fix: add SAFETY message to kernel and remove unnecessary imports

Author: madhav-madhusoodanan

samples/introduction/async_api/kernels/src/lib.rs

@@ -1,6 +1,8 @@
 use cuda_std::prelude::*;
 
 #[kernel]
+// SAFETY: The user must ensure that the number of (threads * blocks * grids)
+// must not be greater than the number of elements in `g_data`.
 pub unsafe fn increment(g_data: *mut u32, inc_value: u32) {
     // This can also be obtained directly as
     //

samples/introduction/async_api/src/main.rs

@@ -1,12 +1,11 @@
-use cust::context::Context;
 use cust::device::Device;
 use cust::event::{Event, EventFlags};
 use cust::function::{BlockSize, GridSize};
+use cust::launch;
 use cust::memory::{AsyncCopyDestination, DeviceBuffer, LockedBuffer};
 use cust::module::Module;
 use cust::prelude::EventStatus;
 use cust::stream::{Stream, StreamFlags};
-use cust::{CudaFlags, launch};
 use std::time::Instant;
 
 static PTX: &str = include_str!(concat!(env!("OUT_DIR"), "/kernels.ptx"));