On Mon, 14 Apr 2008, Rafael J. Wysocki wrote: > "you can assume that the user space is there while ->prepare() is running, > but you are supposed to prevent new children of the device from being > registered from that point on _and_ you have to make sure that freezable > tasks will be able to freeze after ->prepare() has run" (but why on Earth a > driver writer is now required to know what's a freezable task etc.?) This reminds me... We're going to need a way to make certain activities mutually exclusive with system sleep. The simplest example is loading a kernel module; init and probe routines often end up causing new child devices to be registered. The most straightforward approach is to use an rwsem like the one we used to have. However I'm concerned that under some circumstances there might be recursive read-locking. (For example, the init routine in a newly-loaded module decides to load yet another module. Can this actually happen? libusual does something much like it.) So it's quite possible we'll end up needing a mechanism that resembles an rwsem but allows recursive (properly nested) read-locking. Does such a thing exist already, or would it have to be invented? Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
