From d5362cffef3de02259841ce4b049b7bd8898bef9 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Thu, 26 Mar 2026 13:26:59 +0200 Subject: [PATCH v1 4/5] Use ShmemInitStruct to allocate lwlock.c's shared memory It's nice to have them show up in pg_shmem_allocations like all other shmem areas. ShmemInitStruct() depends on ShmemIndexLock, but only after postmaster startup. --- src/backend/postmaster/launch_backend.c | 3 -- src/backend/storage/ipc/ipci.c | 6 ++-- src/backend/storage/ipc/shmem.c | 15 ++++++---- src/backend/storage/lmgr/lwlock.c | 39 ++++++++++++++++--------- src/include/storage/lwlock.h | 7 +---- 5 files changed, 39 insertions(+), 31 deletions(-) diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c index 8c134eaca88..8aaf427df48 100644 --- a/src/backend/postmaster/launch_backend.c +++ b/src/backend/postmaster/launch_backend.c @@ -99,7 +99,6 @@ typedef struct #ifdef USE_INJECTION_POINTS struct InjectionPointsCtl *ActiveInjectionPoints; #endif - LWLockTrancheShmemData *LWLockTranches; LWLockPadded *MainLWLockArray; PROC_HDR *ProcGlobal; PGPROC *AuxiliaryProcs; @@ -726,7 +725,6 @@ save_backend_variables(BackendParameters *param, param->ActiveInjectionPoints = ActiveInjectionPoints; #endif - param->LWLockTranches = LWLockTranches; param->MainLWLockArray = MainLWLockArray; param->ProcGlobal = ProcGlobal; param->AuxiliaryProcs = AuxiliaryProcs; @@ -982,7 +980,6 @@ restore_backend_variables(BackendParameters *param) ActiveInjectionPoints = param->ActiveInjectionPoints; #endif - LWLockTranches = param->LWLockTranches; MainLWLockArray = param->MainLWLockArray; ProcGlobal = param->ProcGlobal; AuxiliaryProcs = param->AuxiliaryProcs; diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c index 3d3f153809b..036db3fa514 100644 --- a/src/backend/storage/ipc/ipci.c +++ b/src/backend/storage/ipc/ipci.c @@ -249,10 +249,8 @@ CreateSharedMemoryAndSemaphores(void) static void CreateOrAttachShmemStructs(void) { - /* - * Now initialize LWLocks, which do shared memory allocation. - */ - CreateLWLocks(); + /* Start with initializing LWLock tranches */ + LWLockShmemInit(); dsm_shmem_init(); DSMRegistryShmemInit(); diff --git a/src/backend/storage/ipc/shmem.c b/src/backend/storage/ipc/shmem.c index f392faa534f..339fbba3404 100644 --- a/src/backend/storage/ipc/shmem.c +++ b/src/backend/storage/ipc/shmem.c @@ -379,7 +379,8 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr) Assert(ShmemIndex != NULL); - LWLockAcquire(ShmemIndexLock, LW_EXCLUSIVE); + if (IsUnderPostmaster) + LWLockAcquire(ShmemIndexLock, LW_EXCLUSIVE); /* look it up in the shmem index */ result = (ShmemIndexEnt *) @@ -387,7 +388,8 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr) if (!result) { - LWLockRelease(ShmemIndexLock); + if (IsUnderPostmaster) + LWLockRelease(ShmemIndexLock); ereport(ERROR, (errcode(ERRCODE_OUT_OF_MEMORY), errmsg("could not create ShmemIndex entry for data structure \"%s\"", @@ -403,7 +405,8 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr) */ if (result->size != size) { - LWLockRelease(ShmemIndexLock); + if (IsUnderPostmaster) + LWLockRelease(ShmemIndexLock); ereport(ERROR, (errmsg("ShmemIndex entry size is wrong for data structure" " \"%s\": expected %zu, actual %zu", @@ -421,7 +424,8 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr) { /* out of memory; remove the failed ShmemIndex entry */ hash_search(ShmemIndex, name, HASH_REMOVE, NULL); - LWLockRelease(ShmemIndexLock); + if (IsUnderPostmaster) + LWLockRelease(ShmemIndexLock); ereport(ERROR, (errcode(ERRCODE_OUT_OF_MEMORY), errmsg("not enough shared memory for data