[linux-pm] [suspend/resume] Re: userspace notification from module
Rafael J. Wysocki
rjw at sisk.pl
Tue Jan 5 15:03:23 PST 2010
On Tuesday 05 January 2010, Bartłomiej Zimoń wrote:
> Dnia 5 stycznia 2010 22:23 "Rafael J. Wysocki" <rjw at sisk.pl> napisał(a):
> > On Tuesday 05 January 2010, Bartłomiej Zimoń wrote:
> > > Dnia 5 stycznia 2010 10:07 Anders Eriksson <aeriksson at fastmail.fm> napisał(a):
> > > >
> > > > rjw at sisk.pl said:
> > > > >> > I don't see a problem with this in principle, although I don't think signals
> > > > >> > are very suitable for this particular purpose, because you need two-way
> > > > >> > communication between the power manager and the processes it's going to
> > > > >> > notify (because it has to wait for the processes to finish their preparations
> > > > >> > and to tell it that they are ready).
> > > >
> > > > Wouldn't there need to be dependecy tracking for the userspace processes? A
> > > > process couldn't signal "done" until it know there's no more work to do, which
> > > > requires all other processes to finish up first.
> > > >
> > >
> > > Not all processes will need pm notification.
> > >
> > > Just in case, could this "power manager" be provided as userspace
> > > driver for kernel (for example compiled as UIO)?
> > I don't really understand why you want to do that in the kernel. Is there
> > any particular reason why this cannot be done in the user space?
> Problem is with notification from pm-utils. Dbus for session is only
> user session waid and it is almost imposible to send something
> from systembus or it needs lots of magic.
Don't use dbus, then.
> Even if i'll use pm-utils, must provide way to notify my app.
> Looks like no standard way here, that's bad, every app has it's own?
Isn't there a possibility to introduce a standard way of doing that without
involving the kernel directly?
> I think this way - if kernel is processes manager and if it sends
> "some unknown" signal to every process before kernel suspend so why
> not send sepcific and known signal instread.
We _can_ do that, but what would a process be supposed to do after receiving
such a signal?
> But now we have DeviceKit-power/upower whatever but it doesn't provide
> this feature or something simmilar to relay on.
You're still not saying what you really need. So, what's the application you
have in mind that needs a notification from the _kernel_ so badly?
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