Function SharedFileSetOnDetach

src/backend/storage/file/sharedfileset.c:240–259

* Callback function that will be invoked when this backend detaches from a * DSM segment holding a SharedFileSet that it has created or attached to. If * we are the last to detach, then try to remove the directories and * everything in them. We can't raise an error on failures, because this runs * in error cleanup paths. */

 * in error cleanup paths.
 */
static void
SharedFileSetOnDetach(dsm_segment *segment, Datum datum)
{
	bool		unlink_all = false;
	SharedFileSet *fileset = (SharedFileSet *) DatumGetPointer(datum);

	SpinLockAcquire(&fileset->mutex);
	Assert(fileset->refcnt > 0);
	if (--fileset->refcnt == 0)
		unlink_all = true;
	SpinLockRelease(&fileset->mutex);

	/*
	 * If we are the last to detach, we delete the directory in all
	 * tablespaces.  Note that we are still actually attached for the rest of
	 * this function so we can safely access its data.
	 */
	if (unlink_all)
		SharedFileSetDeleteAll(fileset);
}

/*
 * Callback function that will be invoked on the process exit.  This will