flock

fn flock(
    ev: *Evented,
    sync: *CancelRegion.Sync,
    fd: fd_t,
    op: File.Lock,
    blocking: enum { blocking, nonblocking },
) (File.LockError || error{WouldBlock})!void {
    while (true) {
        try sync.cancel_region.await(.nothing);
        switch (linux.errno(linux.flock(fd, LOCK.NB | @as(i32, switch (op) {
            .none => LOCK.UN,
            .shared => LOCK.SH,
            .exclusive => LOCK.EX,
        })))) {
            .SUCCESS => return,
            .INTR => {},
            .BADF => |err| return errnoBug(err),
            .INVAL => |err| return errnoBug(err), // invalid parameters
            .NOLCK => return error.SystemResources,
            .AGAIN => {
                const thread = try sync.cancel_region.awaitIoUring();
                thread.enqueue().* = .{
                    .opcode = .NOP,
                    .flags = 0,
                    .ioprio = 0,
                    .fd = 0,
                    .off = 0,
                    .addr = 0,
                    .len = 0,
                    .rw_flags = 0,
                    .user_data = @intFromPtr(sync.cancel_region.fiber),
                    .buf_index = 0,
                    .personality = 0,
                    .splice_fd_in = 0,
                    .addr3 = 0,
                    .resv = 0,
                };
                ev.yield(null, .nothing);
                switch (sync.cancel_region.errno()) {
                    .SUCCESS, .INTR, .CANCELED => {},
                    else => unreachable,
                }
                switch (blocking) {
                    .blocking => continue,
                    .nonblocking => return error.WouldBlock,
                }
            },
            .OPNOTSUPP => return error.FileLocksUnsupported,
            else => |err| return unexpectedErrno(err),
        }
    }
}