static void
test_atomic_flag(void)
{
pg_atomic_flag flag;
pg_atomic_init_flag(&flag);
if (!pg_atomic_unlocked_test_flag(&flag))
elog(ERROR, "flag: unexpectedly set");
if (!pg_atomic_test_set_flag(&flag))
elog(ERROR, "flag: couldn't set");
if (pg_atomic_unlocked_test_flag(&flag))
elog(ERROR, "flag: unexpectedly unset");
if (pg_atomic_test_set_flag(&flag))
elog(ERROR, "flag: set spuriously #2");
pg_atomic_clear_flag(&flag);
if (!pg_atomic_unlocked_test_flag(&flag))
elog(ERROR, "flag: unexpectedly set #2");
if (!pg_atomic_test_set_flag(&flag))
elog(ERROR, "flag: couldn't set");
pg_atomic_clear_flag(&flag);
}
void cfs_lock_file(FileMap* map, char const* file_path)
{
long delay = CFS_LOCK_MIN_TIMEOUT;
while (true) {
uint64 count = pg_atomic_fetch_add_u32(&map->lock, 1);
if (count < CFS_GC_LOCK) {
break;
}
if (InRecovery) {
/* Uhhh... looks like last GC was interrupted.
* Try to recover file
*/
char* map_bck_path = psprintf("%s.map.bck", file_path);
char* file_bck_path = psprintf("%s.bck", file_path);
if (access(file_bck_path, R_OK) != 0) {
/* There is no backup file: new map should be constructed */
int md2 = open(map_bck_path, O_RDWR|PG_BINARY, 0);
if (md2 >= 0) {
/* Recover map */
if (!cfs_read_file(md2, map, sizeof(FileMap))) {
elog(LOG, "Failed to read file %s: %m", map_bck_path);
}
close(md2);
}
} else {
/* Presence of backup file means that we still have unchanged data and map files.
* Just remove backup files, grab lock and continue processing
*/
unlink(file_bck_path);
unlink(map_bck_path);
}
pfree(file_bck_path);
pfree(map_bck_path);
break;
}
pg_atomic_fetch_sub_u32(&map->lock, 1);
pg_usleep(delay);
if (delay < CFS_LOCK_MAX_TIMEOUT) {
delay *= 2;
}
}
if (IsUnderPostmaster && cfs_gc_workers != 0 && pg_atomic_test_set_flag(&cfs_state->gc_started))
{
cfs_start_background_gc();
}
}
Datum cfs_start_gc(PG_FUNCTION_ARGS)
{
int i = 0;
if (cfs_gc_workers == 0 && pg_atomic_test_set_flag(&cfs_state->gc_started))
{
int j;
BackgroundWorkerHandle** handles;
cfs_stop = true; /* do just one iteration */
cfs_state->max_iterations = 1;
cfs_state->n_workers = PG_GETARG_INT32(0);
handles = (BackgroundWorkerHandle**)palloc(cfs_state->n_workers*sizeof(BackgroundWorkerHandle*));
for (i = 0; i < cfs_state->n_workers; i++) {
BackgroundWorker worker;
MemSet(&worker, 0, sizeof(worker));
sprintf(worker.bgw_name, "cfs-worker-%d", i);
worker.bgw_flags = BGWORKER_SHMEM_ACCESS;
worker.bgw_start_time = BgWorkerStart_ConsistentState;
worker.bgw_restart_time = 1;
worker.bgw_main = cfs_bgworker_main;
worker.bgw_main_arg = Int32GetDatum(i);
if (!RegisterDynamicBackgroundWorker(&worker, &handles[i])) {
break;
}
}
for (j = 0; j < i; j++) {
WaitForBackgroundWorkerShutdown(handles[j]);
}
pfree(handles);
pg_atomic_clear_flag(&cfs_state->gc_started);
}
PG_RETURN_INT32(i);
}