Re: what is the state of current after an mm_fault occurs?

[Andrew Morton <akpm@osdl.org>]

Christoph Lameter <clameter@engr.sgi.com> wrote:
>
> On Wed, 4 Jan 2006, Andrew Morton wrote:
> 
> > >  You mean in some pagefault place we do schedule()?
> > 
> > We used to - that should no longer be the case.  The TASK_RUNNING thing is
> > probably redundant now.
> 
> The page fault handler calls the page allocator in various places 
> which may sleep. 

That's OK - they should all do set_current_state() before sleeping.  It's
the bare schedule() without previously setting TASK_foo which is the
problem.  We used to do that sort of thing in 2.4 as a lame yield point but
we really shouldn't be doing that at all anywhere any more.

> current may not point to the current process if the page fault handler was 
> called from get_user_pages.

current always points at the current process.  In the situation
ptrace->access_process_vm->get_user_pages->pagefault we'll have mm !=
current->mm.