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.

Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Discussion: https://www.postgresql.org/message-id/47aaf57e-1b7b-4e12-bda2-0316081ff50e@iki.fi

diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 8c134eaca886a9455313a7bc68529048130e5adb..434e06430220e29db68642cec1e42cd763fd3bcd 100644 (file)
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -99,8 +99,6 @@ typedef struct
 #ifdef USE_INJECTION_POINTS
        struct InjectionPointsCtl *ActiveInjectionPoints;
 #endif
-       LWLockTrancheShmemData *LWLockTranches;
-       LWLockPadded *MainLWLockArray;
        PROC_HDR   *ProcGlobal;
        PGPROC     *AuxiliaryProcs;
        PGPROC     *PreparedXactProcs;
@@ -726,8 +724,6 @@ save_backend_variables(BackendParameters *param,
        param->ActiveInjectionPoints = ActiveInjectionPoints;
 #endif
 
-       param->LWLockTranches = LWLockTranches;
-       param->MainLWLockArray = MainLWLockArray;
        param->ProcGlobal = ProcGlobal;
        param->AuxiliaryProcs = AuxiliaryProcs;
        param->PreparedXactProcs = PreparedXactProcs;
@@ -982,8 +978,6 @@ restore_backend_variables(BackendParameters *param)
        ActiveInjectionPoints = param->ActiveInjectionPoints;
 #endif
 
-       LWLockTranches = param->LWLockTranches;
-       MainLWLockArray = param->MainLWLockArray;
        ProcGlobal = param->ProcGlobal;
        AuxiliaryProcs = param->AuxiliaryProcs;
        PreparedXactProcs = param->PreparedXactProcs;

diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c
index 3d3f153809b5d1f61ecff62b34d0d0558e95d2ef..d692d419846bb082731ae9edd1fa9eb885bd41d8 100644 (file)
--- a/src/backend/storage/ipc/ipci.c
+++ b/src/backend/storage/ipc/ipci.c
@@ -250,9 +250,9 @@ static void
 CreateOrAttachShmemStructs(void)
 {
        /*
-        * Now initialize LWLocks, which do shared memory allocation.
+        * Set up LWLocks.  They are needed by most other subsystems.
         */
-       CreateLWLocks();
+       LWLockShmemInit();
 
        dsm_shmem_init();
        DSMRegistryShmemInit();

diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c
index f9e368770b75c40ea8539900afae75dac3d34581..241f1f08430c10f19e84018e0c64dd96edbc84e2 100644 (file)
--- 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;
@@ -426,23 +429,32 @@ LWLockShmemSize(void)
  * and initialize it.
  */
 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 30557631eb807fceabad26df1f5617e1c9364925..61f0dbe749ae8478adf71a80f78db06bd0c7439f 100644 (file)
--- 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);