structure" @@ -433,7 +437,8 @@ ShmemInitStruct(const char *name, Size size, bool *foundPtr) result->location = structPtr; } - LWLockRelease(ShmemIndexLock); + if (IsUnderPostmaster) + LWLockRelease(ShmemIndexLock); Assert(ShmemAddrIsValid(structPtr)); diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c index 4c01afce2f7..7bb005a5833 100644 --- a/src/backend/storage/lmgr/lwlock.c +++ b/src/backend/storage/lmgr/lwlock.c @@ -193,9 +193,12 @@ typedef struct LWLockTrancheShmemData int num_user_defined; /* 'user_defined' entries in use */ slock_t lock; /* protects the above */ + + /* Size of MainLWLockArray */ + int num_main_array_locks; } LWLockTrancheShmemData; -LWLockTrancheShmemData *LWLockTranches; +static LWLockTrancheShmemData *LWLockTranches; /* backend-local copy of NamedLWLockTranches->num_user_defined */ static int LocalNumUserDefinedTranches; @@ -405,7 +408,8 @@ NumLWLocksForNamedTranches(void) } /* - * Compute shmem space needed for LWLocks and named tranches. + * Compute shmem space needed for user-defined tranches and the main LWLock + * array. */ Size LWLockShmemSize(void) @@ -424,27 +428,36 @@ LWLockShmemSize(void) } /* - * Allocate shmem space for the main LWLock array and all tranches and - * initialize it. + * Allocate and initialize shmem for user-defined LWLock tranches and the main + * LWLock array. */ void -CreateLWLocks(void) +LWLockShmemInit(void) { int numLocks; + bool found; - if (!IsUnderPostmaster) + LWLockTranches = (LWLockTrancheShmemData *) + ShmemInitStruct("LWLock tranches", sizeof(LWLockTrancheShmemData), &found); + if (!found) { - /* Allocate space for LWLockTranches */ - LWLockTranches = (LWLockTrancheShmemData *) - ShmemAlloc(sizeof(LWLockTrancheShmemData)); + /* Calculate total number of locks needed in the main array */ + LWLockTranches->num_main_array_locks = + NUM_FIXED_LWLOCKS + NumLWLocksForNamedTranches(); /* Initialize the dynamic-allocation counter for tranches */ - SpinLockInit(&LWLockTranches->lock); LWLockTranches->num_user_defined = 0; - /* Allocate and initialize the main array */ - numLocks = NUM_FIXED_LWLOCKS + NumLWLocksForNamedTranches(); - MainLWLockArray = (LWLockPadded *) ShmemAlloc(numLocks * sizeof(LWLockPadded)); + SpinLockInit(&LWLockTranches->lock); + } + + /* Allocate and initialize the main array */ + numLocks = LWLockTranches->num_main_array_locks; + MainLWLockArray = (LWLockPadded *) + ShmemInitStruct("Main LWLock array", numLocks * sizeof(LWLockPadded), &found); + if (!found) + { + /* Initialize all LWLocks */ InitializeLWLocks(numLocks); } } diff --git a/src/include/storage/lwlock.h b/src/include/storage/lwlock.h index 30557631eb8..61f0dbe749a 100644 --- a/src/include/storage/lwlock.h +++ b/src/include/storage/lwlock.h @@ -73,11 +73,6 @@ typedef union LWLockPadded extern PGDLLIMPORT LWLockPadded *MainLWLockArray; -/* forward declaration of private type for use only by lwlock.c */ -typedef struct LWLockTrancheShmemData LWLockTrancheShmemData; - -extern PGDLLIMPORT LWLockTrancheShmemData *LWLockTranches; - /* * It's a bit odd to declare NUM_BUFFER_PARTITIONS and NUM_LOCK_PARTITIONS * here, but we need them to figure out offsets within MainLWLockArray, and @@ -132,7 +127,7 @@ extern bool LWLockWaitForVar(LWLock *lock, pg_atomic_uint64 *valptr, uint64 oldv extern void LWLockUpdateVar(LWLock *lock, pg_atomic_uint64 *valptr, uint64 val); extern Size LWLockShmemSize(void); -extern void CreateLWLocks(void); +extern void LWLockShmemInit(void); extern void InitLWLockAccess(void); extern const char *GetLWLockIdentifier(uint32 classId, uint16 eventId); -- 2.47.3