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    SubjectRe: [RFC][PATCH -mm 3/3] PM: Disable _request_firmware before hibernation/suspend
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    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.

    Kay

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