1670 lines
50 KiB
C
1670 lines
50 KiB
C
/*-------------------------------------------------------------------------
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*
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* proc.c
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* routines to manage per-process shared memory data structure
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*
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* Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/backend/storage/lmgr/proc.c
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* Interface (a):
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* ProcSleep(), ProcWakeup(),
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* ProcQueueAlloc() -- create a shm queue for sleeping processes
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* ProcQueueInit() -- create a queue without allocing memory
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*
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* Waiting for a lock causes the backend to be put to sleep. Whoever releases
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* the lock wakes the process up again (and gives it an error code so it knows
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* whether it was awoken on an error condition).
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*
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* Interface (b):
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*
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* ProcReleaseLocks -- frees the locks associated with current transaction
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*
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* ProcKill -- destroys the shared memory state (and locks)
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* associated with the process.
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*/
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#include "postgres.h"
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#include <signal.h>
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#include <unistd.h>
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#include <sys/time.h>
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#include "access/transam.h"
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#include "access/twophase.h"
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#include "access/xact.h"
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#include "miscadmin.h"
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#include "postmaster/autovacuum.h"
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#include "replication/slot.h"
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#include "replication/syncrep.h"
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#include "storage/ipc.h"
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#include "storage/lmgr.h"
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#include "storage/pmsignal.h"
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#include "storage/proc.h"
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#include "storage/procarray.h"
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#include "storage/procsignal.h"
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#include "storage/spin.h"
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#include "utils/timeout.h"
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#include "utils/timestamp.h"
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/* GUC variables */
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int DeadlockTimeout = 1000;
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int StatementTimeout = 0;
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int LockTimeout = 0;
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bool log_lock_waits = false;
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/* Pointer to this process's PGPROC and PGXACT structs, if any */
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PGPROC *MyProc = NULL;
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PGXACT *MyPgXact = NULL;
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/*
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* This spinlock protects the freelist of recycled PGPROC structures.
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* We cannot use an LWLock because the LWLock manager depends on already
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* having a PGPROC and a wait semaphore! But these structures are touched
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* relatively infrequently (only at backend startup or shutdown) and not for
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* very long, so a spinlock is okay.
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*/
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NON_EXEC_STATIC slock_t *ProcStructLock = NULL;
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/* Pointers to shared-memory structures */
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PROC_HDR *ProcGlobal = NULL;
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NON_EXEC_STATIC PGPROC *AuxiliaryProcs = NULL;
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PGPROC *PreparedXactProcs = NULL;
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/* If we are waiting for a lock, this points to the associated LOCALLOCK */
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static LOCALLOCK *lockAwaited = NULL;
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/* Mark this volatile because it can be changed by signal handler */
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static volatile DeadLockState deadlock_state = DS_NOT_YET_CHECKED;
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static void RemoveProcFromArray(int code, Datum arg);
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static void ProcKill(int code, Datum arg);
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static void AuxiliaryProcKill(int code, Datum arg);
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/*
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* Report shared-memory space needed by InitProcGlobal.
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*/
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Size
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ProcGlobalShmemSize(void)
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{
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Size size = 0;
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/* ProcGlobal */
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size = add_size(size, sizeof(PROC_HDR));
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/* MyProcs, including autovacuum workers and launcher */
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size = add_size(size, mul_size(MaxBackends, sizeof(PGPROC)));
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/* AuxiliaryProcs */
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size = add_size(size, mul_size(NUM_AUXILIARY_PROCS, sizeof(PGPROC)));
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/* Prepared xacts */
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size = add_size(size, mul_size(max_prepared_xacts, sizeof(PGPROC)));
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/* ProcStructLock */
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size = add_size(size, sizeof(slock_t));
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size = add_size(size, mul_size(MaxBackends, sizeof(PGXACT)));
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size = add_size(size, mul_size(NUM_AUXILIARY_PROCS, sizeof(PGXACT)));
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size = add_size(size, mul_size(max_prepared_xacts, sizeof(PGXACT)));
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return size;
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}
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/*
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* Report number of semaphores needed by InitProcGlobal.
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*/
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int
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ProcGlobalSemas(void)
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{
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/*
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* We need a sema per backend (including autovacuum), plus one for each
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* auxiliary process.
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*/
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return MaxBackends + NUM_AUXILIARY_PROCS;
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}
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/*
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* InitProcGlobal -
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* Initialize the global process table during postmaster or standalone
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* backend startup.
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*
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* We also create all the per-process semaphores we will need to support
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* the requested number of backends. We used to allocate semaphores
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* only when backends were actually started up, but that is bad because
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* it lets Postgres fail under load --- a lot of Unix systems are
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* (mis)configured with small limits on the number of semaphores, and
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* running out when trying to start another backend is a common failure.
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* So, now we grab enough semaphores to support the desired max number
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* of backends immediately at initialization --- if the sysadmin has set
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* MaxConnections, max_worker_processes, or autovacuum_max_workers higher
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* than his kernel will support, he'll find out sooner rather than later.
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*
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* Another reason for creating semaphores here is that the semaphore
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* implementation typically requires us to create semaphores in the
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* postmaster, not in backends.
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*
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* Note: this is NOT called by individual backends under a postmaster,
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* not even in the EXEC_BACKEND case. The ProcGlobal and AuxiliaryProcs
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* pointers must be propagated specially for EXEC_BACKEND operation.
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*/
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void
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InitProcGlobal(void)
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{
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PGPROC *procs;
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PGXACT *pgxacts;
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int i,
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j;
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bool found;
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uint32 TotalProcs = MaxBackends + NUM_AUXILIARY_PROCS + max_prepared_xacts;
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/* Create the ProcGlobal shared structure */
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ProcGlobal = (PROC_HDR *)
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ShmemInitStruct("Proc Header", sizeof(PROC_HDR), &found);
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Assert(!found);
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/*
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* Initialize the data structures.
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*/
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ProcGlobal->spins_per_delay = DEFAULT_SPINS_PER_DELAY;
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ProcGlobal->freeProcs = NULL;
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ProcGlobal->autovacFreeProcs = NULL;
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ProcGlobal->bgworkerFreeProcs = NULL;
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ProcGlobal->startupProc = NULL;
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ProcGlobal->startupProcPid = 0;
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ProcGlobal->startupBufferPinWaitBufId = -1;
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ProcGlobal->walwriterLatch = NULL;
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ProcGlobal->checkpointerLatch = NULL;
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/*
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* Create and initialize all the PGPROC structures we'll need. There are
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* five separate consumers: (1) normal backends, (2) autovacuum workers
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* and the autovacuum launcher, (3) background workers, (4) auxiliary
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* processes, and (5) prepared transactions. Each PGPROC structure is
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* dedicated to exactly one of these purposes, and they do not move
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* between groups.
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*/
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procs = (PGPROC *) ShmemAlloc(TotalProcs * sizeof(PGPROC));
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ProcGlobal->allProcs = procs;
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/* XXX allProcCount isn't really all of them; it excludes prepared xacts */
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ProcGlobal->allProcCount = MaxBackends + NUM_AUXILIARY_PROCS;
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if (!procs)
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ereport(FATAL,
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(errcode(ERRCODE_OUT_OF_MEMORY),
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errmsg("out of shared memory")));
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MemSet(procs, 0, TotalProcs * sizeof(PGPROC));
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/*
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* Also allocate a separate array of PGXACT structures. This is separate
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* from the main PGPROC array so that the most heavily accessed data is
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* stored contiguously in memory in as few cache lines as possible. This
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* provides significant performance benefits, especially on a
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* multiprocessor system. There is one PGXACT structure for every PGPROC
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* structure.
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*/
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pgxacts = (PGXACT *) ShmemAlloc(TotalProcs * sizeof(PGXACT));
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MemSet(pgxacts, 0, TotalProcs * sizeof(PGXACT));
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ProcGlobal->allPgXact = pgxacts;
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for (i = 0; i < TotalProcs; i++)
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{
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/* Common initialization for all PGPROCs, regardless of type. */
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/*
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* Set up per-PGPROC semaphore, latch, and backendLock. Prepared xact
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* dummy PGPROCs don't need these though - they're never associated
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* with a real process
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*/
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if (i < MaxBackends + NUM_AUXILIARY_PROCS)
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{
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PGSemaphoreCreate(&(procs[i].sem));
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InitSharedLatch(&(procs[i].procLatch));
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procs[i].backendLock = LWLockAssign();
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}
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procs[i].pgprocno = i;
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/*
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* Newly created PGPROCs for normal backends, autovacuum and bgworkers
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* must be queued up on the appropriate free list. Because there can
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* only ever be a small, fixed number of auxiliary processes, no free
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* list is used in that case; InitAuxiliaryProcess() instead uses a
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* linear search. PGPROCs for prepared transactions are added to a
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* free list by TwoPhaseShmemInit().
