Re: pages already locked on ia64

[Andrew Morton <akpm@osdl.org>]

Christian Hinkelbein <hinkelbein@ti.uni-mannheim.de> wrote:
>
> David Mosberger schrieb:
> 
> >>>>>>On Fri, 14 Nov 2003 11:22:23 +0100, Christian Hinkelbein <hinkelbein@ti.uni-mannheim.de> said:
> > 
> >   Christian> On ia32 i succesfully do a lock_page() on every page
> >   Christian> returned by get_user_pages(), lateron i do unlock_page().
> >   Christian> On ia64 sometimes (on ia32 seemingly never) the first
> >   Christian> page is already locked, just after malloc().  For a quick
> >   Christian> hack ......
> > 
> > Umh, what page-size did you use?
> > 
> > In any case, a minimal test-program that reproduces the problem would
> > probably help you get an answer much faster.
> 
> Uuuh, thanks for the hint. It was the bigger page-size (16k) that 
> triggered an old bug in my driver.
> 

Your driver is still buggy - you usually cannot lock more that one page at
a time.  Trivial case: mmap the same page of a file at two consecutive
addresses and ask your driver to access that 2*PAGE_SIZE chunk of memory. 
It will deadlock.

If you wish to make sure that the pages don't go away then elevating their
refcount is sufficient.