On Thu, 2011-08-11 at 14:02 +0200, Peter Zijlstra wrote:

On Thu, 2011-08-11 at 13:30 +0200, Tim Sander wrote:

quoted

The error does not occur  when configured with 
CONFIG_PREEMPT_RT_FULL=y
but with 
CONFIG_PREEMPT_RTB=y.
The same error also happens with
CONFIG_PREEMPT_LL=y. (A log is appended after the other log just
search for CONFIG_PREEMPT_LL 
for starting point). 

Does the below (on top of -rt8) cure things for you? Shouldn't make a
difference for PREEMPT_LL though, so maybe there's something else busted
as well. But from what I can tell PREEMPT_BASE should be fine with such
things disabling preemption..

Gah, nevermind, I'm sleeping or so..

---
Index: linux-2.6/mm/filemap.c
===================================================================

--- linux-2.6.orig/mm/filemap.c
+++ linux-2.6/mm/filemap.c

@@ -2040,7 +2040,7 @@ size_t iov_iter_copy_from_user_atomic(st
 	char *kaddr;
 	size_t copied;
 
-	BUG_ON(!current->pagefault_disabled);
+	BUG_ON(!(in_atomic() || current->pagefault_disabled));
 	kaddr = kmap_atomic(page, KM_USER0);
 	if (likely(i->nr_segs == 1)) {
 		int left;