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*/
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if (i < MaxConnections)
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{
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/* PGPROC for normal backend, add to freeProcs list */
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procs[i].links.next = (SHM_QUEUE *) ProcGlobal->freeProcs;
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ProcGlobal->freeProcs = &procs[i];
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}
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else if (i < MaxConnections + autovacuum_max_workers + 1)
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{
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/* PGPROC for AV launcher/worker, add to autovacFreeProcs list */
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procs[i].links.next = (SHM_QUEUE *) ProcGlobal->autovacFreeProcs;
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ProcGlobal->autovacFreeProcs = &procs[i];
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}
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else if (i < MaxBackends)
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{
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/* PGPROC for bgworker, add to bgworkerFreeProcs list */
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procs[i].links.next = (SHM_QUEUE *) ProcGlobal->bgworkerFreeProcs;
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ProcGlobal->bgworkerFreeProcs = &procs[i];
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}
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/* Initialize myProcLocks[] shared memory queues. */
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for (j = 0; j < NUM_LOCK_PARTITIONS; j++)
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SHMQueueInit(&(procs[i].myProcLocks[j]));
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}
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/*
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* Save pointers to the blocks of PGPROC structures reserved for auxiliary
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* processes and prepared transactions.
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*/
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AuxiliaryProcs = &procs[MaxBackends];
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PreparedXactProcs = &procs[MaxBackends + NUM_AUXILIARY_PROCS];
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/* Create ProcStructLock spinlock, too */
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ProcStructLock = (slock_t *) ShmemAlloc(sizeof(slock_t));
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SpinLockInit(ProcStructLock);
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}
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/*
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* InitProcess -- initialize a per-process data structure for this backend
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*/
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void
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InitProcess(void)
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{
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/* use volatile pointer to prevent code rearrangement */
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volatile PROC_HDR *procglobal = ProcGlobal;
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/*
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* ProcGlobal should be set up already (if we are a backend, we inherit
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* this by fork() or EXEC_BACKEND mechanism from the postmaster).
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*/
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if (procglobal == NULL)
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elog(PANIC, "proc header uninitialized");
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if (MyProc != NULL)
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elog(ERROR, "you already exist");
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/*
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* Initialize process-local latch support. This could fail if the kernel
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* is low on resources, and if so we want to exit cleanly before acquiring
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* any shared-memory resources.
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*/
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InitializeLatchSupport();
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/*
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* Try to get a proc struct from the free list. If this fails, we must be
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* out of PGPROC structures (not to mention semaphores).
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*
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* While we are holding the ProcStructLock, also copy the current shared
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* estimate of spins_per_delay to local storage.
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*/
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SpinLockAcquire(ProcStructLock);
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set_spins_per_delay(procglobal->spins_per_delay);
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if (IsAnyAutoVacuumProcess())
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MyProc = procglobal->autovacFreeProcs;
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else if (IsBackgroundWorker)
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MyProc = procglobal->bgworkerFreeProcs;
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else
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MyProc = procglobal->freeProcs;
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if (MyProc != NULL)
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{
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if (IsAnyAutoVacuumProcess())
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procglobal->autovacFreeProcs = (PGPROC *) MyProc->links.next;
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else if (IsBackgroundWorker)
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procglobal->bgworkerFreeProcs = (PGPROC *) MyProc->links.next;
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else
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procglobal->freeProcs = (PGPROC *) MyProc->links.next;
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SpinLockRelease(ProcStructLock);
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}
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else
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{
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/*
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* If we reach here, all the PGPROCs are in use. This is one of the
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* possible places to detect "too many backends", so give the standard
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* error message. XXX do we need to give a different failure message
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* in the autovacuum case?
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*/
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SpinLockRelease(ProcStructLock);
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ereport(FATAL,
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(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
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errmsg("sorry, too many clients already")));
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}
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MyPgXact = &ProcGlobal->allPgXact[MyProc->pgprocno];
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/*
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* Now that we have a PGPROC, mark ourselves as an active postmaster
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* child; this is so that the postmaster can detect it if we exit without
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* cleaning up. (XXX autovac launcher currently doesn't participate in
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* this; it probably should.)
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*/
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if (IsUnderPostmaster && !IsAutoVacuumLauncherProcess())
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MarkPostmasterChildActive();
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/*
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* Initialize all fields of MyProc, except for those previously
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* initialized by InitProcGlobal.
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*/
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SHMQueueElemInit(&(MyProc->links));
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MyProc->waitStatus = STATUS_OK;
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MyProc->lxid = InvalidLocalTransactionId;
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MyProc->fpVXIDLock = false;
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MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
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MyPgXact->xid = InvalidTransactionId;
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MyPgXact->xmin = InvalidTransactionId;
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MyProc->pid = MyProcPid;
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/* backendId, databaseId and roleId will be filled in later */
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MyProc->backendId = InvalidBackendId;
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MyProc->databaseId = InvalidOid;
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MyProc->roleId = InvalidOid;
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MyPgXact->delayChkpt = false;
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MyPgXact->vacuumFlags = 0;
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/* NB -- autovac launcher intentionally does not set IS_AUTOVACUUM */
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if (IsAutoVacuumWorkerProcess())
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MyPgXact->vacuumFlags |= PROC_IS_AUTOVACUUM;
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MyProc->lwWaiting = false;
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MyProc->lwWaitMode = 0;
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MyProc->lwWaitLink = NULL;
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MyProc->waitLock = NULL;
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MyProc->waitProcLock = NULL;
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#ifdef USE_ASSERT_CHECKING
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{
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int i;
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/* Last process should have released all locks. */
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for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
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Assert(SHMQueueEmpty(&(MyProc->myProcLocks[i])));
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}
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#endif
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MyProc->recoveryConflictPending = false;
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/* Initialize fields for sync rep */
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MyProc->waitLSN = 0;
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MyProc->syncRepState = SYNC_REP_NOT_WAITING;
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SHMQueueElemInit(&(MyProc->syncRepLinks));
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/*
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* Acquire ownership of the PGPROC's latch, so that we can use WaitLatch.
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* Note that there's no particular need to do ResetLatch here.
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*/
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OwnLatch(&MyProc->procLatch);
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/*
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* We might be reusing a semaphore that belonged to a failed process. So
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* be careful and reinitialize its value here. (This is not strictly
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* necessary anymore, but seems like a good idea for cleanliness.)
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*/
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PGSemaphoreReset(&MyProc->sem);
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/*
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* Arrange to clean up at backend exit.
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*/
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on_shmem_exit(ProcKill, 0);
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/*
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* Now that we have a PGPROC, we could try to acquire locks, so initialize
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* local state needed for LWLocks, and the deadlock checker.
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*/
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InitLWLockAccess();
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InitDeadLockChecking();
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}
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/*
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* InitProcessPhase2 -- make MyProc visible in the shared ProcArray.
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*
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* This is separate from InitProcess because we can't acquire LWLocks until
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* we've created a PGPROC, but in the EXEC_BACKEND case ProcArrayAdd won't
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* work until after we've done CreateSharedMemoryAndSemaphores.
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*/
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void
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InitProcessPhase2(void)
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{
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Assert(MyProc != NULL);
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/*
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* Add our PGPROC to the PGPROC array in shared memory.
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*/
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ProcArrayAdd(MyProc);
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/*
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* Arrange to clean that up at backend exit.
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*/
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on_shmem_exit(RemoveProcFromArray, 0);
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}
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|
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/*
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* InitAuxiliaryProcess -- create a per-auxiliary-process data structure
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*
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* This is called by bgwriter and similar processes so that they will have a
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* MyProc value that's real enough to let them wait for LWLocks. The PGPROC
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* and sema that are assigned are one of the extra ones created during
|
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* InitProcGlobal.
