linux-kernel - Re: [RFC PATCH v4 01/13] ktask: add documentation

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Message-ID: <20181106205146.GB30490@mellanox.com>
Date:   Tue, 6 Nov 2018 20:51:54 +0000
From:   Jason Gunthorpe <jgg@...lanox.com>
To:     Daniel Jordan <daniel.m.jordan@...cle.com>
CC:     Peter Zijlstra <peterz@...radead.org>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
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Subject: Re: [RFC PATCH v4 01/13] ktask: add documentation

On Tue, Nov 06, 2018 at 12:34:11PM -0800, Daniel Jordan wrote:

> > What isn't clear is if this calling thread is waiting or not. Only do
> > this inheritance trick if it is actually waiting on the work. If it is
> > not, nobody cares.
> 
> The calling thread waits.  Even if it didn't though, the inheritance trick
> would still be desirable for timely completion of the job.

Can you make lockdep aware that this is synchronous?

ie if I do

  mutex_lock()
  ktask_run()
  mutex_lock()

Can lockdep know that all the workers are running under that lock?

I'm thinking particularly about rtnl_lock as a possible case, but
there could also make some sense to hold the read side of the mm_sem
or similar like the above.

Jason