Re: [RFC PATCH 11/15] jobs: remove aiocontext locks since the functions are under BQL

[Emanuele Giuseppe Esposito <eesposit@redhat.com>]

On 02/11/2021 13:41, Vladimir Sementsov-Ogievskiy wrote:
> Hmm. subject looks like it's safe to remove aiocontext locks from any 
> qmp command?
> 
> For example, commit 91005a495e228eb added aiocontext locks back to qmp 
> bitmap add/remove commands because otherwise they crashed.
> 
> So, I'm not sure that being under BQL is enough to drop aiocontext 
> locking..
> 
> 

In this specific case the aiocontext is useless there. I am not sure 
what it was used for before, but if you look at what it protects in this 
patch we have:

- block_job_query: not called by anyone else, and internally calls:
	* block_job_is_internal = checks struct job id, that is only written at 
job initialization
	* progress_get_snapshot = we made it thread safe, as you might remember
	* accesses struct job fields, that we protect anyways with job_mutex. 
Anyways the aiocontext is not used to protect jobs fields.

- job_query_single: same as block_job_query, calls progress_get_snapshot 
and accesses job fields.

So yes, I am positive that here removing the aiocontext lock does not 
break anything.

Thank you,
Emanuele