Re: mlockall and mmap of IO devices don't mix

[Andrew Morton <akpm@osdl.org>]

Joe Korty <joe.korty@ccur.com> wrote:
>
> > Something like this?
> 
> 
> Sigh.  No go; it *looks* good but my app still locks up....

Oh crap, you're mapping /dev/mem rather than going through a device driver.
/dev/mem isn't setting VM_IO.

Does this little experiment make it go?


diff -puN drivers/char/mem.c~a drivers/char/mem.c
--- 25/drivers/char/mem.c~a	Fri Oct  3 16:04:04 2003
+++ 25-akpm/drivers/char/mem.c	Fri Oct  3 16:04:15 2003
@@ -176,7 +176,7 @@ static int mmap_mem(struct file * file, 
 	/*
 	 * Don't dump addresses that are not real memory to a core file.
 	 */
-	if (uncached)
+//	if (uncached)
 		vma->vm_flags |= VM_IO;
 
 	if (remap_page_range(vma, vma->vm_start, offset, vma->vm_end-vma->vm_start,

_

Course I could test it myself...


I wonder what to do.  Perhaps /dev/mam should set VM_IO if any of the
mapped pages are not valid mem_map-style pageframes.  Or maybe it should
just set VM_IO all the time.