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*
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* Auxiliary processes are presently not expected to wait for real (lockmgr)
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* locks, so we need not set up the deadlock checker. They are never added
|
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* to the ProcArray or the sinval messaging mechanism, either. They also
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* don't get a VXID assigned, since this is only useful when we actually
|
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* hold lockmgr locks.
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*
|
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* Startup process however uses locks but never waits for them in the
|
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* normal backend sense. Startup process also takes part in sinval messaging
|
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* as a sendOnly process, so never reads messages from sinval queue. So
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* Startup process does have a VXID and does show up in pg_locks.
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*/
|
|
void
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InitAuxiliaryProcess(void)
|
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{
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PGPROC *auxproc;
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int proctype;
|
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|
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/*
|
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* ProcGlobal should be set up already (if we are a backend, we inherit
|
|
* this by fork() or EXEC_BACKEND mechanism from the postmaster).
|
|
*/
|
|
if (ProcGlobal == NULL || AuxiliaryProcs == NULL)
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elog(PANIC, "proc header uninitialized");
|
|
|
|
if (MyProc != NULL)
|
|
elog(ERROR, "you already exist");
|
|
|
|
/*
|
|
* Initialize process-local latch support. This could fail if the kernel
|
|
* is low on resources, and if so we want to exit cleanly before acquiring
|
|
* any shared-memory resources.
|
|
*/
|
|
InitializeLatchSupport();
|
|
|
|
/*
|
|
* We use the ProcStructLock to protect assignment and releasing of
|
|
* AuxiliaryProcs entries.
|
|
*
|
|
* While we are holding the ProcStructLock, also copy the current shared
|
|
* estimate of spins_per_delay to local storage.
|
|
*/
|
|
SpinLockAcquire(ProcStructLock);
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|
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set_spins_per_delay(ProcGlobal->spins_per_delay);
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|
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/*
|
|
* Find a free auxproc ... *big* trouble if there isn't one ...
|
|
*/
|
|
for (proctype = 0; proctype < NUM_AUXILIARY_PROCS; proctype++)
|
|
{
|
|
auxproc = &AuxiliaryProcs[proctype];
|
|
if (auxproc->pid == 0)
|
|
break;
|
|
}
|
|
if (proctype >= NUM_AUXILIARY_PROCS)
|
|
{
|
|
SpinLockRelease(ProcStructLock);
|
|
elog(FATAL, "all AuxiliaryProcs are in use");
|
|
}
|
|
|
|
/* Mark auxiliary proc as in use by me */
|
|
/* use volatile pointer to prevent code rearrangement */
|
|
((volatile PGPROC *) auxproc)->pid = MyProcPid;
|
|
|
|
MyProc = auxproc;
|
|
MyPgXact = &ProcGlobal->allPgXact[auxproc->pgprocno];
|
|
|
|
SpinLockRelease(ProcStructLock);
|
|
|
|
/*
|
|
* Initialize all fields of MyProc, except for those previously
|
|
* initialized by InitProcGlobal.
|
|
*/
|
|
SHMQueueElemInit(&(MyProc->links));
|
|
MyProc->waitStatus = STATUS_OK;
|
|
MyProc->lxid = InvalidLocalTransactionId;
|
|
MyProc->fpVXIDLock = false;
|
|
MyProc->fpLocalTransactionId = InvalidLocalTransactionId;
|
|
MyPgXact->xid = InvalidTransactionId;
|
|
MyPgXact->xmin = InvalidTransactionId;
|
|
MyProc->backendId = InvalidBackendId;
|
|
MyProc->databaseId = InvalidOid;
|
|
MyProc->roleId = InvalidOid;
|
|
MyPgXact->delayChkpt = false;
|
|
MyPgXact->vacuumFlags = 0;
|
|
MyProc->lwWaiting = false;
|
|
MyProc->lwWaitMode = 0;
|
|
MyProc->lwWaitLink = NULL;
|
|
MyProc->waitLock = NULL;
|
|
MyProc->waitProcLock = NULL;
|
|
#ifdef USE_ASSERT_CHECKING
|
|
{
|
|
int i;
|
|
|
|
/* Last process should have released all locks. */
|
|
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
|
|
Assert(SHMQueueEmpty(&(MyProc->myProcLocks[i])));
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* Acquire ownership of the PGPROC's latch, so that we can use WaitLatch.
|
|
* Note that there's no particular need to do ResetLatch here.
|
|
*/
|
|
OwnLatch(&MyProc->procLatch);
|
|
|
|
/*
|
|
* We might be reusing a semaphore that belonged to a failed process. So
|
|
* be careful and reinitialize its value here. (This is not strictly
|
|
* necessary anymore, but seems like a good idea for cleanliness.)
|
|
*/
|
|
PGSemaphoreReset(&MyProc->sem);
|
|
|
|
/*
|
|
* Arrange to clean up at process exit.
|
|
*/
|
|
on_shmem_exit(AuxiliaryProcKill, Int32GetDatum(proctype));
|
|
}
|
|
|
|
/*
|
|
* Record the PID and PGPROC structures for the Startup process, for use in
|
|
* ProcSendSignal(). See comments there for further explanation.
|
|
*/
|
|
void
|
|
PublishStartupProcessInformation(void)
|
|
{
|
|
/* use volatile pointer to prevent code rearrangement */
|
|
volatile PROC_HDR *procglobal = ProcGlobal;
|
|
|
|
SpinLockAcquire(ProcStructLock);
|
|
|
|
procglobal->startupProc = MyProc;
|
|
procglobal->startupProcPid = MyProcPid;
|
|
|
|
SpinLockRelease(ProcStructLock);
|
|
}
|
|
|
|
/*
|
|
* Used from bufgr to share the value of the buffer that Startup waits on,
|
|
* or to reset the value to "not waiting" (-1). This allows processing
|
|
* of recovery conflicts for buffer pins. Set is made before backends look
|
|
* at this value, so locking not required, especially since the set is
|
|
* an atomic integer set operation.
|
|
*/
|
|
void
|
|
SetStartupBufferPinWaitBufId(int bufid)
|
|
{
|
|
/* use volatile pointer to prevent code rearrangement */
|
|
volatile PROC_HDR *procglobal = ProcGlobal;
|
|
|
|
procglobal->startupBufferPinWaitBufId = bufid;
|
|
}
|
|
|
|
/*
|
|
* Used by backends when they receive a request to check for buffer pin waits.
|
|
*/
|
|
int
|
|
GetStartupBufferPinWaitBufId(void)
|
|
{
|
|
/* use volatile pointer to prevent code rearrangement */
|
|
volatile PROC_HDR *procglobal = ProcGlobal;
|
|
|
|
return procglobal->startupBufferPinWaitBufId;
|
|
}
|
|
|
|
/*
|
|
* Check whether there are at least N free PGPROC objects.
|
|
*
|
|
* Note: this is designed on the assumption that N will generally be small.
|
|
*/
|
|
bool
|
|
HaveNFreeProcs(int n)
|
|
{
|
|
PGPROC *proc;
|
|
|
|
/* use volatile pointer to prevent code rearrangement */
|
|
volatile PROC_HDR *procglobal = ProcGlobal;
|
|
|
|
SpinLockAcquire(ProcStructLock);
|
|
|
|
proc = procglobal->freeProcs;
|
|
|
|
while (n > 0 && proc != NULL)
|
|
{
|
|
proc = (PGPROC *) proc->links.next;
|
|
n--;
|
|
}
|
|
|
|
SpinLockRelease(ProcStructLock);
|
|
|
|
return (n <= 0);
|
|
}
|
|
|
|
/*
|
|
* Check if the current process is awaiting a lock.
|
|
*/
|
|
bool
|
|
IsWaitingForLock(void)
|
|
{
|
|
if (lockAwaited == NULL)
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* Cancel any pending wait for lock, when aborting a transaction, and revert
|
|
* any strong lock count acquisition for a lock being acquired.
|
|
*
|
|
* (Normally, this would only happen if we accept a cancel/die
|
|
* interrupt while waiting; but an ereport(ERROR) before or during the lock
|
|
* wait is within the realm of possibility, too.)
