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-rw-r--r--src/backend/utils/activity/backend_status.c88
-rw-r--r--src/backend/utils/adt/lockfuncs.c4
-rw-r--r--src/backend/utils/init/postinit.c50
3 files changed, 94 insertions, 48 deletions
diff --git a/src/backend/utils/activity/backend_status.c b/src/backend/utils/activity/backend_status.c
index c7ed1e6d7ac..079321599d6 100644
--- a/src/backend/utils/activity/backend_status.c
+++ b/src/backend/utils/activity/backend_status.c
@@ -27,18 +27,6 @@
/* ----------
- * Total number of backends including auxiliary
- *
- * We reserve a slot for each possible BackendId, plus one for each
- * possible auxiliary process type. (This scheme assumes there is not
- * more than one of any auxiliary process type at a time.) MaxBackends
- * includes autovacuum workers and background workers as well.
- * ----------
- */
-#define NumBackendStatSlots (MaxBackends + NUM_AUXPROCTYPES)
-
-
-/* ----------
* GUC parameters
* ----------
*/
@@ -75,36 +63,52 @@ static MemoryContext backendStatusSnapContext;
static void pgstat_beshutdown_hook(int code, Datum arg);
static void pgstat_read_current_status(void);
static void pgstat_setup_backend_status_context(void);
+static inline int GetNumBackendStatSlots(void);
/*
+ * Retrieve the total number of backends including auxiliary
+ *
+ * We reserve a slot for each possible BackendId, plus one for each possible
+ * auxiliary process type. (This scheme assumes there is not more than one of
+ * any auxiliary process type at a time.) MaxBackends includes autovacuum
+ * workers and background workers as well.
+ */
+static inline int
+GetNumBackendStatSlots(void)
+{
+ return GetMaxBackends() + NUM_AUXPROCTYPES;
+}
+
+/*
* Report shared-memory space needed by CreateSharedBackendStatus.
*/
Size
BackendStatusShmemSize(void)
{
Size size;
+ int numBackendStatSlots = GetNumBackendStatSlots();
/* BackendStatusArray: */
- size = mul_size(sizeof(PgBackendStatus), NumBackendStatSlots);
+ size = mul_size(sizeof(PgBackendStatus), numBackendStatSlots);
/* BackendAppnameBuffer: */
size = add_size(size,
- mul_size(NAMEDATALEN, NumBackendStatSlots));
+ mul_size(NAMEDATALEN, numBackendStatSlots));
/* BackendClientHostnameBuffer: */
size = add_size(size,
- mul_size(NAMEDATALEN, NumBackendStatSlots));
+ mul_size(NAMEDATALEN, numBackendStatSlots));
/* BackendActivityBuffer: */
size = add_size(size,
- mul_size(pgstat_track_activity_query_size, NumBackendStatSlots));
+ mul_size(pgstat_track_activity_query_size, numBackendStatSlots));
#ifdef USE_SSL
/* BackendSslStatusBuffer: */
size = add_size(size,
- mul_size(sizeof(PgBackendSSLStatus), NumBackendStatSlots));
+ mul_size(sizeof(PgBackendSSLStatus), numBackendStatSlots));
#endif
#ifdef ENABLE_GSS
/* BackendGssStatusBuffer: */
size = add_size(size,
- mul_size(sizeof(PgBackendGSSStatus), NumBackendStatSlots));
+ mul_size(sizeof(PgBackendGSSStatus), numBackendStatSlots));
#endif
return size;
}
@@ -120,9 +124,10 @@ CreateSharedBackendStatus(void)
bool found;
int i;
char *buffer;
+ int numBackendStatSlots = GetNumBackendStatSlots();
/* Create or attach to the shared array */
- size = mul_size(sizeof(PgBackendStatus), NumBackendStatSlots);
+ size = mul_size(sizeof(PgBackendStatus), numBackendStatSlots);
BackendStatusArray = (PgBackendStatus *)
ShmemInitStruct("Backend Status Array", size, &found);
@@ -135,7 +140,7 @@ CreateSharedBackendStatus(void)
}
/* Create or attach to the shared appname buffer */
