Re: [patch] pipe: Don't oops when pipe filesystem isn't mounted

[Andrew Morton]

On Mon, 11 Dec 2006 09:33:15 +0000
Al Viro <viro@xxxxxxxxxxxxxxxx> wrote:

> On Mon, Dec 11, 2006 at 01:25:45AM -0800, Andrew Morton wrote:
> > On Mon, 11 Dec 2006 09:21:30 +0000
> > Al Viro <viro@xxxxxxxxxxxxxxxx> wrote:
> > 
> > > On Mon, Dec 11, 2006 at 01:13:27AM -0800, Andrew Morton wrote:
> > > > On Mon, 11 Dec 2006 00:55:57 -0800
> > > > Andrew Morton <akpm@xxxxxxxx> wrote:
> > > > 
> > > > > I think the bug really is the running of populate_rootfs() before running
> > > > > the initcalls, in init/main.c:init().  It's just more sensible to start
> > > > > running userspace after the initcalls have been run.  Statically-linked
> > > > > drivers which want to load firmware files will lose.  To fix that we'd need
> > > > > a new callback.  It could be with a new linker section or perhaps simply a
> > > > > notifier chain.
> > > > 
> > > > hm, actually...  Add two new initcall levels, one for populate_rootfs() and
> > > > one for things which want to come after it (ie: drivers which want to
> > > > access the filesytem):
> > > 
> > > IMO we should just call pipe (and socket) initialization directly at
> > > the same level as slab, task, dcache, etc.
> > 
> > spose that would work.  But what other initcall-initialised things are not
> > yet available when populate_rootfs() runs?
> > 
> > <does  grep _initcall */*.c>
> > <wonders why anything works at all>
> 
> Explain, please...

- populate_rootfs() puts stuff into the filesystem

- we then run initcalls.

- an initcall runs /sbin/hotplug.

We're now running userspace before all the initcalls have been executed. 
Hence we're trying to run userspace when potentially none of "grep
_initcall */*.c" has been executed.  It isn't a kernel yet...

See http://marc.theaimsgroup.com/?l=linux-kernel&m=116510389000878&w=2
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