Re: [Qemu-devel] [PATCH v2 06/45] block: add support for job pause/resume

[Paolo Bonzini]

Il 27/09/2012 14:18, Kevin Wolf ha scritto:
>> > 
>> > Signed-off-by: Paolo Bonzini <address@hidden>
> I think there's a problem with terminology at least. What does "paused"
> really mean? Is it that the job has been requested to pause, or that it
> has actually yielded and is inactive?
> 
> The commit message seems to use the latter semantics (which I would
> consider the intuitive one),

You mean this: "Paused jobs cannot be canceled without first resuming
them".  I can add a specification, like "(even if the job actually has
not reached the sleeping point and thus is still running)".

> the QMP documentation leaves it unclear,
> but the code actually implements the former semantics.

This code comment is clear:

    /**
     * Set to true if the job is either paused, or will pause itself
     * as soon as possible (if busy == true).
     */
    bool paused;

but this one can indeed use some improvement.

/**
 * block_job_is_paused:
 * @job: The job being queried.
 *
 * Returns whether the job is currently paused.
 */
bool block_job_is_paused(BlockJob *job);


>From the QMP client's point of view it doesn't really matter, does it?

- even after a job that writes to disk X has "really" paused, you cannot
read or write disk X.  It's still owned by QEMU, it hasn't been flushed,
it may play games like lazy refcounts.

- what matters is that a resume undoes a pause, even if it is still
pending (which it does).

Paolo