Re: [PATCH 1/4] sched: move IO scheduling accounting from io_schedule_timeout() to __schedule()

[Peter Zijlstra]

On Fri, Oct 28, 2016 at 03:12:32PM -0400, Tejun Heo wrote:
> Hello, Peter.
> 
> On Fri, Oct 28, 2016 at 09:07:02PM +0200, Peter Zijlstra wrote:
> > One alternative is to inherit the iowait state of the task we block on.
> > That'll not get rid of the branches much, but it will remove the new
> > mutex APIs.
> 
> Yeah, thought about that briefly but we don't necessarily track mutex

This one I actually fixed and should be in -next. And it would be
sufficient to cover the use case here.

> or other synchronization construct owners, things get gnarly with
> rwsems (the inode ones sometimes end up in a similar situation), and
> we'll probably end up dealing with some surprising propagations down
> the line.

rwsems could be done for writers only.