Re: [Xen-devel] [PATCH 3/6] xen/sched: Improvements to the {alloc, free}_domdata() interfaces

[Meng Xu <xumengpanda@xxxxxxxxx>]

On Wed, Feb 28, 2018 at 9:14 AM, Andrew Cooper
<andrew.cooper3@xxxxxxxxxx> wrote:
>
> The main purpose of this change is for the subsequent cleanup it enables, but
> it stands on its own merits.
>
> In principle, these hooks are optional, but the SCHED_OP() default aliases a
> memory allocation failure, which causes arinc653 to play the dangerous game of
> passing its priv pointer back, and remembering not to actually free it.
>
> Redefine alloc_domdata to use ERR_PTR() for errors, NULL for nothing, and
> non-NULL for a real allocation, which allows the hook to become properly
> optional.  Redefine free_domdata to be idempotent.
>
> For arinc653, this means the dummy hooks can be dropped entirely.  For the
> other schedulers, this means returning ERR_PTR(-ENOMEM) instead of NULL for
> memory allocation failures, and modifying the free hooks to cope with a NULL
> pointer.  While making the alterations, drop some spurious casts to void *.
>
> Introduce and use proper wrappers for sched_{alloc,free}_domdata().  These are
> strictly better than SCHED_OP(), as the source code is visible to
> grep/cscope/tags, the generated code is better, and there can be proper
> per-hook defaults and checks.
>
> Callers of the alloc hooks are switched to using IS_ERR(), rather than
> checking for NULL.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---


Acked-by: Meng Xu <mengxu@xxxxxxxxxxxxx>


Thanks,


Meng

-----------
Meng Xu
Ph.D. Candidate in Computer and Information Science
University of Pennsylvania
http://www.cis.upenn.edu/~mengxu/

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