On Thu, May 27, 2010 at 04:36:28PM -0700, Arve Hjønnevåg wrote: > 2010/5/27 Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>: > > On Wed, May 26, 2010 at 05:52:40PM -0700, Arve Hjønnevåg wrote: > >> 2010/5/26 Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>: > >> > On Wed, 26 May 2010, Arve Hjønnevåg wrote: > >> > > >> >> > I must be missing something. In Arve's patch 1/8, if the system is in > >> >> > opportunistic suspend, and a wakeup event occurs but no suspend > >> >> > blockers get enabled by the handler, what causes the system to go back > >> >> > into suspend after the event is handled? Isn't that a loop of some > >> >> > sort? > >> >> > > >> >> > >> >> Yes it is a loop. I think what you are missing is that it only loops > >> >> repeatedly if the driver that aborts suspend does not use a suspend > >> >> blocker. > >> > > >> > You mean "the driver that handles the wakeup event". I was asking what > >> > happened if suspend succeeded and then a wakeup occurred. But yes, if > >> > a suspend blocker is used then its release causes another suspend > >> > attempt, with no looping. > >> > > >> >> > And even if it isn't, so what? What's wrong with looping behavior? > >> >> > >> >> It is a significant power drain. > >> > > >> > Not in the situation I was discussing. > >> > > >> > >> If you meant it spend most of the time suspended, then I agree. It > >> only wastes power when a driver blocks suspend by returning an error > >> from its suspend hook and we are forced to loop doing no useful work. > >> > > > > If driver refuses to suspend that means there are events that need > > processing. I fail to see why it would be called "looping doing no > > useful work". > > Because the useful work is done in another thread. All the loop does > is check if the useful work has completed which most likely will slow > down the useful work. Or useful work could signal when it is done processing critical section. > Blocking suspend with a suspend blocker until > the useful work is done is more efficient. > -- Dmitry _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
