Function packed_refs_lock

refs/packed-backend.c:1217–1274

}

int packed_refs_lock(struct ref_store *ref_store, int flags, struct strbuf *err)
{
	struct packed_ref_store *refs =
		packed_downcast(ref_store, REF_STORE_WRITE | REF_STORE_MAIN,
				"packed_refs_lock");
	static int timeout_configured = 0;
	static int timeout_value = 1000;

	if (!timeout_configured) {
		repo_config_get_int(the_repository, "core.packedrefstimeout", &timeout_value);
		timeout_configured = 1;
	}

	/*
	 * Note that we close the lockfile immediately because we
	 * don't write new content to it, but rather to a separate
	 * tempfile.
	 */
	if (hold_lock_file_for_update_timeout(
			    &refs->lock,
			    refs->path,
			    flags, timeout_value) < 0) {
		unable_to_lock_message(refs->path, errno, err);
		return -1;
	}

	if (close_lock_file_gently(&refs->lock)) {
		strbuf_addf(err, "unable to close %s: %s", refs->path, strerror(errno));
		rollback_lock_file(&refs->lock);
		return -1;
	}

	/*
	 * There is a stat-validity problem might cause `update-ref -d`
	 * lost the newly commit of a ref, because a new `packed-refs`
	 * file might has the same on-disk file attributes such as
	 * timestamp, file size and inode value, but has a changed
	 * ref value.
	 *
	 * This could happen with a very small chance when
	 * `update-ref -d` is called and at the same time another
	 * `pack-refs --all` process is running.
	 *
	 * Now that we hold the `packed-refs` lock, it is important
	 * to make sure we could read the latest version of
	 * `packed-refs` file no matter we have just mmap it or not.
	 * So what need to do is clear the snapshot if we hold it
	 * already.
	 */
	clear_snapshot(refs);

	/*
	 * Now make sure that the packed-refs file as it exists in the
	 * locked state is loaded into the snapshot:
	 */
	get_snapshot(refs);
	return 0;
}