lkml.org 
[lkml]   [2022]   [Dec]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [GIT PULL] x86/mm for 6.2
On Thu, Dec 15, 2022 at 9:17 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Here's *one* suggested solution:

Note again: this is not a "you need to do it this way" suggestion.
This is just a "at least this way doesn't have the issues I object
to". There are bound to be other ways to do it.

But if you feel like all threads have to share the same LAM state, it
does seem a lot simpler if you just say "you need to set that state
before you start any threads". No?

> And yes, I would actually suggest that _any_ thread creation locks it,
> so that you never *EVER* have any issues with "oh, now I need to
> synchronize with other threads". A process can set its LAM state at
> startup, not in the middle of running!

Note that this "no serialization needed" is just about the SW side.

The *hardware* side may still need the IPI just to make sure that it
forces a TLB flush - even if we are single-threaded, that single
thread may have run on other CPU's before.

But I think at that point it's just a regular TLB flush, and doesn't
need that LAM-specific IPI.

But maybe there's some bigger HW serialization that is needed for the
LAM bit, I have not looked at that enough to know.

Linus

\
 
 \ /
  Last update: 2022-12-15 18:26    [W:0.089 / U:0.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site