Re: swsusp vs pgdir

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > Wait... wait... If the whole linear mapping isn't mapped by this flat
> > pgdir, then we have a problem, since the MMU will have to go down the
> > kernel pagetables to actually access the pages data when copying them
> > around... but at this point, we are overriding the boot kernel page
> > tables with the loader ones, so ...
> 
> A new pgdir is allocated on resume that does not overlap with any pages
> being restored. See relocate_pagedir() in the code..

Perhaps this should serve as a warning to people trying to understand
swsusp.c?

								Pavel

--- tmp/linux/kernel/power/swsusp.c	2004-01-23 17:59:36.000000000 +0100
+++ linux/kernel/power/swsusp.c	2004-01-23 17:58:58.000000000 +0100
@@ -107,6 +107,10 @@
    time of suspend, that must be freed. Second is "pagedir_nosave", 
    allocated at time of resume, that travels through memory not to
    collide with anything.
+
+   Warning: this is even more evil than it seems. Pagedirs this files
+   talks about are completely different from page directories used by
+   MMU hardware.
  */
 suspend_pagedir_t *pagedir_nosave __nosavedata = NULL;
 static suspend_pagedir_t *pagedir_save;

-- 
When do you have a heart between your knees?
[Johanka's followup: and *two* hearts?]