|
|
*/
|
|
void
|
|
LockErrorCleanup(void)
|
|
{
|
|
LWLock *partitionLock;
|
|
DisableTimeoutParams timeouts[2];
|
|
|
|
AbortStrongLockAcquire();
|
|
|
|
/* Nothing to do if we weren't waiting for a lock */
|
|
if (lockAwaited == NULL)
|
|
return;
|
|
|
|
/*
|
|
* Turn off the deadlock and lock timeout timers, if they are still
|
|
* running (see ProcSleep). Note we must preserve the LOCK_TIMEOUT
|
|
* indicator flag, since this function is executed before
|
|
* ProcessInterrupts when responding to SIGINT; else we'd lose the
|
|
* knowledge that the SIGINT came from a lock timeout and not an external
|
|
* source.
|
|
*/
|
|
timeouts[0].id = DEADLOCK_TIMEOUT;
|
|
timeouts[0].keep_indicator = false;
|
|
timeouts[1].id = LOCK_TIMEOUT;
|
|
timeouts[1].keep_indicator = true;
|
|
disable_timeouts(timeouts, 2);
|
|
|
|
/* Unlink myself from the wait queue, if on it (might not be anymore!) */
|
|
partitionLock = LockHashPartitionLock(lockAwaited->hashcode);
|
|
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
|
|
|
|
if (MyProc->links.next != NULL)
|
|
{
|
|
/* We could not have been granted the lock yet */
|
|
RemoveFromWaitQueue(MyProc, lockAwaited->hashcode);
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* Somebody kicked us off the lock queue already. Perhaps they
|
|
* granted us the lock, or perhaps they detected a deadlock. If they
|
|
* did grant us the lock, we'd better remember it in our local lock
|
|
* table.
|
|
*/
|
|
if (MyProc->waitStatus == STATUS_OK)
|
|
GrantAwaitedLock();
|
|
}
|
|
|
|
lockAwaited = NULL;
|
|
|
|
LWLockRelease(partitionLock);
|
|
|
|
/*
|
|
* We used to do PGSemaphoreReset() here to ensure that our proc's wait
|
|
* semaphore is reset to zero. This prevented a leftover wakeup signal
|
|
* from remaining in the semaphore if someone else had granted us the lock
|
|
* we wanted before we were able to remove ourselves from the wait-list.
|
|
* However, now that ProcSleep loops until waitStatus changes, a leftover
|
|
* wakeup signal isn't harmful, and it seems not worth expending cycles to
|
|
* get rid of a signal that most likely isn't there.
|
|
*/
|
|
}
|
|
|
|
|
|
/*
|
|
* ProcReleaseLocks() -- release locks associated with current transaction
|
|
* at main transaction commit or abort
|
|
*
|
|
* At main transaction commit, we release standard locks except session locks.
|
|
* At main transaction abort, we release all locks including session locks.
|
|
*
|
|
* Advisory locks are released only if they are transaction-level;
|
|
* session-level holds remain, whether this is a commit or not.
|
|
*
|
|
* At subtransaction commit, we don't release any locks (so this func is not
|
|
* needed at all); we will defer the releasing to the parent transaction.
|
|
* At subtransaction abort, we release all locks held by the subtransaction;
|
|
* this is implemented by retail releasing of the locks under control of
|
|
* the ResourceOwner mechanism.
|
|
*/
|
|
void
|
|
ProcReleaseLocks(bool isCommit)
|
|
{
|
|
if (!MyProc)
|
|
return;
|
|
/* If waiting, get off wait queue (should only be needed after error) */
|
|
LockErrorCleanup();
|
|
/* Release standard locks, including session-level if aborting */
|
|
LockReleaseAll(DEFAULT_LOCKMETHOD, !isCommit);
|
|
/* Release transaction-level advisory locks */
|
|
LockReleaseAll(USER_LOCKMETHOD, false);
|
|
}
|
|
|
|
|
|
/*
|
|
* RemoveProcFromArray() -- Remove this process from the shared ProcArray.
|
|
*/
|
|
static void
|
|
RemoveProcFromArray(int code, Datum arg)
|
|
{
|
|
Assert(MyProc != NULL);
|
|
ProcArrayRemove(MyProc, InvalidTransactionId);
|
|
}
|
|
|
|
/*
|
|
* ProcKill() -- Destroy the per-proc data structure for
|
|
* this process. Release any of its held LW locks.
|
|
*/
|
|
static void
|
|
ProcKill(int code, Datum arg)
|
|
{
|
|
/* use volatile pointer to prevent code rearrangement */
|
|
volatile PROC_HDR *procglobal = ProcGlobal;
|
|
PGPROC *proc;
|
|
|
|
Assert(MyProc != NULL);
|
|
|
|
/* Make sure we're out of the sync rep lists */
|
|
SyncRepCleanupAtProcExit();
|
|
|
|
#ifdef USE_ASSERT_CHECKING
|
|
{
|
|
int i;
|
|
|
|
/* Last process should have released all locks. */
|
|
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
|
|
Assert(SHMQueueEmpty(&(MyProc->myProcLocks[i])));
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* Release any LW locks I am holding. There really shouldn't be any, but
|
|
* it's cheap to check again before we cut the knees off the LWLock
|
|
* facility by releasing our PGPROC ...
|
|
*/
|
|
LWLockReleaseAll();
|
|
|
|
/* Make sure active replication slots are released */
|
|
if (MyReplicationSlot != NULL)
|
|
ReplicationSlotRelease();
|
|
|
|
/*
|
|
* Clear MyProc first; then disown the process latch. This is so that
|
|
* signal handlers won't try to clear the process latch after it's no
|
|
* longer ours.
|
|
*/
|
|
proc = MyProc;
|
|
MyProc = NULL;
|
|
DisownLatch(&proc->procLatch);
|
|
|
|
SpinLockAcquire(ProcStructLock);
|
|
|
|
/* Return PGPROC structure (and semaphore) to appropriate freelist */
|
|
if (IsAnyAutoVacuumProcess())
|
|
{
|
|
proc->links.next = (SHM_QUEUE *) procglobal->autovacFreeProcs;
|
|
procglobal->autovacFreeProcs = proc;
|
|
}
|
|
else if (IsBackgroundWorker)
|
|
{
|
|
proc->links.next = (SHM_QUEUE *) procglobal->bgworkerFreeProcs;
|
|
procglobal->bgworkerFreeProcs = proc;
|
|
}
|
|
else
|
|
{
|
|
proc->links.next = (SHM_QUEUE *) procglobal->freeProcs;
|
|
procglobal->freeProcs = proc;
|
|
}
|
|
|
|
/* Update shared estimate of spins_per_delay */
|
|
procglobal->spins_per_delay = update_spins_per_delay(procglobal->spins_per_delay);
|
|
|
|
SpinLockRelease(ProcStructLock);
|
|
|
|
/*
|
|
* This process is no longer present in shared memory in any meaningful
|
|
* way, so tell the postmaster we've cleaned up acceptably well. (XXX
|
|
* autovac launcher should be included here someday)
|
|
*/
|
|
if (IsUnderPostmaster && !IsAutoVacuumLauncherProcess())
|
|
MarkPostmasterChildInactive();
|
|
|
|
/* wake autovac launcher if needed -- see comments in FreeWorkerInfo */
|
|
if (AutovacuumLauncherPid != 0)
|
|
kill(AutovacuumLauncherPid, SIGUSR2);
|
|
}
|
|
|
|
/*
|
|
* AuxiliaryProcKill() -- Cut-down version of ProcKill for auxiliary
|
|
* processes (bgwriter, etc). The PGPROC and sema are not released, only
|
|
* marked as not-in-use.
|
|
*/
|
|
static void
|
|
AuxiliaryProcKill(int code, Datum arg)
|
|
{
|
|
int proctype = DatumGetInt32(arg);
|
|
PGPROC *auxproc PG_USED_FOR_ASSERTS_ONLY;
|
|
PGPROC *proc;
|
|
|
|
Assert(proctype >= 0 && proctype < NUM_AUXILIARY_PROCS);
|
|
|
|
auxproc = &AuxiliaryProcs[proctype];
|
|
|
|
Assert(MyProc == auxproc);
|
|
|
|
/* Release any LW locks I am holding (see notes above) */
|
|
LWLockReleaseAll();
|
|
|
|
/*
|
|
* Clear MyProc first; then disown the process latch. This is so that
|
|
* signal handlers won't try to clear the process latch after it's no
|
|
* longer ours.
