Quelle  test_dsm_registry.c

/*--------------------------------------------------------------------------
 *
 * test_dsm_registry.c
 *   Test the dynamic shared memory registry.
 *
 * Copyright (c) 2024-2025, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *  src/test/modules/test_dsm_registry/test_dsm_registry.c
 *
 * -------------------------------------------------------------------------
 */
#include "postgres.h"

#include "fmgr.h"
#include "storage/dsm_registry.h"
#include "storage/lwlock.h"

PG_MODULE_MAGIC;

typedef struct TestDSMRegistryStruct
{
 int   val;
 LWLock  lck;
} TestDSMRegistryStruct;

static TestDSMRegistryStruct *tdr_state;

static void
tdr_init_shmem(void *ptr)
{
 TestDSMRegistryStruct *state = (TestDSMRegistryStruct *) ptr;

 LWLockInitialize(&state->lck, LWLockNewTrancheId());
 state->val = 0;
}

static void
tdr_attach_shmem(void)
{
 bool  found;

 tdr_state = GetNamedDSMSegment("test_dsm_registry",
           sizeof(TestDSMRegistryStruct),
           tdr_init_shmem,
           &found);
 LWLockRegisterTranche(tdr_state->lck.tranche, "test_dsm_registry");
}

PG_FUNCTION_INFO_V1(set_val_in_shmem);
Datum
set_val_in_shmem(PG_FUNCTION_ARGS)
{
 tdr_attach_shmem();

 LWLockAcquire(&tdr_state->lck, LW_EXCLUSIVE);
 tdr_state->val = PG_GETARG_INT32(0);
 LWLockRelease(&tdr_state->lck);

 PG_RETURN_VOID();
}

PG_FUNCTION_INFO_V1(get_val_in_shmem);
Datum
get_val_in_shmem(PG_FUNCTION_ARGS)
{
 int   ret;

 tdr_attach_shmem();

 LWLockAcquire(&tdr_state->lck, LW_SHARED);
 ret = tdr_state->val;
 LWLockRelease(&tdr_state->lck);

 PG_RETURN_INT32(ret);
}