Re: [PATCH 01/13] PM: Add wake lock api.

Pavel Machek
2009-02-27T20:32:52Z

On Fri 2009-02-27 15:07:14, Uli Luckas wrote:
> On Friday, 27. February 2009, Pavel Machek wrote:
> > On Fri 2009-02-13 17:49:57, Uli Luckas wrote:
> > > On Friday, 13. February 2009, Matthew Garrett wrote:
> > > > Userland ABI would then be a single /dev/inhibit_suspend,
> > > > with the counter being bumped each time an application opens it. It'll
> > > > automatically be dropped if the application exits without cleaning up.
> > > >
> > > > This seems simpler and also avoids any arguments about the naming
> > > > scheme. What am I missing?
> > >
> > > Opening and closing an fd sounds like a lot of overhead. Taking and
> > > releasing locks if going to be a called with very highg frequency. I'd go
> > > for an ioctl.
> >
> > Ehm?
> >
> > And introduce nasty interface, and probably slower too since open() is
> > time-critical and ioctl() is not? Or do you have benchmarks?
>
> No, just specualting as open() needs to do a directory lookup. It also needs
> to do book keeping. I'd be surprised if open was faster then ioctl.

Unless you measure how much slower it is...

> On the otherhand if you consider ioctl nasty, maybe write() is an option?

You want sleepvetos to be automatically unlocked/freed on close and
process exit/kill, so neither write nor ioctl is the right interface.

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