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SubjectRe: [PATCH #2] console lock grabbed too early in printk...

As I mentioned earlier... this assumes that copy_from_user is not a simple
memcpy, or that copy_from_user does not induce the page fault... which
would induce precisely the same problem that I'm seeing. Either way, the
root problem is unchanged.

-Chris


On Sun, 2 Jul 2000, Russell King wrote:

> Chris Lattner writes:
> > The sequence of events goes like this:
> > 1. printk of args to sys_access
> > 2. printk grabs the console lock
> > 3. vfprintf is called, but one of the strings (the filename) resides on a
> > page that hasn't been materialized yet.
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> This is the real bug.
>
> > 4. page fault occurs
> > 5. page fault handler runs, maps page
> > 6. Page mapping causes printk
> > 7. printk causes deadlock as it attempts to grab the console lock that the
> > kernel thread already has...
>
> printk is not broken. Your debug code is.
> _____
> |_____| ------------------------------------------------- ---+---+-
> | | Russell King rmk@arm.linux.org.uk --- ---
> | | | | http://www.arm.linux.org.uk/~rmk/aboutme.html / / |
> | +-+-+ --- -+-
> / | THE developer of ARM Linux |+| /|\
> / | | | --- |
> +-+-+ ------------------------------------------------- /\\\ |
>


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