Re: [linux-usb-devel] Re: hotplugging to deal with firmware download

[Oliver Neukum <oliver@neukum.name>]

Am Sonntag, 2. Juni 2002 13:11 schrieb Brad Hards:
> On Mon, 3 Jun 2002 00:44, Oliver Neukum wrote:
> > Am Sonntag, 2. Juni 2002 01:16 schrieben Sie:
> > > On Sun, 2 Jun 2002 02:07, Oliver Neukum wrote:
> > > > The problem is that this cannot simply work, because a filesystem
> > > > may be mounted by nfs.
> > >
> > > How is this a problem? You simply need to bring the driver up before
> > > you remount the nfs filesystem. If you assume that your firmware is
> > > on that filesystem, then you couldn't have mounted it in the first
> > > place.
> > >
> > > What am I missing here?
> >
> > Paging. As soon as user space is running, dirty pages may be written
> > out And in order to run a user space firmware loader, user space must
> > be functional, or am I overlooking something?
>
> The software support option requires swap to store to, right? That had
> better be on a local disk, or it doesn't matter whether the firmware is
> in userspace or not. Realistically, swap over a network block device
> isn't a problem worth trying to solve.

Not only swap, but any file opened for writing may be written to
if you allocate memory.

> > Thus as soon as you do something that allocates memory from user
> > space, you may deadlock IMHO.
>
> If you are going to get the firmware from disk (per your alternative
> suggestion), how is that going to help avoid the malloc?

If I load the firmware in kernel I can allocate memory with GFP_NOFS.

	Regards
		Oliver


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