- size = mul_size(NAMEDATALEN, NumBackendStatSlots);
+ size = mul_size(NAMEDATALEN, numBackendStatSlots);
BackendAppnameBuffer = (char *)
ShmemInitStruct("Backend Application Name Buffer", size, &found);
@@ -145,7 +150,7 @@ CreateSharedBackendStatus(void)
/* Initialize st_appname pointers. */
buffer = BackendAppnameBuffer;
- for (i = 0; i < NumBackendStatSlots; i++)
+ for (i = 0; i < numBackendStatSlots; i++)
{
BackendStatusArray[i].st_appname = buffer;
buffer += NAMEDATALEN;
@@ -153,7 +158,7 @@ CreateSharedBackendStatus(void)
}
/* Create or attach to the shared client hostname buffer */
- size = mul_size(NAMEDATALEN, NumBackendStatSlots);
+ size = mul_size(NAMEDATALEN, numBackendStatSlots);
BackendClientHostnameBuffer = (char *)
ShmemInitStruct("Backend Client Host Name Buffer", size, &found);
@@ -163,7 +168,7 @@ CreateSharedBackendStatus(void)
/* Initialize st_clienthostname pointers. */
buffer = BackendClientHostnameBuffer;
- for (i = 0; i < NumBackendStatSlots; i++)
+ for (i = 0; i < numBackendStatSlots; i++)
{
BackendStatusArray[i].st_clienthostname = buffer;
buffer += NAMEDATALEN;
@@ -172,7 +177,7 @@ CreateSharedBackendStatus(void)
/* Create or attach to the shared activity buffer */
BackendActivityBufferSize = mul_size(pgstat_track_activity_query_size,
- NumBackendStatSlots);
+ numBackendStatSlots);
BackendActivityBuffer = (char *)
ShmemInitStruct("Backend Activity Buffer",
BackendActivityBufferSize,
@@ -184,7 +189,7 @@ CreateSharedBackendStatus(void)
/* Initialize st_activity pointers. */
buffer = BackendActivityBuffer;
- for (i = 0; i < NumBackendStatSlots; i++)
+ for (i = 0; i < numBackendStatSlots; i++)
{
BackendStatusArray[i].st_activity_raw = buffer;
buffer += pgstat_track_activity_query_size;
@@ -193,7 +198,7 @@ CreateSharedBackendStatus(void)
#ifdef USE_SSL
/* Create or attach to the shared SSL status buffer */
- size = mul_size(sizeof(PgBackendSSLStatus), NumBackendStatSlots);
+ size = mul_size(sizeof(PgBackendSSLStatus), numBackendStatSlots);
BackendSslStatusBuffer = (PgBackendSSLStatus *)
ShmemInitStruct("Backend SSL Status Buffer", size, &found);
@@ -205,7 +210,7 @@ CreateSharedBackendStatus(void)
/* Initialize st_sslstatus pointers. */
ptr = BackendSslStatusBuffer;
- for (i = 0; i < NumBackendStatSlots; i++)
+ for (i = 0; i < numBackendStatSlots; i++)
{
BackendStatusArray[i].st_sslstatus = ptr;
ptr++;
@@ -215,7 +220,7 @@ CreateSharedBackendStatus(void)
#ifdef ENABLE_GSS
/* Create or attach to the shared GSSAPI status buffer */
- size = mul_size(sizeof(PgBackendGSSStatus), NumBackendStatSlots);
+ size = mul_size(sizeof(PgBackendGSSStatus), numBackendStatSlots);
BackendGssStatusBuffer = (PgBackendGSSStatus *)
ShmemInitStruct("Backend GSS Status Buffer", size, &found);
@@ -227,7 +232,7 @@ CreateSharedBackendStatus(void)
/* Initialize st_gssstatus pointers. */
ptr = BackendGssStatusBuffer;
- for (i = 0; i < NumBackendStatSlots; i++)
+ for (i = 0; i < numBackendStatSlots; i++)
{
BackendStatusArray[i].st_gssstatus = ptr;
ptr++;
@@ -251,7 +256,7 @@ pgstat_beinit(void)
/* Initialize MyBEEntry */
if (MyBackendId != InvalidBackendId)
{
- Assert(MyBackendId >= 1 && MyBackendId <= MaxBackends);
+ Assert(MyBackendId >= 1 && MyBackendId <= GetMaxBackends());
MyBEEntry = &BackendStatusArray[MyBackendId - 1];
}
else
@@ -267,7 +272,7 @@ pgstat_beinit(void)
* MaxBackends + AuxBackendType + 1 as the index of the slot for an
* auxiliary process.