|
|
*/
|
|
proc = MyProc;
|
|
MyProc = NULL;
|
|
DisownLatch(&proc->procLatch);
|
|
|
|
SpinLockAcquire(ProcStructLock);
|
|
|
|
/* Mark auxiliary proc no longer in use */
|
|
proc->pid = 0;
|
|
|
|
/* Update shared estimate of spins_per_delay */
|
|
ProcGlobal->spins_per_delay = update_spins_per_delay(ProcGlobal->spins_per_delay);
|
|
|
|
SpinLockRelease(ProcStructLock);
|
|
}
|
|
|
|
|
|
/*
|
|
* ProcQueue package: routines for putting processes to sleep
|
|
* and waking them up
|
|
*/
|
|
|
|
/*
|
|
* ProcQueueAlloc -- alloc/attach to a shared memory process queue
|
|
*
|
|
* Returns: a pointer to the queue
|
|
* Side Effects: Initializes the queue if it wasn't there before
|
|
*/
|
|
#ifdef NOT_USED
|
|
PROC_QUEUE *
|
|
ProcQueueAlloc(const char *name)
|
|
{
|
|
PROC_QUEUE *queue;
|
|
bool found;
|
|
|
|
queue = (PROC_QUEUE *)
|
|
ShmemInitStruct(name, sizeof(PROC_QUEUE), &found);
|
|
|
|
if (!found)
|
|
ProcQueueInit(queue);
|
|
|
|
return queue;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* ProcQueueInit -- initialize a shared memory process queue
|
|
*/
|
|
void
|
|
ProcQueueInit(PROC_QUEUE *queue)
|
|
{
|
|
SHMQueueInit(&(queue->links));
|
|
queue->size = 0;
|
|
}
|
|
|
|
|
|
/*
|
|
* ProcSleep -- put a process to sleep on the specified lock
|
|
*
|
|
* Caller must have set MyProc->heldLocks to reflect locks already held
|
|
* on the lockable object by this process (under all XIDs).
|
|
*
|
|
* The lock table's partition lock must be held at entry, and will be held
|
|
* at exit.
|
|
*
|
|
* Result: STATUS_OK if we acquired the lock, STATUS_ERROR if not (deadlock).
|
|
*
|
|
* ASSUME: that no one will fiddle with the queue until after
|
|
* we release the partition lock.
|
|
*
|
|
* NOTES: The process queue is now a priority queue for locking.
|
|
*
|
|
* P() on the semaphore should put us to sleep. The process
|
|
* semaphore is normally zero, so when we try to acquire it, we sleep.
|
|
*/
|
|
int
|
|
ProcSleep(LOCALLOCK *locallock, LockMethod lockMethodTable)
|
|
{
|
|
LOCKMODE lockmode = locallock->tag.mode;
|
|
LOCK *lock = locallock->lock;
|
|
PROCLOCK *proclock = locallock->proclock;
|
|
uint32 hashcode = locallock->hashcode;
|
|
LWLock *partitionLock = LockHashPartitionLock(hashcode);
|
|
PROC_QUEUE *waitQueue = &(lock->waitProcs);
|
|
LOCKMASK myHeldLocks = MyProc->heldLocks;
|
|
bool early_deadlock = false;
|
|
bool allow_autovacuum_cancel = true;
|
|
int myWaitStatus;
|
|
PGPROC *proc;
|
|
int i;
|
|
|
|
/*
|
|
* Determine where to add myself in the wait queue.
|
|
*
|
|
* Normally I should go at the end of the queue. However, if I already
|
|
* hold locks that conflict with the request of any previous waiter, put
|
|
* myself in the queue just in front of the first such waiter. This is not
|
|
* a necessary step, since deadlock detection would move me to before that
|
|
* waiter anyway; but it's relatively cheap to detect such a conflict
|
|
* immediately, and avoid delaying till deadlock timeout.
|
|
*
|
|
* Special case: if I find I should go in front of some waiter, check to
|
|
* see if I conflict with already-held locks or the requests before that
|
|
* waiter. If not, then just grant myself the requested lock immediately.
|
|
* This is the same as the test for immediate grant in LockAcquire, except
|
|
* we are only considering the part of the wait queue before my insertion
|
|
* point.
|
|
*/
|
|
if (myHeldLocks != 0)
|
|
{
|
|
LOCKMASK aheadRequests = 0;
|
|
|
|
proc = (PGPROC *) waitQueue->links.next;
|
|
for (i = 0; i < waitQueue->size; i++)
|
|
{
|
|
/* Must he wait for me? */
|
|
if (lockMethodTable->conflictTab[proc->waitLockMode] & myHeldLocks)
|
|
{
|
|
/* Must I wait for him ? */
|
|
if (lockMethodTable->conflictTab[lockmode] & proc->heldLocks)
|
|
{
|
|
/*
|
|
* Yes, so we have a deadlock. Easiest way to clean up
|
|
* correctly is to call RemoveFromWaitQueue(), but we
|
|
* can't do that until we are *on* the wait queue. So, set
|
|
* a flag to check below, and break out of loop. Also,
|
|
* record deadlock info for later message.
|
|
*/
|
|
RememberSimpleDeadLock(MyProc, lockmode, lock, proc);
|
|
early_deadlock = true;
|
|
break;
|
|
}
|
|
/* I must go before this waiter. Check special case. */
|
|
if ((lockMethodTable->conflictTab[lockmode] & aheadRequests) == 0 &&
|
|
LockCheckConflicts(lockMethodTable,
|
|
lockmode,
|
|
lock,
|
|
proclock) == STATUS_OK)
|
|
{
|
|
/* Skip the wait and just grant myself the lock. */
|
|
GrantLock(lock, proclock, lockmode);
|
|
GrantAwaitedLock();
|
|
return STATUS_OK;
|
|
}
|
|
/* Break out of loop to put myself before him */
|
|
break;
|
|
}
|
|
/* Nope, so advance to next waiter */
|
|
aheadRequests |= LOCKBIT_ON(proc->waitLockMode);
|
|
proc = (PGPROC *) proc->links.next;
|
|
}
|
|
|
|
/*
|
|
* If we fall out of loop normally, proc points to waitQueue head, so
|
|
* we will insert at tail of queue as desired.
|
|
*/
|
|
}
|
|
else
|
|
{
|
|
/* I hold no locks, so I can't push in front of anyone. */
|
|
proc = (PGPROC *) &(waitQueue->links);
|
|
}
|
|
|
|
/*
|
|
* Insert self into queue, ahead of the given proc (or at tail of queue).
|
|
*/
|
|
SHMQueueInsertBefore(&(proc->links), &(MyProc->links));
|
|
waitQueue->size++;
|
|
|
|
lock->waitMask |= LOCKBIT_ON(lockmode);
|
|
|
|
/* Set up wait information in PGPROC object, too */
|
|
MyProc->waitLock = lock;
|
|
MyProc->waitProcLock = proclock;
|
|
MyProc->waitLockMode = lockmode;
|
|
|
|
MyProc->waitStatus = STATUS_WAITING;
|
|
|
|
/*
|
|
* If we detected deadlock, give up without waiting. This must agree with
|
|
* CheckDeadLock's recovery code, except that we shouldn't release the
|
|
* semaphore since we haven't tried to lock it yet.
|
|
*/
|
|
if (early_deadlock)
|
|
{
|
|
RemoveFromWaitQueue(MyProc, hashcode);
|
|
return STATUS_ERROR;
|
|
}
|
|
|
|
/* mark that we are waiting for a lock */
|
|
lockAwaited = locallock;
|
|
|
|
/*
|
|
* Release the lock table's partition lock.
|
|
*
|
|
* NOTE: this may also cause us to exit critical-section state, possibly
|
|
* allowing a cancel/die interrupt to be accepted. This is OK because we
|
|
* have recorded the fact that we are waiting for a lock, and so
|
|
* LockErrorCleanup will clean up if cancel/die happens.
|
|
*/
|
|
LWLockRelease(partitionLock);
|
|
|
|
/*
|
|
* Also, now that we will successfully clean up after an ereport, it's
|
|
* safe to check to see if there's a buffer pin deadlock against the
|
|
* Startup process. Of course, that's only necessary if we're doing Hot
|
|
* Standby and are not the Startup process ourselves.
