On Sunday, 8 July 2007 23:03, Benjamin Herrenschmidt wrote: > On Sun, 2007-07-08 at 21:15 +0200, Rafael J. Wysocki wrote: > > On Sunday, 8 July 2007 07:14, Benjamin Herrenschmidt wrote: > > [--snip--] > > > > > > I just think that the freezer approach, as it is, is backward. We can't > > > have a 3rd party try to discriminate what to freeze and what not, it > > > will always get something wrong, and in some cases with the wrong timing > > > or ordering. > > > > Nice discussion, except for one thing: the freezer doesn't decide what to > > freeze. For example, even right now kernel threads decide if they want to be > > frozen. > > Somewhat... userspace doesn't and workqueues are a gray area. Workqueues are kernel threads and the creator decides if they are going to freeze. There are only two freezable worqueues in the entire tree right now. > Also, I've been thinking this "icebox" idea a bit more and it seems in > fact a bit racy in some areas, at least for use by things like drivers, > unless we end up doing something aking to an RCU on suspend, waiting for > all tasks to reach userland once, but that has the same annoyances as > the current freezer. > > Thus I'm tempted to go back to saying that driver can handle things > locally :-) Actaully, I'm perfectly fine with that, as long as each task blocked by the driver due to suspend has PF_FROZEN (or something similar) set. Then, at least theoretically, we'll be able to drop the freezer from the suspend code path and move it after device_suspend() (or the hibernation-specific equivalent) for hibernation (in that case there shouldn't be a problem with any task waiting on I/O while the freezer is running ;-)). Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
