On Mon, 2008-04-14 at 11:13 -0400, Alan Stern wrote: > 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? Despite what Oliver says, that's a perfect example where the module load syscalls should return an error. Maybe something like -EAGAIN would do tho... that might need a minor update of the module init tools so they retry instead of failing. Ben. -- 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
