lkml.org 
[lkml]   [2010]   [May]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/2] mm: Take all anon_vma locks in anon_vma_lock
> > Btw, Mel's patch doesn't really match the description of 2/2. 2/2 says
> > that all pages must always be findable in rmap. Mel's patch seems to
> > explicitly say "we want to ignore that thing that is busy for execve". Are
> > we just avoiding a BUG_ON()? Is perhaps the BUG_ON() buggy?
>
> I have no good answer to this question.
>
> Mel? Andrea?

If try_to_unmap is allowed to establish the migration pte, then such
pte has to remain reachable through rmap_walk at all times after that,
or migration_entry_wait will crash because it notices the page has
been migrated already (PG_lock not set) but there is still a migration
pte established. (remove_migration_pte like split_huge_page isn't
allowed to fail finding all migration ptes mapping a page during the
rmap walk)

It's not false positive BUG_ON if that's what you mean, removing the
BUG_ON would still lead to infinite hang waiting on a migration pte
that shouldn't be there anymore.


\
 
 \ /
  Last update: 2010-05-03 20:17    [W:1.801 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site