = 0; i < NumProcSignalSlots; i++)
739 {
741 bool match;
742
743 if (pg_atomic_read_u32(&slot->pss_pid) != backendPID)
744 continue;
745
746 /* Acquire the spinlock and re-check */
748 if (pg_atomic_read_u32(&slot->pss_pid) != backendPID)
749 {
751 continue;
752 }
753 else
754 {
755 match = slot->pss_cancel_key_valid && slot->pss_cancel_key == cancelAuthCode;
756
758
759 if (match)
760 {
761 /* Found a match; signal that backend to cancel current op */
763 (errmsg_internal("processing cancel request: sending SIGINT to process %d",
764 backendPID)));
765
766 /*
767 * If we have setsid(), signal the backend's whole process
768 * group
769 */
770#ifdef HAVE_SETSID
771 kill(-backendPID, SIGINT);
772#else
773 kill(backendPID, SIGINT);
774#endif
775 }
776 else
777 {
778 /* Right PID, wrong key: no way, Jose */
779 ereport(LOG,
780 (errmsg("wrong key in cancel request for process %d",
781 backendPID)));
782 }
783 return;
784 }
785 }
786
787 /* No matching backend */
788 ereport(LOG,
789 (errmsg("PID %d in cancel request did not match any process",
790 backendPID)));
791}
int errmsg_internal(const char *fmt,...)
Definition: elog.c:1157
int errmsg(const char *fmt,...)
Definition: elog.c:1070
#define DEBUG2
Definition: elog.h:29
#define ereport(elevel,...)
Definition: elog.h:149

References Assert, DEBUG2, ereport, errmsg(), errmsg_internal(), i, kill, LOG, NumProcSignalSlots, pg_atomic_read_u32(), ProcSignal, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_cancel_key, ProcSignalSlot::pss_cancel_key_valid, ProcSignalSlot::pss_mutex, ProcSignalSlot::pss_pid, SpinLockAcquire, and SpinLockRelease.

Referenced by ProcessStartupPacket().

◆ SendProcSignal()

int SendProcSignal ( pid_t  pid,
ProcSignalReason  reason,
ProcNumber  procNumber 
)

Definition at line 281 of file procsignal.c.

282{
283 volatile ProcSignalSlot *slot;
284
285 if (procNumber != INVALID_PROC_NUMBER)
286 {
287 Assert(procNumber < NumProcSignalSlots);
288 slot = &ProcSignal->psh_slot[procNumber];
289
291 if (pg_atomic_read_u32(&slot->pss_pid) == pid)
292 {
293 /* Atomically set the proper flag */
294 slot->pss_signalFlags[reason] = true;
296 /* Send signal */
297 return kill(pid, SIGUSR1);
298 }
300 }
301 else
302 {
303 /*
304 * procNumber not provided, so search the array using pid. We search
305 * the array back to front so as to reduce search overhead. Passing
306 * INVALID_PROC_NUMBER means that the target is most likely an
307 * auxiliary process, which will have a slot near the end of the
308 * array.
309 */
310 int i;
311
312 for (i = NumProcSignalSlots - 1; i >= 0; i--)
313 {
314 slot = &ProcSignal->psh_slot[i];
315
316 if (pg_atomic_read_u32(&slot->pss_pid) == pid)
317 {
319 if (pg_atomic_read_u32(&slot->pss_pid) == pid)
320 {
321 /* Atomically set the proper flag */
322 slot->pss_signalFlags[reason] = true;
324 /* Send signal */
325 return kill(pid, SIGUSR1);
326 }
328 }
329 }
330 }
331
332 errno = ESRCH;
333 return -1;
334}
#define INVALID_PROC_NUMBER
Definition: procnumber.h:26

References Assert, i, INVALID_PROC_NUMBER, kill, NumProcSignalSlots, pg_atomic_read_u32(), ProcSignal, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_mutex, ProcSignalSlot::pss_pid, ProcSignalSlot::pss_signalFlags, SIGUSR1, SpinLockAcquire, and SpinLockRelease.

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

◆ WaitForProcSignalBarrier()

void WaitForProcSignalBarrier ( uint64  generation)

Definition at line 421 of file procsignal.c.

422{
424
425 elog(DEBUG1,
426 "waiting for all backends to process ProcSignalBarrier generation "
428 generation);
429
430 for (int i = NumProcSignalSlots - 1; i >= 0; i--)
431 {
433 uint64 oldval;
434
435 /*
436 * It's important that we check only pss_barrierGeneration here and
437 * not pss_barrierCheckMask. Bits in pss_barrierCheckMask get cleared
438 * before the barrier is actually absorbed, but pss_barrierGeneration
439 * is updated only afterward.
440 */
442 while (oldval < generation)
443 {
445 5000,
446 WAIT_EVENT_PROC_SIGNAL_BARRIER))
447 ereport(LOG,
448 (errmsg("still waiting for backend with PID %d to accept ProcSignalBarrier",
449 (int) pg_atomic_read_u32(&slot->pss_pid))));
451 }
453 }
454
455 elog(DEBUG1,
456 "finished waiting for all backends to process ProcSignalBarrier generation "
458 generation);
459
460 /*
461 * The caller is probably calling this function because it wants to read
462 * the shared state or perform further writes to shared state once all
463 * backends are known to have absorbed the barrier. However, the read of
464 * pss_barrierGeneration was performed unlocked; insert a memory barrier
465 * to separate it from whatever follows.
466 */
468}
#define pg_memory_barrier()
Definition: atomics.h:143
#define UINT64_FORMAT
Definition: c.h:504
bool ConditionVariableCancelSleep(void)
bool ConditionVariableTimedSleep(ConditionVariable *cv, long timeout, uint32 wait_event_info)
#define DEBUG1
Definition: elog.h:30

References Assert, ConditionVariableCancelSleep(), ConditionVariableTimedSleep(), DEBUG1, elog, ereport, errmsg(), i, LOG, NumProcSignalSlots, pg_atomic_read_u32(), pg_atomic_read_u64(), pg_memory_barrier, ProcSignal, ProcSignalHeader::psh_barrierGeneration, ProcSignalHeader::psh_slot, ProcSignalSlot::pss_barrierCV, ProcSignalSlot::pss_barrierGeneration, ProcSignalSlot::pss_pid, and UINT64_FORMAT.

Referenced by dbase_redo(), dropdb(), DropTableSpace(), movedb(), and tblspc_redo().

Variable Documentation

◆ MyProcSignalSlot

◆ ProcSignal