*/
- MyBEEntry = &BackendStatusArray[MaxBackends + MyAuxProcType];
+ MyBEEntry = &BackendStatusArray[GetMaxBackends() + MyAuxProcType];
}
/* Set up a process-exit hook to clean up */
@@ -739,6 +744,7 @@ pgstat_read_current_status(void)
PgBackendGSSStatus *localgssstatus;
#endif
int i;
+ int numBackendStatSlots = GetNumBackendStatSlots();
if (localBackendStatusTable)
return; /* already done */
@@ -755,32 +761,32 @@ pgstat_read_current_status(void)
*/
localtable = (LocalPgBackendStatus *)
MemoryContextAlloc(backendStatusSnapContext,
- sizeof(LocalPgBackendStatus) * NumBackendStatSlots);
+ sizeof(LocalPgBackendStatus) * numBackendStatSlots);
localappname = (char *)
MemoryContextAlloc(backendStatusSnapContext,
- NAMEDATALEN * NumBackendStatSlots);
+ NAMEDATALEN * numBackendStatSlots);
localclienthostname = (char *)
MemoryContextAlloc(backendStatusSnapContext,
- NAMEDATALEN * NumBackendStatSlots);
+ NAMEDATALEN * numBackendStatSlots);
localactivity = (char *)
MemoryContextAllocHuge(backendStatusSnapContext,
- pgstat_track_activity_query_size * NumBackendStatSlots);
+ pgstat_track_activity_query_size * numBackendStatSlots);
#ifdef USE_SSL
localsslstatus = (PgBackendSSLStatus *)
MemoryContextAlloc(backendStatusSnapContext,
- sizeof(PgBackendSSLStatus) * NumBackendStatSlots);
+ sizeof(PgBackendSSLStatus) * numBackendStatSlots);
#endif
#ifdef ENABLE_GSS
localgssstatus = (PgBackendGSSStatus *)
MemoryContextAlloc(backendStatusSnapContext,
- sizeof(PgBackendGSSStatus) * NumBackendStatSlots);
+ sizeof(PgBackendGSSStatus) * numBackendStatSlots);
#endif
localNumBackends = 0;
beentry = BackendStatusArray;
localentry = localtable;
- for (i = 1; i <= NumBackendStatSlots; i++)
+ for (i = 1; i <= numBackendStatSlots; i++)
{
/*
* Follow the protocol of retrying if st_changecount changes while we
@@ -893,9 +899,10 @@ pgstat_get_backend_current_activity(int pid, bool checkUser)
{
PgBackendStatus *beentry;
int i;
+ int max_backends = GetMaxBackends();
beentry = BackendStatusArray;
- for (i = 1; i <= MaxBackends; i++)
+ for (i = 1; i <= max_backends; i++)
{
/*
* Although we expect the target backend's entry to be stable, that
@@ -971,6 +978,7 @@ pgstat_get_crashed_backend_activity(int pid, char *buffer, int buflen)
{
volatile PgBackendStatus *beentry;
int i;
+ int max_backends = GetMaxBackends();
beentry = BackendStatusArray;
@@ -981,7 +989,7 @@ pgstat_get_crashed_backend_activity(int pid, char *buffer, int buflen)
if (beentry == NULL || BackendActivityBuffer == NULL)
return NULL;
- for (i = 1; i <= MaxBackends; i++)
+ for (i = 1; i <= max_backends; i++)
{
if (beentry->st_procpid == pid)
{
diff --git a/src/backend/utils/adt/lockfuncs.c b/src/backend/utils/adt/lockfuncs.c
index 023a004ac89..4e517b28e17 100644
--- a/src/backend/utils/adt/lockfuncs.c
+++ b/src/backend/utils/adt/lockfuncs.c
@@ -561,11 +561,11 @@ pg_safe_snapshot_blocking_pids(PG_FUNCTION_ARGS)
Datum *blocker_datums;
/* A buffer big enough for any possible blocker list without truncation */
- blockers = (int *) palloc(MaxBackends * sizeof(int));
+ blockers = (int *) palloc(GetMaxBackends() * sizeof(int));
