Re: [UNIKRAFT PATCH] include: Introduce uk/preemmpt.h

[Costin Lupu <costin.lupu@xxxxxxxxx>]

Hi Alexander,

As agreed offline, I'll add on upstreaming `uk_` prefixes.

Reviewed-by: Costin Lupu <costin.lupu@xxxxxxxxx>

On 7/23/20 12:38 PM, Alexander Jung wrote:
> This commit adds an additional header with two new methods:
> 
>  - preempt_disable()
>  - preempt_enable()
> 
> These methods enable and disable preemption by calling a memory
> barrier only.  Their names are derived from the Linux Kernel[1].
> 
> Whilst currently unimplemented, pre-emptive scheduling requires
> additional notarization when called.  This means that future
> enhancements to Unikraft's pre-emptive scheduler will need to
> modify these methods to increase a counter within the thread
> to indicate whether the thread is pre-emptible or not.
> 
> [0]: 
> https://elixir.bootlin.com/linux/latest/source/include/linux/preempt.h#L169
> 
> Signed-off-by: Alexander Jung <alexander.jung@xxxxxxxxx>
> ---
>  include/uk/preempt.h | 40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
>  create mode 100644 include/uk/preempt.h
> 
> diff --git a/include/uk/preempt.h b/include/uk/preempt.h
> new file mode 100644
> index 0000000..d45623d
> --- /dev/null
> +++ b/include/uk/preempt.h
> @@ -0,0 +1,40 @@
> +/* SPDX-License-Identifier: BSD-3-Clause */
> +/*
> + * Authors: Alexander Jung <alexander.jung@xxxxxxxxx>
> + *
> + * Copyright (c) 2020, NEC Laboratories Europe GmbH, NEC Corporation.
> + *                     All rights reserved.
> + *
> + * Redistribution and use in source and binary forms, with or without
> + * modification, are permitted provided that the following conditions
> + * are met:
> + *
> + * 1. Redistributions of source code must retain the above copyright
> + *    notice, this list of conditions and the following disclaimer.
> + * 2. Redistributions in binary form must reproduce the above copyright
> + *    notice, this list of conditions and the following disclaimer in the
> + *    documentation and/or other materials provided with the distribution.
> + * 3. Neither the name of the copyright holder nor the names of its
> + *    contributors may be used to endorse or promote products derived from
> + *    this software without specific prior written permission.
> + *
> + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS 
> IS"
> + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
> + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
> + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
> + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
> + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
> + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
> + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
> + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
> + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
> + * POSSIBILITY OF SUCH DAMAGE.
> + */
> +
> +#ifndef __UK_PREEMPT_H__
> +#define __UK_PREEMPT_H__
> +
> +#define preempt_disable()    barrier()
> +#define preempt_enable()     barrier()
> +
> +#endif /* __UK_PREEMPT_H__ */
>