lkml.org 
[lkml]   [2020]   [Dec]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [MOCKUP] x86/mm: Lightweight lazy mm refcounting
From
Date
On Thu, 2020-12-03 at 12:31 +0000, Matthew Wilcox wrote:

> And this just makes me think RCU freeing of mm_struct. I'm sure it's
> more complicated than that (then, or now), but if an anonymous
> process
> is borrowing a freed mm, and the mm is freed by RCU then it will not
> go
> away until the task context switches. When we context switch back to
> the anon task, it'll borrow some other task's MM and won't even
> notice
> that the MM it was using has gone away.

One major complication here is that most of the
active_mm borrowing is done by the idle task,
but RCU does not wait for idle tasks to context
switch.

That means RCU, as it is today, is not a
mechanism that mm_struct freeing could just
piggyback off.

--
All Rights Reversed.
[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2020-12-03 15:28    [W:0.066 / U:0.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site