/* Collect a snapshot of processes waited for by GetSafeSnapshot */
num_blockers =
- GetSafeSnapshotBlockingPids(blocked_pid, blockers, MaxBackends);
+ GetSafeSnapshotBlockingPids(blocked_pid, blockers, GetMaxBackends());
/* Convert int array to Datum array */
if (num_blockers > 0)
diff --git a/src/backend/utils/init/postinit.c b/src/backend/utils/init/postinit.c
index 5b9ed2f6f52..ca53912f151 100644
--- a/src/backend/utils/init/postinit.c
+++ b/src/backend/utils/init/postinit.c
@@ -25,6 +25,7 @@
#include "access/session.h"
#include "access/sysattr.h"
#include "access/tableam.h"
+#include "access/twophase.h"
#include "access/xact.h"
#include "access/xlog.h"
#include "access/xloginsert.h"
@@ -65,6 +66,9 @@
#include "utils/syscache.h"
#include "utils/timeout.h"
+static int MaxBackends = 0;
+static int MaxBackendsInitialized = false;
+
static HeapTuple GetDatabaseTuple(const char *dbname);
static HeapTuple GetDatabaseTupleByOid(Oid dboid);
static void PerformAuthentication(Port *port);
@@ -495,15 +499,49 @@ pg_split_opts(char **argv, int *argcp, const char *optstr)
void
InitializeMaxBackends(void)
{
- Assert(MaxBackends == 0);
-
/* the extra unit accounts for the autovacuum launcher */
- MaxBackends = MaxConnections + autovacuum_max_workers + 1 +
- max_worker_processes + max_wal_senders;
+ SetMaxBackends(MaxConnections + autovacuum_max_workers + 1 +
+ max_worker_processes + max_wal_senders);
+}
+
+/*
+ * Safely retrieve the value of MaxBackends.
+ *
+ * Previously, MaxBackends was externally visible, but it was often used before
+ * it was initialized (e.g., in preloaded libraries' _PG_init() functions).
+ * Unfortunately, we cannot initialize MaxBackends before processing
+ * shared_preload_libraries because the libraries sometimes alter GUCs that are
+ * used to calculate its value. Instead, we provide this function for accessing
+ * MaxBackends, and we ERROR if someone calls it before it is initialized.
+ */
+int
+GetMaxBackends(void)
+{
+ if (unlikely(!MaxBackendsInitialized))
+ elog(ERROR, "MaxBackends not yet initialized");
+
+ return MaxBackends;
+}
+
+/*
+ * Set the value of MaxBackends.
+ *
+ * This should only be used by InitializeMaxBackends() and
+ * restore_backend_variables(). If MaxBackends is already initialized or the
+ * specified value is greater than the maximum, this will ERROR.
+ */
+void
+SetMaxBackends(int max_backends)
+{
+ if (MaxBackendsInitialized)
+ elog(ERROR, "MaxBackends already initialized");
/* internal error because the values were all checked previously */
- if (MaxBackends > MAX_BACKENDS)
+ if (max_backends > MAX_BACKENDS)
elog(ERROR, "too many backends configured");
+
+ MaxBackends = max_backends;
+ MaxBackendsInitialized = true;
}
/*
@@ -609,7 +647,7 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
SharedInvalBackendInit(false);
- if (MyBackendId > MaxBackends || MyBackendId <= 0)
+ if (MyBackendId > GetMaxBackends() || MyBackendId <= 0)
elog(FATAL, "bad backend ID: %d", MyBackendId);
/* Now that we have a BackendId, we can participate in ProcSignal */
generated by cgit v1.2.3 (git 2.25.1) at 2025-05-31 20:06:54 +0000