|
|
*/
|
|
if (RecoveryInProgress() && !InRecovery)
|
|
CheckRecoveryConflictDeadlock();
|
|
|
|
/* Reset deadlock_state before enabling the timeout handler */
|
|
deadlock_state = DS_NOT_YET_CHECKED;
|
|
|
|
/*
|
|
* Set timer so we can wake up after awhile and check for a deadlock. If a
|
|
* deadlock is detected, the handler releases the process's semaphore and
|
|
* sets MyProc->waitStatus = STATUS_ERROR, allowing us to know that we
|
|
* must report failure rather than success.
|
|
*
|
|
* By delaying the check until we've waited for a bit, we can avoid
|
|
* running the rather expensive deadlock-check code in most cases.
|
|
*
|
|
* If LockTimeout is set, also enable the timeout for that. We can save a
|
|
* few cycles by enabling both timeout sources in one call.
|
|
*/
|
|
if (LockTimeout > 0)
|
|
{
|
|
EnableTimeoutParams timeouts[2];
|
|
|
|
timeouts[0].id = DEADLOCK_TIMEOUT;
|
|
timeouts[0].type = TMPARAM_AFTER;
|
|
timeouts[0].delay_ms = DeadlockTimeout;
|
|
timeouts[1].id = LOCK_TIMEOUT;
|
|
timeouts[1].type = TMPARAM_AFTER;
|
|
timeouts[1].delay_ms = LockTimeout;
|
|
enable_timeouts(timeouts, 2);
|
|
}
|
|
else
|
|
enable_timeout_after(DEADLOCK_TIMEOUT, DeadlockTimeout);
|
|
|
|
/*
|
|
* If someone wakes us between LWLockRelease and PGSemaphoreLock,
|
|
* PGSemaphoreLock will not block. The wakeup is "saved" by the semaphore
|
|
* implementation. While this is normally good, there are cases where a
|
|
* saved wakeup might be leftover from a previous operation (for example,
|
|
* we aborted ProcWaitForSignal just before someone did ProcSendSignal).
|
|
* So, loop to wait again if the waitStatus shows we haven't been granted
|
|
* nor denied the lock yet.
|
|
*
|
|
* We pass interruptOK = true, which eliminates a window in which
|
|
* cancel/die interrupts would be held off undesirably. This is a promise
|
|
* that we don't mind losing control to a cancel/die interrupt here. We
|
|
* don't, because we have no shared-state-change work to do after being
|
|
* granted the lock (the grantor did it all). We do have to worry about
|
|
* canceling the deadlock timeout and updating the locallock table, but if
|
|
* we lose control to an error, LockErrorCleanup will fix that up.
|
|
*/
|
|
do
|
|
{
|
|
PGSemaphoreLock(&MyProc->sem, true);
|
|
|
|
/*
|
|
* waitStatus could change from STATUS_WAITING to something else
|
|
* asynchronously. Read it just once per loop to prevent surprising
|
|
* behavior (such as missing log messages).
|
|
*/
|
|
myWaitStatus = MyProc->waitStatus;
|
|
|
|
/*
|
|
* If we are not deadlocked, but are waiting on an autovacuum-induced
|
|
* task, send a signal to interrupt it.
|
|
*/
|
|
if (deadlock_state == DS_BLOCKED_BY_AUTOVACUUM && allow_autovacuum_cancel)
|
|
{
|
|
PGPROC *autovac = GetBlockingAutoVacuumPgproc();
|
|
PGXACT *autovac_pgxact = &ProcGlobal->allPgXact[autovac->pgprocno];
|
|
|
|
LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
|
|
|
|
/*
|
|
* Only do it if the worker is not working to protect against Xid
|
|
* wraparound.
|
|
*/
|
|
if ((autovac_pgxact->vacuumFlags & PROC_IS_AUTOVACUUM) &&
|
|
!(autovac_pgxact->vacuumFlags & PROC_VACUUM_FOR_WRAPAROUND))
|
|
{
|
|
int pid = autovac->pid;
|
|
StringInfoData locktagbuf;
|
|
StringInfoData logbuf; /* errdetail for server log */
|
|
|
|
initStringInfo(&locktagbuf);
|
|
initStringInfo(&logbuf);
|
|
DescribeLockTag(&locktagbuf, &lock->tag);
|
|
appendStringInfo(&logbuf,
|
|
_("Process %d waits for %s on %s."),
|
|
MyProcPid,
|
|
GetLockmodeName(lock->tag.locktag_lockmethodid,
|
|
lockmode),
|
|
locktagbuf.data);
|
|
|
|
/* release lock as quickly as possible */
|
|
LWLockRelease(ProcArrayLock);
|
|
|
|
ereport(LOG,
|
|
(errmsg("sending cancel to blocking autovacuum PID %d",
|
|
pid),
|
|
errdetail_log("%s", logbuf.data)));
|
|
|
|
pfree(logbuf.data);
|
|
pfree(locktagbuf.data);
|
|
|
|
/* send the autovacuum worker Back to Old Kent Road */
|
|
if (kill(pid, SIGINT) < 0)
|
|
{
|
|
/* Just a warning to allow multiple callers */
|
|
ereport(WARNING,
|
|
(errmsg("could not send signal to process %d: %m",
|
|
pid)));
|
|
}
|
|
}
|
|
else
|
|
LWLockRelease(ProcArrayLock);
|
|
|
|
/* prevent signal from being resent more than once */
|
|
allow_autovacuum_cancel = false;
|
|
}
|
|
|
|
/*
|
|
* If awoken after the deadlock check interrupt has run, and
|
|
* log_lock_waits is on, then report about the wait.
|
|
*/
|
|
if (log_lock_waits && deadlock_state != DS_NOT_YET_CHECKED)
|
|
{
|
|
StringInfoData buf,
|
|
lock_waiters_sbuf,
|
|
lock_holders_sbuf;
|
|
const char *modename;
|
|
long secs;
|
|
int usecs;
|
|
long msecs;
|
|
SHM_QUEUE *procLocks;
|
|
PROCLOCK *proclock;
|
|
bool first_holder = true,
|
|
first_waiter = true;
|
|
int lockHoldersNum = 0;
|
|
|
|
initStringInfo(&buf);
|
|
initStringInfo(&lock_waiters_sbuf);
|
|
initStringInfo(&lock_holders_sbuf);
|
|
|
|
DescribeLockTag(&buf, &locallock->tag.lock);
|
|
modename = GetLockmodeName(locallock->tag.lock.locktag_lockmethodid,
|
|
lockmode);
|
|
TimestampDifference(get_timeout_start_time(DEADLOCK_TIMEOUT),
|
|
GetCurrentTimestamp(),
|
|
&secs, &usecs);
|
|
msecs = secs * 1000 + usecs / 1000;
|
|
usecs = usecs % 1000;
|
|
|
|
/*
|
|
* we loop over the lock's procLocks to gather a list of all
|
|
* holders and waiters. Thus we will be able to provide more
|
|
* detailed information for lock debugging purposes.
|
|
*
|
|
* lock->procLocks contains all processes which hold or wait for
|
|
* this lock.
