On Mon 2007-05-28 13:24:53, Kay Sievers wrote: > On Mon, 2007-05-28 at 13:15 +0200, Pavel Machek wrote: > > Hi! > > > > > > > > What exactly is the problem we see here? The timeout of the firmware loader? > > > > > > What goes wrong with frozen userspace, usually there is only a netlink > > > > > > message sent from the kernel, which should be received and handled > > > > > > just fine when userspace is running again. > > > > > > > > > > Driver calls request_firmware in the resume method. The userspace helper > > > > > can't be run because it's been frozen, so the firmware never gets loaded > > > > > and the call times out. The driver then fails to resume. While all this > > > > > is happening, the rest of the kernel is blocking on that resume method. > > > > > The firmware can be loaded once userspace has been started again, but by > > > > > that time the driver has given up. > > > > > > > > Seems, that's just the broken synchronous firmware loading interface > > > > with the useless timeout handling. The nowait version of the same loader > > > > doesn't time out, and should not have that problem. The sync version > > > > should be removed from the kernel, it just causes all sorts of problems > > > > since it exists. > > > > > > > > Userspace should handle the async request just fine when it comes back > > > > running, regardless of the time it was submitted. > > > > > > Okay, so the solution is to convert the drivers to use > > > request_firmware_nowait() instead of request_firmware() in their .resume() > > > routines. > > > > You'll just get deadlock at different level (and more rare). > > > > Imagine disk with its firmware on NFS and NFS with its firmware on > > disk. > > > > (Or maybe firmware loader doing find /, including both disk and > > NFS). Just don't call request_firmware_* from .resume(). > > A driver for a bootup-critical device like this should just never > release the firmware after the first load. There is absolutely no point > in doing that. It does not have to be _bootup-critical_ device. Problem is any device that might be used by userspace firmware loader. And that is _any_ device. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
