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From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <bf511ee2-c1da-1953-4f3c-f53b07ed5211@redhat.com>
Date: Thu, 16 Jun 2016 15:24:43 +0200
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Subject: Re: [Qemu-devel] [PATCH v4 2/5] blockjob: add pause points
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>, qemu-devel <qemu-devel@nongnu.org>, Kevin Wolf <kwolf@redhat.com>, Jeff Cody <jcody@redhat.com>, Fam Zheng <famz@redhat.com>, "Jason J. Herne" <jjherne@linux.vnet.ibm.com>, Max Reitz <mreitz@redhat.com>



On 16/06/2016 15:17, Stefan Hajnoczi wrote:
>> Right, we should document job->busy as a quiescent state where no one
>> will re-enter the coroutine.
> 
> That statement doesn't correspond with how it's used:
> 
> block_job_sleep_ns() leaves a timer pending and the job will re-enter
> when the timer expires.  So "no one will re-enter the coroutine" is
> too strict.

And of course you're right. :)  What I (sloppily) meant was "where the
block job code will not re-enter the coroutine", which is what makes it
safe to call block_job_enter().

> The important thing is it's safe to call block_job_enter().  In the
> block_job_sleep_ns() case the timer is cancelled to prevent doubly
> re-entry.
> 
> The doc comment I have in v4 allows the block_job_sleep_ns() case:
> 
>   /*
>    * Set to false by the job while the coroutine has yielded and may be
>    * re-entered by block_job_enter().  There may still be I/O or event loop
>    * activity pending.
>    */
>   bool busy;

Sounds good!

Paolo