|
|
*/
|
|
|
|
LWLockAcquire(partitionLock, LW_SHARED);
|
|
|
|
procLocks = &(lock->procLocks);
|
|
proclock = (PROCLOCK *) SHMQueueNext(procLocks, procLocks,
|
|
offsetof(PROCLOCK, lockLink));
|
|
|
|
while (proclock)
|
|
{
|
|
/*
|
|
* we are a waiter if myProc->waitProcLock == proclock; we are
|
|
* a holder if it is NULL or something different
|
|
*/
|
|
if (proclock->tag.myProc->waitProcLock == proclock)
|
|
{
|
|
if (first_waiter)
|
|
{
|
|
appendStringInfo(&lock_waiters_sbuf, "%d",
|
|
proclock->tag.myProc->pid);
|
|
first_waiter = false;
|
|
}
|
|
else
|
|
appendStringInfo(&lock_waiters_sbuf, ", %d",
|
|
proclock->tag.myProc->pid);
|
|
}
|
|
else
|
|
{
|
|
if (first_holder)
|
|
{
|
|
appendStringInfo(&lock_holders_sbuf, "%d",
|
|
proclock->tag.myProc->pid);
|
|
first_holder = false;
|
|
}
|
|
else
|
|
appendStringInfo(&lock_holders_sbuf, ", %d",
|
|
proclock->tag.myProc->pid);
|
|
|
|
lockHoldersNum++;
|
|
}
|
|
|
|
proclock = (PROCLOCK *) SHMQueueNext(procLocks, &proclock->lockLink,
|
|
offsetof(PROCLOCK, lockLink));
|
|
}
|
|
|
|
LWLockRelease(partitionLock);
|
|
|
|
if (deadlock_state == DS_SOFT_DEADLOCK)
|
|
ereport(LOG,
|
|
(errmsg("process %d avoided deadlock for %s on %s by rearranging queue order after %ld.%03d ms",
|
|
MyProcPid, modename, buf.data, msecs, usecs),
|
|
(errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
|
|
"Processes holding the lock: %s. Wait queue: %s.",
|
|
lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
|
|
else if (deadlock_state == DS_HARD_DEADLOCK)
|
|
{
|
|
/*
|
|
* This message is a bit redundant with the error that will be
|
|
* reported subsequently, but in some cases the error report
|
|
* might not make it to the log (eg, if it's caught by an
|
|
* exception handler), and we want to ensure all long-wait
|
|
* events get logged.
|
|
*/
|
|
ereport(LOG,
|
|
(errmsg("process %d detected deadlock while waiting for %s on %s after %ld.%03d ms",
|
|
MyProcPid, modename, buf.data, msecs, usecs),
|
|
(errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
|
|
"Processes holding the lock: %s. Wait queue: %s.",
|
|
lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
|
|
}
|
|
|
|
if (myWaitStatus == STATUS_WAITING)
|
|
ereport(LOG,
|
|
(errmsg("process %d still waiting for %s on %s after %ld.%03d ms",
|
|
MyProcPid, modename, buf.data, msecs, usecs),
|
|
(errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
|
|
"Processes holding the lock: %s. Wait queue: %s.",
|
|
lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
|
|
else if (myWaitStatus == STATUS_OK)
|
|
ereport(LOG,
|
|
(errmsg("process %d acquired %s on %s after %ld.%03d ms",
|
|
MyProcPid, modename, buf.data, msecs, usecs)));
|
|
else
|
|
{
|
|
Assert(myWaitStatus == STATUS_ERROR);
|
|
|
|
/*
|
|
* Currently, the deadlock checker always kicks its own
|
|
* process, which means that we'll only see STATUS_ERROR when
|
|
* deadlock_state == DS_HARD_DEADLOCK, and there's no need to
|
|
* print redundant messages. But for completeness and
|
|
* future-proofing, print a message if it looks like someone
|
|
* else kicked us off the lock.
|
|
*/
|
|
if (deadlock_state != DS_HARD_DEADLOCK)
|
|
ereport(LOG,
|
|
(errmsg("process %d failed to acquire %s on %s after %ld.%03d ms",
|
|
MyProcPid, modename, buf.data, msecs, usecs),
|
|
(errdetail_log_plural("Process holding the lock: %s. Wait queue: %s.",
|
|
"Processes holding the lock: %s. Wait queue: %s.",
|
|
lockHoldersNum, lock_holders_sbuf.data, lock_waiters_sbuf.data))));
|
|
}
|
|
|
|
/*
|
|
* At this point we might still need to wait for the lock. Reset
|
|
* state so we don't print the above messages again.
|
|
*/
|
|
deadlock_state = DS_NO_DEADLOCK;
|
|
|
|
pfree(buf.data);
|
|
pfree(lock_holders_sbuf.data);
|
|
pfree(lock_waiters_sbuf.data);
|
|
}
|
|
} while (myWaitStatus == STATUS_WAITING);
|
|
|
|
/*
|
|
* Disable the timers, if they are still running. As in LockErrorCleanup,
|
|
* we must preserve the LOCK_TIMEOUT indicator flag: if a lock timeout has
|
|
* already caused QueryCancelPending to become set, we want the cancel to
|
|
* be reported as a lock timeout, not a user cancel.
|
|
*/
|
|
if (LockTimeout > 0)
|
|
{
|
|
DisableTimeoutParams timeouts[2];
|
|
|
|
timeouts[0].id = DEADLOCK_TIMEOUT;
|
|
timeouts[0].keep_indicator = false;
|
|
timeouts[1].id = LOCK_TIMEOUT;
|
|
timeouts[1].keep_indicator = true;
|
|
disable_timeouts(timeouts, 2);
|
|
}
|
|
else
|
|
disable_timeout(DEADLOCK_TIMEOUT, false);
|
|
|
|
/*
|
|
* Re-acquire the lock table's partition lock. We have to do this to hold
|
|
* off cancel/die interrupts before we can mess with lockAwaited (else we
|
|
* might have a missed or duplicated locallock update).
|
|
*/
|
|
LWLockAcquire(partitionLock, LW_EXCLUSIVE);
|
|
|
|
/*
|
|
* We no longer want LockErrorCleanup to do anything.
|
|
*/
|
|
lockAwaited = NULL;
|
|
|
|
/*
|
|
* If we got the lock, be sure to remember it in the locallock table.
|
|
*/
|
|
if (MyProc->waitStatus == STATUS_OK)
|
|
GrantAwaitedLock();
|
|
|
|
/*
|
|
* We don't have to do anything else, because the awaker did all the
|
|
* necessary update of the lock table and MyProc.
|
|
*/
|
|
return MyProc->waitStatus;
|
|
}
|
|
|
|
|
|
/*
|
|
* ProcWakeup -- wake up a process by releasing its private semaphore.
|
|
*
|
|
* Also remove the process from the wait queue and set its links invalid.
|
|
* RETURN: the next process in the wait queue.
|
|
*
|
|
* The appropriate lock partition lock must be held by caller.
|
|
*
|
|
* XXX: presently, this code is only used for the "success" case, and only
|
|
* works correctly for that case. To clean up in failure case, would need
|
|
* to twiddle the lock's request counts too --- see RemoveFromWaitQueue.
|
|
* Hence, in practice the waitStatus parameter must be STATUS_OK.
|
|
*/
|
|
PGPROC *
|
|
ProcWakeup(PGPROC *proc, int waitStatus)
|
|
{
|
|
PGPROC *retProc;
|
|
|
|
/* Proc should be sleeping ... */
|
|
if (proc->links.prev == NULL ||
|
|
proc->links.next == NULL)
|
|
return NULL;
|
|
Assert(proc->waitStatus == STATUS_WAITING);
|
|
|
|
/* Save next process before we zap the list link */
|
|
retProc = (PGPROC *) proc->links.next;
|
|
|
|
/* Remove process from wait queue */
|
|
SHMQueueDelete(&(proc->links));
|
|
(proc->waitLock->waitProcs.size)--;
|
|
|
|
/* Clean up process' state and pass it the ok/fail signal */
|
|
proc->waitLock = NULL;
|
|
proc->waitProcLock = NULL;
|
|
proc->waitStatus = waitStatus;
|
|
|
|
/* And awaken it */
|
|
PGSemaphoreUnlock(&proc->sem);
|
|
|
|
return retProc;
|
|
}
|
|
|
|
/*
|
|
* ProcLockWakeup -- routine for waking up processes when a lock is
|
|
* released (or a prior waiter is aborted). Scan all waiters
|
|
* for lock, waken any that are no longer blocked.
|
|
*
|
|
* The appropriate lock partition lock must be held by caller.
|
|
*/
|
|
void
|
|
ProcLockWakeup(LockMethod lockMethodTable, LOCK *lock)
|
|
{
|
|
PROC_QUEUE *waitQueue = &(lock->waitProcs);
|
|
int queue_size = waitQueue->size;
|
|
PGPROC *proc;
|
|
LOCKMASK aheadRequests = 0;
|
|
|
|
Assert(queue_size >= 0);
|
|
|
|
if (queue_size == 0)
|
|
return;
|
|
|
|
proc = (PGPROC *) waitQueue->links.next;
|
|
|
|
while (queue_size-- > 0)
|
|
{
|
|
LOCKMODE lockmode = proc->waitLockMode;
|
|
|
|
/*
|
|
* Waken if (a) doesn't conflict with requests of earlier waiters, and
|
|
* (b) doesn't conflict with already-held locks.
