test_dsm_registry.c

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/*--------------------------------------------------------------------------
 *
 * 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_UINT32(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_UINT32(ret);
}