lkml.org 
[lkml]   [2001]   [Feb]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: x86 ptep_get_and_clear question
On Thu, 15 Feb 2001, Kanoj Sarcar wrote:

> No. All architectures do not have this problem. For example, if the
> Linux "dirty" (not the pte dirty) bit is managed by software, a fault
> will actually be taken when processor 2 tries to do the write. The fault
> is solely to make sure that the Linux "dirty" bit can be tracked. As long
> as the fault handler grabs the right locks before updating the Linux "dirty"
> bit, things should be okay. This is the case with mips, for example.
>
> The problem with x86 is that we depend on automatic x86 dirty bit
> update to manage the Linux "dirty" bit (they are the same!). So appropriate
> locks are not grabbed.

Will you please go off and prove that this "problem" exists on some x86
processor before continuing this rant? None of the PII, PIII, Athlon,
K6-2 or 486s I checked exhibited the worrisome behaviour you're
speculating about, plus it is logically consistent with the statements the
manual does make about updating ptes; otherwise how could an smp os
perform a reliable shootdown by doing an atomic bit clear on the present
bit of a pte?

-ben

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:15    [W:0.064 / U:0.692 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site