|
|
*/
|
|
if ((lockMethodTable->conflictTab[lockmode] & aheadRequests) == 0 &&
|
|
LockCheckConflicts(lockMethodTable,
|
|
lockmode,
|
|
lock,
|
|
proc->waitProcLock) == STATUS_OK)
|
|
{
|
|
/* OK to waken */
|
|
GrantLock(lock, proc->waitProcLock, lockmode);
|
|
proc = ProcWakeup(proc, STATUS_OK);
|
|
|
|
/*
|
|
* ProcWakeup removes proc from the lock's waiting process queue
|
|
* and returns the next proc in chain; don't use proc's next-link,
|
|
* because it's been cleared.
|
|
*/
|
|
}
|
|
else
|
|
{
|
|
/*
|
|
* Cannot wake this guy. Remember his request for later checks.
|
|
*/
|
|
aheadRequests |= LOCKBIT_ON(lockmode);
|
|
proc = (PGPROC *) proc->links.next;
|
|
}
|
|
}
|
|
|
|
Assert(waitQueue->size >= 0);
|
|
}
|
|
|
|
/*
|
|
* CheckDeadLock
|
|
*
|
|
* We only get to this routine if the DEADLOCK_TIMEOUT fired
|
|
* while waiting for a lock to be released by some other process. Look
|
|
* to see if there's a deadlock; if not, just return and continue waiting.
|
|
* (But signal ProcSleep to log a message, if log_lock_waits is true.)
|
|
* If we have a real deadlock, remove ourselves from the lock's wait queue
|
|
* and signal an error to ProcSleep.
|
|
*
|
|
* NB: this is run inside a signal handler, so be very wary about what is done
|
|
* here or in called routines.
|
|
*/
|
|
void
|
|
CheckDeadLock(void)
|
|
{
|
|
int i;
|
|
|
|
/*
|
|
* Acquire exclusive lock on the entire shared lock data structures. Must
|
|
* grab LWLocks in partition-number order to avoid LWLock deadlock.
|
|
*
|
|
* Note that the deadlock check interrupt had better not be enabled
|
|
* anywhere that this process itself holds lock partition locks, else this
|
|
* will wait forever. Also note that LWLockAcquire creates a critical
|
|
* section, so that this routine cannot be interrupted by cancel/die
|
|
* interrupts.
|
|
*/
|
|
for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
|
|
LWLockAcquire(LockHashPartitionLockByIndex(i), LW_EXCLUSIVE);
|
|
|
|
/*
|
|
* Check to see if we've been awoken by anyone in the interim.
|
|
*
|
|
* If we have, we can return and resume our transaction -- happy day.
|
|
* Before we are awoken the process releasing the lock grants it to us so
|
|
* we know that we don't have to wait anymore.
|
|
*
|
|
* We check by looking to see if we've been unlinked from the wait queue.
|
|
* This is quicker than checking our semaphore's state, since no kernel
|
|
* call is needed, and it is safe because we hold the lock partition lock.
|
|
*/
|
|
if (MyProc->links.prev == NULL ||
|
|
MyProc->links.next == NULL)
|
|
goto check_done;
|
|
|
|
#ifdef LOCK_DEBUG
|
|
if (Debug_deadlocks)
|
|
DumpAllLocks();
|
|
#endif
|
|
|
|
/* Run the deadlock check, and set deadlock_state for use by ProcSleep */
|
|
deadlock_state = DeadLockCheck(MyProc);
|
|
|
|
if (deadlock_state == DS_HARD_DEADLOCK)
|
|
{
|
|
/*
|
|
* Oops. We have a deadlock.
|
|
*
|
|
* Get this process out of wait state. (Note: we could do this more
|
|
* efficiently by relying on lockAwaited, but use this coding to
|
|
* preserve the flexibility to kill some other transaction than the
|
|
* one detecting the deadlock.)
|
|
*
|
|
* RemoveFromWaitQueue sets MyProc->waitStatus to STATUS_ERROR, so
|
|
* ProcSleep will report an error after we return from the signal
|
|
* handler.
|
|
*/
|
|
Assert(MyProc->waitLock != NULL);
|
|
RemoveFromWaitQueue(MyProc, LockTagHashCode(&(MyProc->waitLock->tag)));
|
|
|
|
/*
|
|
* Unlock my semaphore so that the interrupted ProcSleep() call can
|
|
* finish.
|
|
*/
|
|
PGSemaphoreUnlock(&MyProc->sem);
|
|
|
|
/*
|
|
* We're done here. Transaction abort caused by the error that
|
|
* ProcSleep will raise will cause any other locks we hold to be
|
|
* released, thus allowing other processes to wake up; we don't need
|
|
* to do that here. NOTE: an exception is that releasing locks we
|
|
* hold doesn't consider the possibility of waiters that were blocked
|
|
* behind us on the lock we just failed to get, and might now be
|
|
* wakable because we're not in front of them anymore. However,
|
|
* RemoveFromWaitQueue took care of waking up any such processes.
|
|
*/
|
|
}
|
|
else if (log_lock_waits || deadlock_state == DS_BLOCKED_BY_AUTOVACUUM)
|
|
{
|
|
/*
|
|
* Unlock my semaphore so that the interrupted ProcSleep() call can
|
|
* print the log message (we daren't do it here because we are inside
|
|
* a signal handler). It will then sleep again until someone releases
|
|
* the lock.
|
|
*
|
|
* If blocked by autovacuum, this wakeup will enable ProcSleep to send
|
|
* the canceling signal to the autovacuum worker.
|
|
*/
|
|
PGSemaphoreUnlock(&MyProc->sem);
|
|
}
|
|
|
|
/*
|
|
* And release locks. We do this in reverse order for two reasons: (1)
|
|
* Anyone else who needs more than one of the locks will be trying to lock
|
|
* them in increasing order; we don't want to release the other process
|
|
* until it can get all the locks it needs. (2) This avoids O(N^2)
|
|
* behavior inside LWLockRelease.
|
|
*/
|
|
check_done:
|
|
for (i = NUM_LOCK_PARTITIONS; --i >= 0;)
|
|
LWLockRelease(LockHashPartitionLockByIndex(i));
|
|
}
|
|
|
|
|
|
/*
|
|
* ProcWaitForSignal - wait for a signal from another backend.
|
|
*
|
|
* This can share the semaphore normally used for waiting for locks,
|
|
* since a backend could never be waiting for a lock and a signal at
|
|
* the same time. As with locks, it's OK if the signal arrives just
|
|
* before we actually reach the waiting state. Also as with locks,
|
|
* it's necessary that the caller be robust against bogus wakeups:
|
|
* always check that the desired state has occurred, and wait again
|
|
* if not. This copes with possible "leftover" wakeups.
|
|
*/
|
|
void
|
|
ProcWaitForSignal(void)
|
|
{
|
|
PGSemaphoreLock(&MyProc->sem, true);
|
|
}
|
|
|
|
/*
|
|
* ProcSendSignal - send a signal to a backend identified by PID
|
|
*/
|
|
void
|
|
ProcSendSignal(int pid)
|
|
{
|
|
PGPROC *proc = NULL;
|
|
|
|
if (RecoveryInProgress())
|
|
{
|
|
/* use volatile pointer to prevent code rearrangement */
|
|
volatile PROC_HDR *procglobal = ProcGlobal;
|
|
|
|
SpinLockAcquire(ProcStructLock);
|
|
|
|
/*
|
|
* Check to see whether it is the Startup process we wish to signal.
|
|
* This call is made by the buffer manager when it wishes to wake up a
|
|
* process that has been waiting for a pin in so it can obtain a
|
|
* cleanup lock using LockBufferForCleanup(). Startup is not a normal
|
|
* backend, so BackendPidGetProc() will not return any pid at all. So
|
|
* we remember the information for this special case.
|
|
*/
|
|
if (pid == procglobal->startupProcPid)
|
|
proc = procglobal->startupProc;
|
|
|
|
SpinLockRelease(ProcStructLock);
|
|
}
|
|
|
|
if (proc == NULL)
|
|
proc = BackendPidGetProc(pid);
|
|
|
|
if (proc != NULL)
|
|
PGSemaphoreUnlock(&proc->sem);
|
|
}
|